Task 1
Changing the Amount of Ammonia
In this task, you will carry out the chemical reaction between ammonia and Epsom salt:
2NH3 + MgSO4 + 2H2O → Mg(OH)2 + (NH4)2SO4.
You’ll use varying amounts of ammonia to see how the amount of a reactant affects the amount of product.
You’ll need these materials:
safety goggles
protective gloves
apron
3 identical empty disposable water bottles, about 16.9 fluid ounces each
permanent marker
water
Epsom salt (3 tablespoons)
tablespoon measure
-cup measure
ammonia (1 to 2 cups)
To begin the experiment, follow these steps. Use this diagram to help you work through the steps:
Label the three bottles with the numbers 1 through 3 using the permanent marker.
Add 1 tablespoon of Epsom salt to each bottle.
Add the following amounts of water to each bottle:
bottle 1: cup
bottle 2: cup + 1 tablespoon
bottle 3: 1 tablespoon
The amounts are different so that the total volume of liquid in each bottle will be the same after the ammonia is added.
Add the following amounts of ammonia to each bottle:
bottle 1: 1 tablespoon
bottle 2: cup
bottle 3: cup
Cap each bottle tightly.
Rinse the outsides of the bottles to remove any ammonia that may have spilled onto them.
Swirl the bottles to dissolve the Epsom salt.
Let the bottles sit overnight, or for at least 8 hours.
If solids end up floating on the surfaces of the solutions, tap or gently shake the bottles until the solids sink to the bottom. Wait several minutes for the solids to collect at the bottom of the bottles.
Part A
Look at the three bottles. What evidence is there that a chemical reaction took place?
Part B
Compare bottles 1 and 2. How do the amounts of the reactants compare? How do the amounts of the products compare? For these two bottles, does the amount of product appear to be proportional to the amount of ammonia used?
Part C
Compare bottles 2 and 3. How do the amounts of the reactants compare? How do the amounts of the products compare? For these two bottles, does the amount of product appear to be proportional to the amount of ammonia used?
Part D
Compare your answers in parts B and C. If your answers to those questions are different, explain why they’re different.
Part E
Imagine mixing 1 tablespoon of Epsom salt with 2 cups of ammonia. How much precipitate would be produced? Describe the amount of precipitate by comparing it with the amount in bottle 1, 2, or 3. Explain your prediction.
Task 2
Changing the Amount of Epsom Salt
In this task, you will carry out the chemical reaction between Epsom salt and ammonia:
2NH3 + MgSO4 + 2H2O → Mg(OH)2 + (NH4)2SO4.
This time, you’ll use varying amounts of Epsom salt to see how the amount of a reactant affects the amount of product.
You’ll need these materials:
safety goggles
protective gloves
apron
3 identical empty disposable water bottles, about 16.9 fluid ounces each
permanent marker
Epsom salt (8.5 tablespoons)
tablespoon measure and -tablespoon measure (or a -teaspoon measure; note that teaspoons equals tablespoon)
-cup measure
water
ammonia (1 cup)
To begin the experiment, follow these steps. Use this diagram to help you work through the steps:
Label the three bottles with the numbers 1 through 3 using the permanent marker.
Add the following amounts of Epsom salt to each bottle.
bottle 1: tablespoon
bottle 2: 2 tablespoons
bottle 3: 6 tablespoons
Add cup of water to each bottle.
Add cup of ammonia to each bottle.
Cap each bottle tightly.
Rinse the outsides of the bottles to remove any ammonia that may have spilled onto them.
Swirl the bottles to dissolve the Epsom salt.
Let the bottles sit overnight, or for at least 8 hours.
If solids end up floating on the surfaces of the solutions, tap or gently shake the bottles until the solids sink to the bottom. Wait several minutes for the solids to collect at the bottom of the bottles.
Part A
Compare bottles 1 and 2. How do the amounts of the reactants compare? How do the amounts of the products compare? For these two bottles, does the amount of product appear to be proportional to the amount of Epsom salt used?
Part B
Compare bottles 2 and 3. How do the amounts of the reactants compare? How do the amounts of the products compare? For these two bottles, does the amount of product appear to be proportional to the amount of Epsom salt used?
Part C
Compare your answers from parts A and B. If your answers to those questions are different, explain why they’re different.
Part D
Imagine mixing 10 tablespoons of Epsom salt with cup of ammonia. How much precipitate would be produced? Describe the amount of precipitate by comparing it with the amount in bottle 1, 2, or 3. Explain your prediction.
Part E
In task 1, you varied the amount of ammonia used in the reaction. In task 2, you varied the amount of Epsom salt. Combining the results of these two tasks, what can you conclude about the amount of product formed by two reactants?