Assignment Prompt & Instructions
– ## ConcentrationLabInstructions2025online-activities.pdf
– ## ConcentrationLabInstructions2025online-prelab.pdf
**## ConcentrationLabInstructions2025online-activities.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 2: Activities
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Activity 1: Molar Mass Calculations
For this activity, you will need the periodic table in Appendix A of the prelab.
Using the periodic table, determine the molar mass of the following compounds:
1. Cobalt(II) nitrate, Co(NO3)2
2. Cobalt(II) chloride, CoCl2
3. Potassium dichromate, K2Cr2O7
4. Potassium chromate, K2CrO4
5. Nickel(II) chloride, NiCl2
6. Copper(II) sulfate, CuSO4
7. Potassium permanganate, KMnO4
8. Sodium chloride, NaCl
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Activity 2: Saturated Solutions
For this activity, you will be using the Concentration simulation on the PhET website. The web address
for this simulation is given at the beginning of the lab handout under Web Links. You can also click here
to take you to the simulation. You are going to investigate the effect of varying the amount of solute,
solvent, and solution on the saturation of the solution.
1. Open the PhET Concentration Simulation.
2. Move the crosshairs end of the concentration meter into the solution. It will read 0.000 mol/L. Leave
the solute selection dropdown menu set to “Drink Mix”.Shake the solute shaker a few times. This will
add drink mix to the water. Notice the change in the concentration. In table 1, in the “Drink mix is
added” describe what happens to the concentration, e.g. remains the same, increases, decreases, goes
to zero.
3. Then add additional water to the solution. In table 1 column 3, describe what happens to the
concentration, e.g. remains the same, increases, decreases, goes to zero.
4. Adjust the evaporation slider, so that it is no longer set to “none”. Describe the effect on the
concentration of the solution in table 1 column 4.
5. Drain some (not all) of the solution and describe the effect on the concentration of the solution in table
1 column 5.
6. Click on the “Remove Solute” button and describe the effect on the concentration of the solution in
table 1 column 6.
Figure 1: PhET Concentration Simulation. The arrows point to the pieces that move and affect the concentration and or
amount of solution. The solute can be changed using the drop-down menu at the top right.
[https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html](https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html)
PHSC 1021 online 3 | P a g e
Table 1: Effect of Various Actions on the Concentration of a Solution
Action
Drink mix is
added
Water is added
Evaporation
occurs
Solution is drained
Solute is removed
What happens to
concentration?
7. Reset the simulation and insert the concentration meter into the solution.
8. Keep the solute to “Drink mix” and add as much as you can.
9. How do you know when a solution is saturated?
10. While the solution is saturated, add additional solid solute. What happens?
11. Why do you think this is?
12. How does adding this additional solute change the concentration of the saturated solution?
13. Increase the evaporation of the saturated solution. How does evaporation change the concentration of
the saturated solution?
Concentration
PHSC 1021 online 4 | P a g e
Activity 3: Solute Mass of Saturated Solutions
For this activity, you will continue using the Concentration simulation on the PhET website. You are
going to use the simulation to determine the saturation concentration of different solutes dissolved in
water. Then you will calculate the mass of the solute in the saturated solutions.
1. Reset the Concentration Simulation.
2. Fill the beaker to 1 L.
3. Keep the evaporation set to “none”, and place the concentration sensor in the solution.
4. For each solute in table 2, find and record the concentration when saturation occurs. (You can do this
by shaking the solute shaker until the word “saturated” appears. Then read the concentration on the
sensor.) Complete the second column of table 2 with your results.
Table 2: Concentration and Solute Mass for Various Solutes
Solute Concentration for
Saturation
(mol/L)
Solute Mass
(grams)
Drink mix
Cobalt (II) nitrate
Cobalt (II) chloride
Potassium dichromate
Potassium chromate
Nickel (II) chloride
Copper (II) sulfate
Potassium permanganate
Sodium chloride
5. Does each solute have the same concentration at saturation?
6. For each solute, determine the mass in grams required to saturate 1 L of solution. Record these
values in column 3 of the table 2. See example 6 in the prelab for a reminder of how to determine the
mass of a one liter saturated solution.
References
1. This lab was adapted from an activity provided by: University of Colorado. (). PhET Interactive
Simulations – Physics, PhET: Interactive simulations. Retrieved at May 7, 2020, from the website
https://phet.colorado.edu/en/contributions/view/4280
[https://phet.colorado.edu/en/contributions/view/4280](https://phet.colorado.edu/en/contributions/view/4280)
**## ConcentrationLabInstructions2025online-prelab.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 1: Prelab
Objectives:
• Explore concentration and saturation as related to solvents and solutes.
• Calculate molar mass and mass of solute needed for a specific concentration.
