Calculations Involving Phase Changes Answer Key (CHEM 1405)

Back to Chemistry 1405 Practice Problems

1)  A 12 oz. can of soda weighs about 450 grams.  How many kilojoules are released when a can of soda is cooled from 25 degrees Celsius (room temperature) to 4 degrees Celsius (the temperature of a refrigerator). Assume the can of soda has approximately the same specific heat as pure water.  The specific heat of liquid water is 4.184 J/g˚C.

 

 

2)  How many kilojoules are required to heat 250 grams of liquid water from 0^oC to 100^oC ?

 

 

3)  How many kilojoules are required to melt 100 grams of water? The heat of fusion of water is 334 J/g.

 

 

4)  How many kilojoules are required to boil 150 grams of water? The heat of vaporization of water is 2260 J/g.

 

 

5)  How many kilojoules are required to heat 200 grams of water from 25^oC to 125^oC? The specific heat of steam is 1.84 J / g ^oC.

 

 

6)  How many kilojoules are given off when 120 grams of water are cooled from 25^oC to -25^oC? The specific heat of ice is 2.09 J / g^oC.

 

 

7)  How many kilojoules are required to heat 75 grams of water from -85^oC to 185^oC? The specific heat of steam is 1.84 J / g^oC.

 

 

8)  How many kilojoules are required to heat a frozen can of juice (360 grams) from -5^oC (the temperature of an overcooled refrigerator) to 110^oC (the highest practical temperature within a microwave oven)?  Assume the heat of fusion, the heat of vaporization, and the specific heats of solid, liquid, and gas juice are roughly the same as that of pure water.

 

 

9)  How many joules are released when 450 grams of water are cooled from 4 x 10^7oC (the hottest temperature ever achieved by man) to 1 x 10^-9oC (the coldest temperature achieved by man).

 

 

10)  How many joules are required to raise the temperature of 100 grams of water from -269^oC (the current temperature of space) to 1.6 x 10^15oC (the estimated temperature of space immediately after the big bang)?