A saturated solution of KNO3 is prepared at 70°C using 100 grams of water. If the solution is cooled to 40°C, how many grams of KNO3 will recrystallize?

A. 30 grams
Incorrect. At 70°C, 130 grams of KNO3 is dissolved. At 40°C, 60 grams of KNO3 is dissolved. Subtract 130 grams from 40 grams to find out the amount of KNO3 that will crystallize out.

B. 55 grams
Incorrect. At 70°C, 130 grams of KNO3 is dissolved. At 40°C, 60 grams of KNO3 is dissolved. Subtract 130 grams from 40 grams to find out the amount of KNO3 that will crystallize out.

C. 60 grams
Incorrect. At 70°C, 130 grams of KNO3 is dissolved. At 40°C, 60 grams of KNO3 is dissolved. Subtract 130 grams from 40 grams to find out the amount of KNO3 that will crystallize out.

D. 70 grams
Correct!

A student needs to fully dissolve 30 grams of KClO3 in 100 grams of H2O. What is the lowest possible temperature the solution can be heated to fully dissolve all of this solute?

A. 10°C
Incorrect. Find 30 grams on the y-axis and follow it until it intersects with the KClO3 line. Then follow that point down to the x-axis to determine what temperature the solution needs to dissolve exactly 30 grams of KClO3.

B. 35°C
Incorrect. Find 30 grams on the y-axis and follow it until it intersects with the KClO3 line. Then follow that point down to the x-axis to determine what temperature the solution needs to dissolve exactly 30 grams of KClO3.

C. 55°C
Incorrect. Find 30 grams on the y-axis and follow it until it intersects with the KClO3 line. Then follow that point down to the x-axis to determine what temperature the solution needs to dissolve exactly 30 grams of KClO3.

D. 70°C
Correct!

How many grams of K2Cr2O7 are required to be added to 100 grams of H2O to make a saturated solution at 50°C?

A. 80 grams
Incorrect. Find 50°C on the x-axis and follow it up until it intersects with the line for K2Cr2O7. Then follow over to the y-axis to see the amount that can be dissolved at 50°C.

B. 65 grams
Incorrect. Find 50°C on the x-axis and follow it up until it intersects with the line for K2Cr2O7. Then follow over to the y-axis to see the amount that can be dissolved at 50°C.

C. 50 grams
Incorrect. Find 50°C on the x-axis and follow it up until it intersects with the line for K2Cr2O7. Then follow over to the y-axis to see the amount that can be dissolved at 50°C.

D. 30 grams
Correct!

Fifty-five grams of NaNO3 are dissolved in 100 grams of H2O at 30°C. When 5 grams more of NaNO3 is added to the solution, what will happen?

A. It will dissolve because it is an unsaturated solution.
Correct!

B. It will dissolve because it is a supersaturated solution.
Incorrect. At 30°C, NaNO3 can dissolve about 95 grams. The question asks, 55 grams + 5 grams = 60 grams. The total amount is still below 95 grams, so this is an unsaturated solution where all solute will fully dissolve.

C. It will not dissolve because it is a saturated solution.
Incorrect. At 30°C, NaNO3 can dissolve about 95 grams. The question asks, 55 grams + 5 grams = 60 grams. The total amount is still below 95 grams, so this is an unsaturated solution where all solute will fully dissolve.

D. Not enough information is given to determine what will happen.
Incorrect. At 30°C, NaNO3 can dissolve about 95 grams. The question asks, 55 grams + 5 grams = 60 grams. The total amount is still below 95 grams, so this is an unsaturated solution where all solute will fully dissolve.