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Introduction:
A mixture is a type of matter composed of varying proportions of two or more substances that are only
physically mixed and not chemically combined. Mixtures can be divided into two categories –
heterogeneous and homogeneous. A heterogeneous mixture is non-uniform so that at least two
components can be observed examples include pizza and oil/water. A homogeneous mixture is uniform
throughout like coffee or an alloy. Another name for a liquid, homogeneous mixture is a solution. A
solution is composed of two parts 1) a solvent which is the liquid or the substance in the larger quantity,
and 2) a solute which is the substance dissolved in the solvent. Figure 1 below shows two examples of
salt-water solutions. In a salt-water solution, water is in the larger amount and is the solvent, while the
salt is in the smaller amount and is the solute. At a given temperature only a certain amount of solute can
be dissolved into the solvent. When the maximum amount of solute is present the solution is said to be
saturated. Any extra solute added to a saturated solution would remain undissolved and usually settle at
the bottom of the container. When less than the maximum amount of solute is dissolved into the solvent,
the solution is called unsaturated.
Figure 1: Two Examples of Salt-Water Solutions.
—————————————————————————————————————————–
Examples:
1. In a solution which substance is present in the larger amount, the solvent or the solute?
Solvent – The solvent is the liquid or the substance in the larger quantity
2. Take a cup of water, add sugar, and stir. If the resulting solution contains sugar crystals that do not
dissolve, is the solution saturated or unsaturated?
Unsaturated – If there is no precipitate at the bottom then it is likely less than the maximum amount of
the solute is present.
—————————————————————————————————————————–
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Moles and Molarity
In addition to the broad categories of saturated and unsaturated, solutions can be classified based on their
concentration or molarity. Molarity is the concentration of a solution expressed in the number of moles
of solute per liter of solution. In order to calculate the molarity of a solution, you need to know the
number of moles of solute and the total volume of the solution. Moles are used to measure the amount of
a substance. A mole is a number of somethings. The same way a dozen eggs means twelve eggs. A mole
of atoms is 6.02×1023 atoms. For this lab we will focus on a property of moles concerning mass. To
understand this property of moles, first we will talk about atomic mass and formula mass.
Chemical Formula and Number of Atoms
Compounds such as sodium chloride and water can be written out as words or a shorthand form of the
name can be written. This shorthand form is called the chemical formula. Look back at figure 1 and notice
that H2O is used instead of water. In the same figure NaCl is used instead of sodium chloride. The
chemical formula for a substance contains the chemical symbol for each element present. If there is more
than one atom of that element then a subscript will also be used in the chemical formula. The subscripts
show the number of atoms of that element. If there is a subscript 2, that means the compound contains two
atoms of that element. A subscript of 3 would mean the compound contains three atoms of that element.
H2O has two hydrogen atoms and one oxygen atom. NaCl has one sodium atom and one chlorine atom.
Copper(II) sulfate, CuSO4, has one copper atom, one sulfur atom, and four oxygen atoms.
The purpose of the chemical formula is to have a shorthand way of describing the compounds. Cobalt (II)
nitrate has the chemical formula Co(NO3)2. This signifies that one cobalt atom is bonded to two nitrate
ions. If we are counting atoms and parentheses are present, then we multiply the subscript times
everything in the parentheses. Therefore cobalt(II) nitrate has one cobalt atom, 2×1=2 nitrogen atoms, and
2×3=6 oxygen atoms.
—————————————————————————————————————————–
Examples:
3. The formula for potassium dichromate is K2Cr2O7. Which elements are present, and how many atoms
of each element are present in this compound?
2 K, 2 Cr, 7 O
Two atoms of potassium, two atoms of chromium, and seven atoms of oxygen
4. The formula for lead chromate is PbCrO4. Which elements are present, and how many atoms of each
element are present in this compound?
1 Pb, 1 Cr, 4 O
One atom of lead, one atom of chromium, and four atoms of oxygen
—————————————————————————————————————————–
Atomic Mass and Formula Mass
The atomic mass (AM) of an element is the average mass of all its naturally occurring isotopes, and we
can find this number on the periodic table, usually below the element’s symbol. The mass is given in the
units ‘u’. For our examples, we will round to the tenths place. We can also determine the mass of a
molecule by adding the atomic masses of its components. For example, the formula mass of sodium
chloride is the mass of one atom of sodium (23.0 u) plus the mass of one atom of chlorine (35.5 u) so the
formula mass of sodium chloride is 58.5 u.
—————————————————————————————————————————–
Example:
5. Find the formula mass (FM) of lead chromate, PbCrO4. Use the periodic table in Appendix A of this lab
Concentration
PHSC 1021 online 3 | P a g e
to look up the atomic masses of the elements.
323.2 u – Lead chromate is made up of 1 atom of Pb, 1 atom of Cr, and 4 atoms of O. The atomic
masses of those elements are: Pb (207.2 u), Cr (52.0 u), O (16.0 u)
Therefore, the formula mass of PbCrO4 is 207.2 u + 52.0 u + (4 × 16.0 u) = 323.2 u
—————————————————————————————————————————-
Concentration and Moles
Now that we know what a formula mass is, we can talk about the mole again. A mole of any substance
has a mass equal to the same number of grams as its formula mass (FM). For example, copper has a FM
of 63.5u. Therefore, a mole of Cu has a mass of 63.5 grams, and copper has a molar mass of 63.5 g/mol.
Water (H2O) has a FM of 18.0u, and a mole of H2O has a mass of 18 grams. Therefore, water has a molar
mass of 18 g/mol.
If the concentration of a solution is 1 mol/L, then there is 1 mole of the solute for every liter of solution.
