Chapter 16: Test Review 2008 answers

 

  1. How much heat energy is required to vaporize 1 gram of water? 1 mole of water?

 

1 gram * 1 mole/18 g * 40.7 kJ/mole = 2.26 kJ

 

1 mole * 40.7 kJ/mole = 40.7 kJ

 

 

  1. How much heat energy is required to melt 1 gram of water? 1 mole of water?

                       

1 gram * 1 mole/18 g * 6.01 kJ/mole = 0.333 kJ

1 mole * 6.01 kJ/mole = 6.01 kJ

 

  1. How much heat energy is required to change the temperature of …
    1. 1 gram of liquid water from 0 degrees Celsius to 100 degrees Celsius?

 

418.4 J

 

    1. 1 mole water from 0 degrees Celsius to 100 degrees Celsius?

 

7531.2 J

 

  1. A 50 gram sample of ice starts at 0 degrees Celsius.  The ice is melted, warmed to 100 degrees Celsius then vaporized to create 50 grams of gaseous water (steam) at 100 degrees Celsius.
    1. Calculate the total amount of heat energy required.  Express your answer in joules, kJ and calories.

Melt = 16.69 kJ

Warm = 20.9 kJ

Vaporize = 113 kJ

Total = 150.59 kJ = 150,590 J = 35,992 calories       

 

 

  1. A 50 gram sample of steam at 100 degrees Celsius is cooled until it becomes a 50 gram sample of ice at degrees Celsius.  How much heat energy was removed from the water to accomplish this?

 

 

                        Same as #4

 

 

 

 

 

 

  1. For the reaction below: 
    1. Calculate the ΔH
    2. Draw an enthalpy diagram
    3. Determine whether the reaction is endothermic or exothermic
    4. Is heat released into the surroundings or absorbed by the surroundings?
    5. If the reaction takes place in a calorimeter filled with water would you expect the water temperature to increase or decrease?

 

         Reaction:   Sn + 2Cl2 à SnCl4

 

Given the following information:

 

Sn + Cl2 à SnCl2   ΔH = -325 kJ

 

SnCl2 + Cl2 à SnCl4 ΔH= -186 kJ

 

a.       delta H = -511 kJ

b.      products on bottom line and reactants on top line

c.       exothermic

d.      released

e.       increase

 

  1. Convert the following:
    1. 390 joules to calories

           93 calories

    1. 234 calories to kJ

                                   0.978 kJ

 

  1. Equal amounts of heat energy are transferred to two samples. The masses of the two samples are the same. Sample A has a heat capacity of 0.56 J/gC and sample B has a heat capacity of 2.45 J/gC. 
    1. Compare the change in temperature of the two samples. 
    2. Sample A and Sample B are both placed in boiling water. Each sample is then removed and placed in separate cups of water at 25 degrees Celsius. Compare the temperature increases in each cup of water.

 

Sample B has a higher heat capacity therefore it will take more heat energy to change its temperature and it will give off more heat energy when it cools down.

 

a. Sample A will experience a greater temperature increase because it takes less heat energy to change its temperature

b. The cup of water with sample B added will experience a greater increase in temperature because sample B will release more heat energy for the given change in temperature.