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Coppin State College Department of Natural Sciences Chemistry 101 Examination #6 Chapter 6 (Dr. Amah)
Name ______Last First This examination contains thirty (20) multiple choice questions with five (5) responses. There is only one correct response for each question. Time: 120 minutes.
1. How many calories are equivalent to 158 joules?
a. 0.0265 cal b. 8.31 cal c. 22.1 cal d. 37.8 cal e. 661 cal.
2. Heat capacity is defined as
a. the amount of heat required to raise the temperature of a substance by 1 K b. the amount of heat required to raise the temperature of 1 grams of substance by 1K c. 4.18 J/g.K d. 4.18J/K e. 4.18 cal/g.K
3. How many joules are equivalent to 364 calories ?
a. 1.33 J b. 1523 J c. 87.0 J d. 24.0 J e. 0.364 J
4. When two solutions are mixed, the container ‘feels cold.” Thus, a. the reaction is endothermic. b. the reaction is exothermic. c. the energy of the universe is increased. d. the energy of both the system and surrounding is decreased. e. The energy of the system is increased. 2
5. Which response lists the processes that are endothermic and none that are exothermic?
1. Evaporation of water 2. Sublimation of ice 3. Condensation of steam 4. Freezing of water
a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 3 and 4 only e. 2,3, and 4 only.
6. Which process involves the largest energy change for one mole of 1,4- dichlorobenzene, moth balls, when it changes from solid to gas?
a. ▲ H vaporization b. ▲ H sublimation c. ▲ H boiling d. ▲ H fusion e. ▲ H condensation
7. Consider the thermal energy transfer process during a chemical process. When heat is absorbed by the system, the process is said to be ______and the sign of H is ______
a. exothermic, positive b. exothermic, negative c. endothermic, positive d. endothermic, negative e. enthalpic, negative.
8. For the general reaction 2A + B2 2AB, H is - 50.0 KJ. We can conclude that
a. the reaction is exothermic b. the surrounding absorb energy c. the reaction is endothermic d. the bond energy of each A-B bond is 50.0 KJ e. the molecule AB contains less energy than A or B2 3
9. Calculate the standard enthalpy change for the reaction:
C2H2(g) + H2(g) C2H4(g)
based on the following standard enthalpies of formation:
0 H [ C2H2(g)] = +226.7 KJ/mol 0 H [ C2H4(g)] = +52.3 KJ/mol 0 H [H2(g)] = 0.0 KJ/mol
a. 174.4 KJ b. –56.4 KJ c. –174.4 KJ d. –279.0 KJ e. –321.1 KJ
10. Calculate the standard enthalpy of formation of carbon monoxide,
C(s) + ½ O2(g) CO(g) given the enthalpies of the reactions given below.
0 C(s) + O2(g) CO2(g) H = -393.5 KJ
0 2CO(g) + O2(g) 2CO2(g) H = -566.0 KJ
a. –959.6 KJ b. –421.6 KJ c. –172.5 KJ d. –110.5 KJ e. 172.5 KJ
11. All of the following statements are true EXCEPT
a. energy is neither created nor destroyed in chemical reactions b. spontaneous reactions are always exothermic c. kinetic energy is the energy associated with motion d. energy is the capacity to do work e. increasing the thermal energy of a gas increases the motion of its atoms. 4
12. If 34.8 J is required to change the temperature of 10.0g of mercury by 25 K, what is the specific heat of mercury?
a. 0.139 J/g.K b. 0.338 J/g.KJ c. 0.718 J/g.K d. 0.870 J/g.K e. 1.93 J/g.K
0 13. If 1.00 mol of H2O at 25 C absorbs 1.00 KJ of heat, what is the final temperature of the water? The specific heat of water is 4.184 J/g.K.
a. 11.7 0C b. 32.9 0C c. 38.3 0C d. 52.1 0C e. 70.9 0C
14. Ethylene glycol has a specific heat of 0.578 cal/(g.0C). If 23.2 g of ethylene glycol absorbs 75.6 cal of heat energy, what will the final temperature increase be?
a. 0.770C b. 1.880C c. 5.640C d. 1.01 x 103 0C e. 3.03 x 103 0C
15. When a sample of aqueous hydrochloric acid was neutralized with aqueous sodium hydroxide in a calorimeter, the temperature of 100.0 g of water surrounding the reaction increased from 25.0 0C to 31.5 0C. If the specific heat of water is 1.00 cal/(g.0C), calculate the quantity of energy in calories involved in this neutralization reaction.
a. 1250 cal b. 650 cal c. 1000 cal d. 100.0 cal e. 6.50 cal
16. When the cold-pack is activated, a chemical reaction occurs and the temperature of the pack contents drops sharply. Which of the following is a correct description of the reaction occurring in the pack? a. the reaction is exothermic; ▲ H0 > 0 b. the reaction is exothermic; ▲ H0 < 0 c. the reaction is endothermic;▲ H0 > 0 d. the reaction is endothermic; ▲ H0 < 0 e. None of the above statements is correct. 5
17. All of the following statements are true EXCEPT
a. Energy is neither created nor destroyed in chemical reactions. b. Kinetic energy is the energy associated with motion. c. Energy is the capacity to do work. d. Increasing the thermal energy of a gas increases the motions of its atoms e. Spontaneous reactions are always exothermic
18. All of the following statements are true EXCEPT
a. In an endothermic process heat is transferred from the surrounding to the system. b. The greater the specific heat of an object, the more thermal energy it can store c. The SI unit of specific heat capacity is joules per gram per Kelvin d. Heat is transferred from the system to the surrounding in an exothermic process. e. The temperature of a system is a state function
19. Commercial cold packs consist of solid ammonium nitrate and water. NH4NO3 absorbs 330 J of heat per gram dissolved in water. In a coffee-cup calorimeter, 3.00g. NH4NO3 is dissolved in 100.00 g of water at 24.0 0C. What is the final temperature of the solution? Assume that the total mass of the solution is 103.00 g and has a specific heat of 4.184 J/g.K.
a. 11.0 0C b. 15.9 0C c. 19.1 0C d. 21.7 0C e. 35.9 0C
20. A chemical reaction in a bomb calorimeter evolves 4.12 kJ of heat. If the temperature of the calorimeter increases from 18.20 0C to 22.79 0C, what is the heat capacity of the calorimeter
a. 1.11 kJ/0C b. 4.12 kJ/0C c. 4.59 kJ/0C d. 189 kJ/0C e. 898 kJ/0C
21. How much energy is required to change the temperature of 15.0 g of Fe from 18.5 oC to 56.8 oC? The Specific heat of iron is 0.451 J/g.K.
a. 57.5 J b. 127 J c. 259 J d. 385 J e. 452 J 6
Q = Ms x ▲ Ts x SHs
▲H = HP - HR 2 K.E. = ½ M.V