Sometimes chemists need to make solutions with specific concentrations such as 2.4 mol/L or 7.6 mol/L.
To make the solution, first they find the mass of the solute needed, using the relationship between mass
and moles.
—————————————————————————————————————————–
Example:
6. What mass of PbCrO4 should be added to 1 L of water to create a solution with a concentration of 3.2
mol/L?
1034.2 grams of PbCrO4
First, find the formula mass (FM) of lead chromate, PbCrO4. It is 323.2 u (see Example 5). Remember
that the formula mass in units u is equal to the mass of 1 mole of the substance in grams. Therefore 1
mole of PbCrO4 has a mass of 323.2 grams.
Next recognize that a solution with concentration 3.2 mol/L would require 3.2 moles of the solute
added to 1 L of the water.
Then find the mass for 3.2 moles of PbCrO4. Multiply the number of moles by the molar mass of the
solute.
3.2 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4 (
323.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
1 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4
) = 1034.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
—————————————————————————————————————————-
Concentration
PHSC 1021 online 4 | P a g e
Appendix A
**## ConcentrationLabInstructions2025online-prelab.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 1: Prelab
Objectives:
• Explore concentration and saturation as related to solvents and solutes.
• Calculate molar mass and mass of solute needed for a specific concentration.
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Introduction:
A mixture is a type of matter composed of varying proportions of two or more substances that are only
physically mixed and not chemically combined. Mixtures can be divided into two categories –
heterogeneous and homogeneous. A heterogeneous mixture is non-uniform so that at least two
components can be observed examples include pizza and oil/water. A homogeneous mixture is uniform
throughout like coffee or an alloy. Another name for a liquid, homogeneous mixture is a solution. A
solution is composed of two parts 1) a solvent which is the liquid or the substance in the larger quantity,
and 2) a solute which is the substance dissolved in the solvent. Figure 1 below shows two examples of
salt-water solutions. In a salt-water solution, water is in the larger amount and is the solvent, while the
salt is in the smaller amount and is the solute. At a given temperature only a certain amount of solute can
be dissolved into the solvent. When the maximum amount of solute is present the solution is said to be
saturated. Any extra solute added to a saturated solution would remain undissolved and usually settle at
the bottom of the container. When less than the maximum amount of solute is dissolved into the solvent,
the solution is called unsaturated.
Figure 1: Two Examples of Salt-Water Solutions.
—————————————————————————————————————————–
Examples:
1. In a solution which substance is present in the larger amount, the solvent or the solute?
Solvent – The solvent is the liquid or the substance in the larger quantity
2. Take a cup of water, add sugar, and stir. If the resulting solution contains sugar crystals that do not
dissolve, is the solution saturated or unsaturated?
Unsaturated – If there is no precipitate at the bottom then it is likely less than the maximum amount of
the solute is present.
—————————————————————————————————————————–
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Moles and Molarity
In addition to the broad categories of saturated and unsaturated, solutions can be classified based on their
concentration or molarity. Molarity is the concentration of a solution expressed in the number of moles
of solute per liter of solution. In order to calculate the molarity of a solution, you need to know the
number of moles of solute and the total volume of the solution. Moles are used to measure the amount of
a substance. A mole is a number of somethings. The same way a dozen eggs means twelve eggs. A mole
of atoms is 6.02×1023 atoms. For this lab we will focus on a property of moles concerning mass. To
understand this property of moles, first we will talk about atomic mass and formula mass.
Chemical Formula and Number of Atoms
Compounds such as sodium chloride and water can be written out as words or a shorthand form of the
name can be written. This shorthand form is called the chemical formula. Look back at figure 1 and notice
that H2O is used instead of water. In the same figure NaCl is used instead of sodium chloride. The
chemical formula for a substance contains the chemical symbol for each element present. If there is more
than one atom of that element then a subscript will also be used in the chemical formula. The subscripts
show the number of atoms of that element. If there is a subscript 2, that means the compound contains two
atoms of that element. A subscript of 3 would mean the compound contains three atoms of that element.
H2O has two hydrogen atoms and one oxygen atom. NaCl has one sodium atom and one chlorine atom.
Copper(II) sulfate, CuSO4, has one copper atom, one sulfur atom, and four oxygen atoms.
The purpose of the chemical formula is to have a shorthand way of describing the compounds. Cobalt (II)
nitrate has the chemical formula Co(NO3)2. This signifies that one cobalt atom is bonded to two nitrate
ions. If we are counting atoms and parentheses are present, then we multiply the subscript times
everything in the parentheses. Therefore cobalt(II) nitrate has one cobalt atom, 2×1=2 nitrogen atoms, and
2×3=6 oxygen atoms.
—————————————————————————————————————————–
Examples:
3. The formula for potassium dichromate is K2Cr2O7. Which elements are present, and how many atoms
of each element are present in this compound?
2 K, 2 Cr, 7 O
Two atoms of potassium, two atoms of chromium, and seven atoms of oxygen
4. The formula for lead chromate is PbCrO4. Which elements are present, and how many atoms of each
element are present in this compound?
