Chemistry Test: Heat
Multiple Choice : (4 Points each)
1.
In an endothermic reaction, the energy of the reactants is ______ the energy of the products.
a. less than
b. the same as
c. more than
2. When ammonium hydroxide is added to water, the test tube feels cold to your
hand. This is an example of ______________ reaction.
a. an exothermic
b. an endothermic
c. a chemical
d. a neutral
3.
In an exothermic reaction the products store ____________the reactants.
a. the same amount of energy as
b. less energy than
c. more energy than
4. In an endothermic reaction, the energy term is on the _________ side of the
equation.
a. reactant
b. product
c. positive
5. In an exothermic reaction, H will be a __________ value.
a. positive
b. negative
c. neutral
6. The amount of heat required to raise the temperature of one gram sample by
1oC is:
a. heat capacity
b. heat of fusion
c. molar heat
d. specific heat
7.
What happens to H if a chemical equation is reversed ?
a. It becomes zero.
b. It remains the same.
c. depends on the reaction.
d. It changes sign.
8.
The enthalpy change for melting a solid, such as ice, is called
a. heat of fusion.
b. heat of vaporization.
c. specific heat.
d. heat capacity.
9.
Which of the following statements about bonds and energy is correct?
a. Bond breaking and bond formation both requires energy.
b. Bond formation requires energy and bond breaking releases energy.
c. Bond breaking requires energy and bond formation releases energy.
d. Bond breaking and bond formation both releases energy.
10.
Hess’s Law makes it possible to
a. balance equations.
b. predict the products in a reaction.
c. determine the specific heat of a substance.
d. determine the enthalpy change of a reaction.
11. The quantity H is equal to
a. Hproduct./.Hreactant.
c. Hreactant – Hproduct.
12.
13.
b. Hproduct + Hreactant .
d. Hproduct - Hreactant .
Which serves as a unit of heat?
a. degree Celcius
b. degree Fahrenheit
c. Kelvin
d. joule
(1) AB + 50KJ ----- C + D
(2) A + B ------ CD + 75KJ
(3) AB ------- C + D H=90KJ
(4) A + B ------ CD H= -45 KJ
Which reactions are exothermic?
a. (1) & (2)
b. (2) + (4)
c. (2) & (4)
d. (1) & (3)
Use the following graph to answer #14 -#16:
14. The enthalpy change ( H) for the above reaction is _____ KJ.
a. 2
b. –2
c. 4
d.-4
15. This is a (an)____________ reaction.
a. physical
b. exothermic
c. endothermic
16. What is the enthalpy change if 3 moles of A is used in the reaction?
a. 8 KJ
b. –8 KJ
c. 16KJ
d. -16KJ
Short Answers: Show all work (20 points each)
17. .52 g of paraffin is burnt to heat 100g of water. The original temperature is 20 oC. The final
temperature is 72.2oC.
a. Calculate the amount of energy absorbed by water.
b. How much heat is released by paraffin?
c. Calculate the heat of combustion of paraffin (in J/g).
d. Change J/g to KJ/g.
e. The standard heat of combustion of paraffin is 42.0KJ/g. What is the % error of the
result?
18. Calculate the following amount of energy involved in heating 150 g of ice starting –76oC to
steam at 130oC using the following data for water: Hfus = 336J/g , Hvap = 2260J/g ,
C(ice) = 2.06J/g , C (steam) = 2.02J/g , C (water) = 4.18 J/g oC
a. energy to heat the ice to 0oC?
b. energy to melt the ice?
c. energy to heat liquid water from 0oC to 100oC?
d. energy to boil water?
e. energy to heat the steam from 100oC to 114oC?
f. the total energy to cool 150 g steam at 130 oC to –76oC?