1 Pb, 1 Cr, 4 O
One atom of lead, one atom of chromium, and four atoms of oxygen
—————————————————————————————————————————–
Atomic Mass and Formula Mass
The atomic mass (AM) of an element is the average mass of all its naturally occurring isotopes, and we
can find this number on the periodic table, usually below the element’s symbol. The mass is given in the
units ‘u’. For our examples, we will round to the tenths place. We can also determine the mass of a
molecule by adding the atomic masses of its components. For example, the formula mass of sodium
chloride is the mass of one atom of sodium (23.0 u) plus the mass of one atom of chlorine (35.5 u) so the
formula mass of sodium chloride is 58.5 u.
—————————————————————————————————————————–
Example:
5. Find the formula mass (FM) of lead chromate, PbCrO4. Use the periodic table in Appendix A of this lab
Concentration
PHSC 1021 online 3 | P a g e
to look up the atomic masses of the elements.
323.2 u – Lead chromate is made up of 1 atom of Pb, 1 atom of Cr, and 4 atoms of O. The atomic
masses of those elements are: Pb (207.2 u), Cr (52.0 u), O (16.0 u)
Therefore, the formula mass of PbCrO4 is 207.2 u + 52.0 u + (4 × 16.0 u) = 323.2 u
—————————————————————————————————————————-
Concentration and Moles
Now that we know what a formula mass is, we can talk about the mole again. A mole of any substance
has a mass equal to the same number of grams as its formula mass (FM). For example, copper has a FM
of 63.5u. Therefore, a mole of Cu has a mass of 63.5 grams, and copper has a molar mass of 63.5 g/mol.
Water (H2O) has a FM of 18.0u, and a mole of H2O has a mass of 18 grams. Therefore, water has a molar
mass of 18 g/mol.
If the concentration of a solution is 1 mol/L, then there is 1 mole of the solute for every liter of solution.
Sometimes chemists need to make solutions with specific concentrations such as 2.4 mol/L or 7.6 mol/L.
To make the solution, first they find the mass of the solute needed, using the relationship between mass
and moles.
—————————————————————————————————————————–
Example:
6. What mass of PbCrO4 should be added to 1 L of water to create a solution with a concentration of 3.2
mol/L?
1034.2 grams of PbCrO4
First, find the formula mass (FM) of lead chromate, PbCrO4. It is 323.2 u (see Example 5). Remember
that the formula mass in units u is equal to the mass of 1 mole of the substance in grams. Therefore 1
mole of PbCrO4 has a mass of 323.2 grams.
Next recognize that a solution with concentration 3.2 mol/L would require 3.2 moles of the solute
added to 1 L of the water.
Then find the mass for 3.2 moles of PbCrO4. Multiply the number of moles by the molar mass of the
solute.
3.2 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4 (
323.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
1 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4
) = 1034.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
—————————————————————————————————————————-
Concentration
PHSC 1021 online 4 | P a g e
Appendix A
**## ConcentrationLabInstructions2025online-activities.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 2: Activities
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Activity 1: Molar Mass Calculations
For this activity, you will need the periodic table in Appendix A of the prelab.
Using the periodic table, determine the molar mass of the following compounds:
1. Cobalt(II) nitrate, Co(NO3)2
2. Cobalt(II) chloride, CoCl2
3. Potassium dichromate, K2Cr2O7
4. Potassium chromate, K2CrO4
5. Nickel(II) chloride, NiCl2
6. Copper(II) sulfate, CuSO4
7. Potassium permanganate, KMnO4
8. Sodium chloride, NaCl
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Activity 2: Saturated Solutions
For this activity, you will be using the Concentration simulation on the PhET website. The web address
for this simulation is given at the beginning of the lab handout under Web Links. You can also click here
to take you to the simulation. You are going to investigate the effect of varying the amount of solute,
solvent, and solution on the saturation of the solution.
1. Open the PhET Concentration Simulation.
2. Move the crosshairs end of the concentration meter into the solution. It will read 0.000 mol/L. Leave
the solute selection dropdown menu set to “Drink Mix”.Shake the solute shaker a few times. This will
add drink mix to the water. Notice the change in the concentration. In table 1, in the “Drink mix is
added” describe what happens to the concentration, e.g. remains the same, increases, decreases, goes
to zero.
3. Then add additional water to the solution. In table 1 column 3, describe what happens to the
concentration, e.g. remains the same, increases, decreases, goes to zero.
4. Adjust the evaporation slider, so that it is no longer set to “none”. Describe the effect on the
concentration of the solution in table 1 column 4.
5. Drain some (not all) of the solution and describe the effect on the concentration of the solution in table
1 column 5.
6. Click on the “Remove Solute” button and describe the effect on the concentration of the solution in
table 1 column 6.
Figure 1: PhET Concentration Simulation. The arrows point to the pieces that move and affect the concentration and or
amount of solution. The solute can be changed using the drop-down menu at the top right.
[https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html](https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html)
PHSC 1021 online 3 | P a g e
Table 1: Effect of Various Actions on the Concentration of a Solution
Action
Drink mix is
added
Water is added
Evaporation
occurs
Solution is drained
Solute is removed
What happens to
concentration?
7. Reset the simulation and insert the concentration meter into the solution.
8. Keep the solute to “Drink mix” and add as much as you can.
9. How do you know when a solution is saturated?
10. While the solution is saturated, add additional solid solute. What happens?
11. Why do you think this is?
12. How does adding this additional solute change the concentration of the saturated solution?
13. Increase the evaporation of the saturated solution. How does evaporation change the concentration of
the saturated solution?
Concentration
PHSC 1021 online 4 | P a g e
Activity 3: Solute Mass of Saturated Solutions
For this activity, you will continue using the Concentration simulation on the PhET website. You are
going to use the simulation to determine the saturation concentration of different solutes dissolved in
water. Then you will calculate the mass of the solute in the saturated solutions.
1. Reset the Concentration Simulation.
2. Fill the beaker to 1 L.
3. Keep the evaporation set to “none”, and place the concentration sensor in the solution.
4. For each solute in table 2, find and record the concentration when saturation occurs. (You can do this
by shaking the solute shaker until the word “saturated” appears. Then read the concentration on the
sensor.) Complete the second column of table 2 with your results.
Table 2: Concentration and Solute Mass for Various Solutes
Solute Concentration for
Saturation
(mol/L)
Solute Mass
(grams)
Drink mix
Cobalt (II) nitrate
Cobalt (II) chloride
Potassium dichromate
Potassium chromate
Nickel (II) chloride
Copper (II) sulfate
Potassium permanganate
Sodium chloride
5. Does each solute have the same concentration at saturation?
6. For each solute, determine the mass in grams required to saturate 1 L of solution. Record these
values in column 3 of the table 2. See example 6 in the prelab for a reminder of how to determine the
mass of a one liter saturated solution.
References
1. This lab was adapted from an activity provided by: University of Colorado. (). PhET Interactive
Simulations – Physics, PhET: Interactive simulations. Retrieved at May 7, 2020, from the website
https://phet.colorado.edu/en/contributions/view/4280
[https://phet.colorado.edu/en/contributions/view/4280](https://phet.colorado.edu/en/contributions/view/4280)
**## ConcentrationLabInstructions2025online-prelab.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 1: Prelab
Objectives:
• Explore concentration and saturation as related to solvents and solutes.
• Calculate molar mass and mass of solute needed for a specific concentration.
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Introduction:
A mixture is a type of matter composed of varying proportions of two or more substances that are only
physically mixed and not chemically combined. Mixtures can be divided into two categories –
heterogeneous and homogeneous. A heterogeneous mixture is non-uniform so that at least two
components can be observed examples include pizza and oil/water. A homogeneous mixture is uniform
throughout like coffee or an alloy. Another name for a liquid, homogeneous mixture is a solution. A
solution is composed of two parts 1) a solvent which is the liquid or the substance in the larger quantity,
and 2) a solute which is the substance dissolved in the solvent. Figure 1 below shows two examples of
salt-water solutions. In a salt-water solution, water is in the larger amount and is the solvent, while the
salt is in the smaller amount and is the solute. At a given temperature only a certain amount of solute can
be dissolved into the solvent. When the maximum amount of solute is present the solution is said to be
saturated. Any extra solute added to a saturated solution would remain undissolved and usually settle at
the bottom of the container. When less than the maximum amount of solute is dissolved into the solvent,
the solution is called unsaturated.
Figure 1: Two Examples of Salt-Water Solutions.
—————————————————————————————————————————–
Examples:
1. In a solution which substance is present in the larger amount, the solvent or the solute?
Solvent – The solvent is the liquid or the substance in the larger quantity
2. Take a cup of water, add sugar, and stir. If the resulting solution contains sugar crystals that do not
dissolve, is the solution saturated or unsaturated?
Unsaturated – If there is no precipitate at the bottom then it is likely less than the maximum amount of
the solute is present.
—————————————————————————————————————————–
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Moles and Molarity
In addition to the broad categories of saturated and unsaturated, solutions can be classified based on their
concentration or molarity. Molarity is the concentration of a solution expressed in the number of moles
of solute per liter of solution. In order to calculate the molarity of a solution, you need to know the
number of moles of solute and the total volume of the solution. Moles are used to measure the amount of
a substance. A mole is a number of somethings. The same way a dozen eggs means twelve eggs. A mole
of atoms is 6.02×1023 atoms. For this lab we will focus on a property of moles concerning mass. To
understand this property of moles, first we will talk about atomic mass and formula mass.
Chemical Formula and Number of Atoms
Compounds such as sodium chloride and water can be written out as words or a shorthand form of the
name can be written. This shorthand form is called the chemical formula. Look back at figure 1 and notice
that H2O is used instead of water. In the same figure NaCl is used instead of sodium chloride. The
chemical formula for a substance contains the chemical symbol for each element present. If there is more
than one atom of that element then a subscript will also be used in the chemical formula. The subscripts
show the number of atoms of that element. If there is a subscript 2, that means the compound contains two
atoms of that element. A subscript of 3 would mean the compound contains three atoms of that element.
H2O has two hydrogen atoms and one oxygen atom. NaCl has one sodium atom and one chlorine atom.
Copper(II) sulfate, CuSO4, has one copper atom, one sulfur atom, and four oxygen atoms.
The purpose of the chemical formula is to have a shorthand way of describing the compounds. Cobalt (II)
nitrate has the chemical formula Co(NO3)2. This signifies that one cobalt atom is bonded to two nitrate
ions. If we are counting atoms and parentheses are present, then we multiply the subscript times
everything in the parentheses. Therefore cobalt(II) nitrate has one cobalt atom, 2×1=2 nitrogen atoms, and
2×3=6 oxygen atoms.
—————————————————————————————————————————–
Examples:
3. The formula for potassium dichromate is K2Cr2O7. Which elements are present, and how many atoms
of each element are present in this compound?
2 K, 2 Cr, 7 O
Two atoms of potassium, two atoms of chromium, and seven atoms of oxygen
4. The formula for lead chromate is PbCrO4. Which elements are present, and how many atoms of each
element are present in this compound?
1 Pb, 1 Cr, 4 O
One atom of lead, one atom of chromium, and four atoms of oxygen
—————————————————————————————————————————–
Atomic Mass and Formula Mass
The atomic mass (AM) of an element is the average mass of all its naturally occurring isotopes, and we
can find this number on the periodic table, usually below the element’s symbol. The mass is given in the
units ‘u’. For our examples, we will round to the tenths place. We can also determine the mass of a
molecule by adding the atomic masses of its components. For example, the formula mass of sodium
chloride is the mass of one atom of sodium (23.0 u) plus the mass of one atom of chlorine (35.5 u) so the
formula mass of sodium chloride is 58.5 u.
—————————————————————————————————————————–
Example:
5. Find the formula mass (FM) of lead chromate, PbCrO4. Use the periodic table in Appendix A of this lab
Concentration
PHSC 1021 online 3 | P a g e
to look up the atomic masses of the elements.
323.2 u – Lead chromate is made up of 1 atom of Pb, 1 atom of Cr, and 4 atoms of O. The atomic
masses of those elements are: Pb (207.2 u), Cr (52.0 u), O (16.0 u)
Therefore, the formula mass of PbCrO4 is 207.2 u + 52.0 u + (4 × 16.0 u) = 323.2 u
—————————————————————————————————————————-
Concentration and Moles
Now that we know what a formula mass is, we can talk about the mole again. A mole of any substance
has a mass equal to the same number of grams as its formula mass (FM). For example, copper has a FM
of 63.5u. Therefore, a mole of Cu has a mass of 63.5 grams, and copper has a molar mass of 63.5 g/mol.
Water (H2O) has a FM of 18.0u, and a mole of H2O has a mass of 18 grams. Therefore, water has a molar
mass of 18 g/mol.
If the concentration of a solution is 1 mol/L, then there is 1 mole of the solute for every liter of solution.
Sometimes chemists need to make solutions with specific concentrations such as 2.4 mol/L or 7.6 mol/L.
To make the solution, first they find the mass of the solute needed, using the relationship between mass
and moles.
—————————————————————————————————————————–
Example:
6. What mass of PbCrO4 should be added to 1 L of water to create a solution with a concentration of 3.2
mol/L?
1034.2 grams of PbCrO4
First, find the formula mass (FM) of lead chromate, PbCrO4. It is 323.2 u (see Example 5). Remember
that the formula mass in units u is equal to the mass of 1 mole of the substance in grams. Therefore 1
mole of PbCrO4 has a mass of 323.2 grams.
Next recognize that a solution with concentration 3.2 mol/L would require 3.2 moles of the solute
added to 1 L of the water.
Then find the mass for 3.2 moles of PbCrO4. Multiply the number of moles by the molar mass of the
solute.
3.2 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4 (
323.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
1 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4
) = 1034.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
—————————————————————————————————————————-
Concentration
PHSC 1021 online 4 | P a g e
Appendix A
**## ConcentrationLabInstructions2025online-activities.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 2: Activities
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Activity 1: Molar Mass Calculations
For this activity, you will need the periodic table in Appendix A of the prelab.
Using the periodic table, determine the molar mass of the following compounds:
1. Cobalt(II) nitrate, Co(NO3)2
2. Cobalt(II) chloride, CoCl2
3. Potassium dichromate, K2Cr2O7
4. Potassium chromate, K2CrO4
5. Nickel(II) chloride, NiCl2
6. Copper(II) sulfate, CuSO4
7. Potassium permanganate, KMnO4
8. Sodium chloride, NaCl
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Activity 2: Saturated Solutions
For this activity, you will be using the Concentration simulation on the PhET website. The web address
for this simulation is given at the beginning of the lab handout under Web Links. You can also click here
to take you to the simulation. You are going to investigate the effect of varying the amount of solute,
solvent, and solution on the saturation of the solution.
1. Open the PhET Concentration Simulation.
2. Move the crosshairs end of the concentration meter into the solution. It will read 0.000 mol/L. Leave
the solute selection dropdown menu set to “Drink Mix”.Shake the solute shaker a few times. This will
add drink mix to the water. Notice the change in the concentration. In table 1, in the “Drink mix is
added” describe what happens to the concentration, e.g. remains the same, increases, decreases, goes
to zero.
3. Then add additional water to the solution. In table 1 column 3, describe what happens to the
concentration, e.g. remains the same, increases, decreases, goes to zero.
4. Adjust the evaporation slider, so that it is no longer set to “none”. Describe the effect on the
concentration of the solution in table 1 column 4.
5. Drain some (not all) of the solution and describe the effect on the concentration of the solution in table
1 column 5.
6. Click on the “Remove Solute” button and describe the effect on the concentration of the solution in
table 1 column 6.
Figure 1: PhET Concentration Simulation. The arrows point to the pieces that move and affect the concentration and or
amount of solution. The solute can be changed using the drop-down menu at the top right.
[https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html](https://phet.colorado.edu/sims/html/concentration/latest/concentration_all.html)
PHSC 1021 online 3 | P a g e
Table 1: Effect of Various Actions on the Concentration of a Solution
Action
Drink mix is
added
Water is added
Evaporation
occurs
Solution is drained
Solute is removed
What happens to
concentration?
7. Reset the simulation and insert the concentration meter into the solution.
8. Keep the solute to “Drink mix” and add as much as you can.
9. How do you know when a solution is saturated?
10. While the solution is saturated, add additional solid solute. What happens?
11. Why do you think this is?
12. How does adding this additional solute change the concentration of the saturated solution?
13. Increase the evaporation of the saturated solution. How does evaporation change the concentration of
the saturated solution?
Concentration
PHSC 1021 online 4 | P a g e
Activity 3: Solute Mass of Saturated Solutions
For this activity, you will continue using the Concentration simulation on the PhET website. You are
going to use the simulation to determine the saturation concentration of different solutes dissolved in
water. Then you will calculate the mass of the solute in the saturated solutions.
1. Reset the Concentration Simulation.
2. Fill the beaker to 1 L.
3. Keep the evaporation set to “none”, and place the concentration sensor in the solution.
4. For each solute in table 2, find and record the concentration when saturation occurs. (You can do this
by shaking the solute shaker until the word “saturated” appears. Then read the concentration on the
sensor.) Complete the second column of table 2 with your results.
Table 2: Concentration and Solute Mass for Various Solutes
Solute Concentration for
Saturation
(mol/L)
Solute Mass
(grams)
Drink mix
Cobalt (II) nitrate
Cobalt (II) chloride
Potassium dichromate
Potassium chromate
Nickel (II) chloride
Copper (II) sulfate
Potassium permanganate
Sodium chloride
5. Does each solute have the same concentration at saturation?
6. For each solute, determine the mass in grams required to saturate 1 L of solution. Record these
values in column 3 of the table 2. See example 6 in the prelab for a reminder of how to determine the
mass of a one liter saturated solution.
References
1. This lab was adapted from an activity provided by: University of Colorado. (). PhET Interactive
Simulations – Physics, PhET: Interactive simulations. Retrieved at May 7, 2020, from the website
https://phet.colorado.edu/en/contributions/view/4280
[https://phet.colorado.edu/en/contributions/view/4280](https://phet.colorado.edu/en/contributions/view/4280)
**## ConcentrationLabInstructions2025online-prelab.pdf**
PHSC 1021 online 1 | P a g e
Concentration part 1: Prelab
Objectives:
• Explore concentration and saturation as related to solvents and solutes.
• Calculate molar mass and mass of solute needed for a specific concentration.
Web link:
• PhET Concentration https://phet.colorado.edu/en/simulations/concentration
Introduction:
A mixture is a type of matter composed of varying proportions of two or more substances that are only
physically mixed and not chemically combined. Mixtures can be divided into two categories –
heterogeneous and homogeneous. A heterogeneous mixture is non-uniform so that at least two
components can be observed examples include pizza and oil/water. A homogeneous mixture is uniform
throughout like coffee or an alloy. Another name for a liquid, homogeneous mixture is a solution. A
solution is composed of two parts 1) a solvent which is the liquid or the substance in the larger quantity,
and 2) a solute which is the substance dissolved in the solvent. Figure 1 below shows two examples of
salt-water solutions. In a salt-water solution, water is in the larger amount and is the solvent, while the
salt is in the smaller amount and is the solute. At a given temperature only a certain amount of solute can
be dissolved into the solvent. When the maximum amount of solute is present the solution is said to be
saturated. Any extra solute added to a saturated solution would remain undissolved and usually settle at
the bottom of the container. When less than the maximum amount of solute is dissolved into the solvent,
the solution is called unsaturated.
Figure 1: Two Examples of Salt-Water Solutions.
—————————————————————————————————————————–
Examples:
1. In a solution which substance is present in the larger amount, the solvent or the solute?
Solvent – The solvent is the liquid or the substance in the larger quantity
2. Take a cup of water, add sugar, and stir. If the resulting solution contains sugar crystals that do not
dissolve, is the solution saturated or unsaturated?
Unsaturated – If there is no precipitate at the bottom then it is likely less than the maximum amount of
the solute is present.
—————————————————————————————————————————–
[https://phet.colorado.edu/en/simulations/concentration](https://phet.colorado.edu/en/simulations/concentration)
Concentration
PHSC 1021 online 2 | P a g e
Moles and Molarity
In addition to the broad categories of saturated and unsaturated, solutions can be classified based on their
concentration or molarity. Molarity is the concentration of a solution expressed in the number of moles
of solute per liter of solution. In order to calculate the molarity of a solution, you need to know the
number of moles of solute and the total volume of the solution. Moles are used to measure the amount of
a substance. A mole is a number of somethings. The same way a dozen eggs means twelve eggs. A mole
of atoms is 6.02×1023 atoms. For this lab we will focus on a property of moles concerning mass. To
understand this property of moles, first we will talk about atomic mass and formula mass.
Chemical Formula and Number of Atoms
Compounds such as sodium chloride and water can be written out as words or a shorthand form of the
name can be written. This shorthand form is called the chemical formula. Look back at figure 1 and notice
that H2O is used instead of water. In the same figure NaCl is used instead of sodium chloride. The
chemical formula for a substance contains the chemical symbol for each element present. If there is more
than one atom of that element then a subscript will also be used in the chemical formula. The subscripts
show the number of atoms of that element. If there is a subscript 2, that means the compound contains two
atoms of that element. A subscript of 3 would mean the compound contains three atoms of that element.
H2O has two hydrogen atoms and one oxygen atom. NaCl has one sodium atom and one chlorine atom.
Copper(II) sulfate, CuSO4, has one copper atom, one sulfur atom, and four oxygen atoms.
The purpose of the chemical formula is to have a shorthand way of describing the compounds. Cobalt (II)
nitrate has the chemical formula Co(NO3)2. This signifies that one cobalt atom is bonded to two nitrate
ions. If we are counting atoms and parentheses are present, then we multiply the subscript times
everything in the parentheses. Therefore cobalt(II) nitrate has one cobalt atom, 2×1=2 nitrogen atoms, and
2×3=6 oxygen atoms.
—————————————————————————————————————————–
Examples:
3. The formula for potassium dichromate is K2Cr2O7. Which elements are present, and how many atoms
of each element are present in this compound?
2 K, 2 Cr, 7 O
Two atoms of potassium, two atoms of chromium, and seven atoms of oxygen
4. The formula for lead chromate is PbCrO4. Which elements are present, and how many atoms of each
element are present in this compound?
1 Pb, 1 Cr, 4 O
One atom of lead, one atom of chromium, and four atoms of oxygen
—————————————————————————————————————————–
Atomic Mass and Formula Mass
The atomic mass (AM) of an element is the average mass of all its naturally occurring isotopes, and we
can find this number on the periodic table, usually below the element’s symbol. The mass is given in the
units ‘u’. For our examples, we will round to the tenths place. We can also determine the mass of a
molecule by adding the atomic masses of its components. For example, the formula mass of sodium
chloride is the mass of one atom of sodium (23.0 u) plus the mass of one atom of chlorine (35.5 u) so the
formula mass of sodium chloride is 58.5 u.
—————————————————————————————————————————–
Example:
5. Find the formula mass (FM) of lead chromate, PbCrO4. Use the periodic table in Appendix A of this lab
Concentration
PHSC 1021 online 3 | P a g e
to look up the atomic masses of the elements.
323.2 u – Lead chromate is made up of 1 atom of Pb, 1 atom of Cr, and 4 atoms of O. The atomic
masses of those elements are: Pb (207.2 u), Cr (52.0 u), O (16.0 u)
Therefore, the formula mass of PbCrO4 is 207.2 u + 52.0 u + (4 × 16.0 u) = 323.2 u
—————————————————————————————————————————-
Concentration and Moles
Now that we know what a formula mass is, we can talk about the mole again. A mole of any substance
has a mass equal to the same number of grams as its formula mass (FM). For example, copper has a FM
of 63.5u. Therefore, a mole of Cu has a mass of 63.5 grams, and copper has a molar mass of 63.5 g/mol.
Water (H2O) has a FM of 18.0u, and a mole of H2O has a mass of 18 grams. Therefore, water has a molar
mass of 18 g/mol.
If the concentration of a solution is 1 mol/L, then there is 1 mole of the solute for every liter of solution.
Sometimes chemists need to make solutions with specific concentrations such as 2.4 mol/L or 7.6 mol/L.
To make the solution, first they find the mass of the solute needed, using the relationship between mass
and moles.
—————————————————————————————————————————–
Example:
6. What mass of PbCrO4 should be added to 1 L of water to create a solution with a concentration of 3.2
mol/L?
1034.2 grams of PbCrO4
First, find the formula mass (FM) of lead chromate, PbCrO4. It is 323.2 u (see Example 5). Remember
that the formula mass in units u is equal to the mass of 1 mole of the substance in grams. Therefore 1
mole of PbCrO4 has a mass of 323.2 grams.
Next recognize that a solution with concentration 3.2 mol/L would require 3.2 moles of the solute
added to 1 L of the water.
Then find the mass for 3.2 moles of PbCrO4. Multiply the number of moles by the molar mass of the
solute.
3.2 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4 (
323.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
1 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑃𝑏𝐶𝑟𝑂4
) = 1034.2 𝑔 𝑃𝑏𝐶𝑟𝑂4
—————————————————————————————————————————-
Concentration
PHSC 1021 online 4 | P a g e
Appendix A
– 1
– 2