# 4 Problems on Energy

5 Problems on Energy From Test Fall 2001 The internal energy of a system is always increased by a. adding heat to the system and having the surroundings do work on the system. b. adding heat to the system and having the system do work on the surroundings. c. withdrawing heat from the system and having the surroundings do work on the system. d. withdrawing heat from the system and having the system do work on the surroundings

The internal energy of a system is always increased by To increase E, we need to make it more positive. E= q+w We need to add heat to the system (q positive) and do work on the system (w positive). The internal energy of a system is always increased by a. adding heat to the system and having the

surroundings do work on the system. b. adding heat to the system and having the system do work on the surroundings. c. withdrawing heat from the system and having the surroundings do work on the system. d. withdrawing heat from the system and having the system do work on the surroundings The internal energy of a system is always increased by a. adding heat to the system and having the surroundings do work on the system. b. adding heat to the system and having the

system do work on the surroundings. c. withdrawing heat from the system and having the surroundings do work on the system. d. withdrawing heat from the system and having the system do work on the surroundings E>0 for a If E = 292 kJ for a system that performs 213 kJ of work on its surroundings, which of the following statements is correct? a. The system loses 79 kJ of heat. b. The system gains 79 kJ of heat.

c. The system loses 505 kJ of heat. d. The system gains 505 kJ of heat. If E = 292 kJ for a system that performs 213 kJ of work on its surroundings, which of the following statements is correct? a. The system loses 79 kJ of heat. b. The system gains 79 kJ of heat. c. The system loses 505 kJ of heat.

d. The system gains 505 kJ of heat. E q w 292 kJ q 213 kJ q - 292 213 kJ 79 kJ Which one of the following is a correct statement for the combustion of methane? CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) a. The reaction is exothermic and H is positive.

b. The reaction is endothermic and H is negative. c. The reaction is endothermic and H is positive. d. The reaction is exothermic and H is negative. Which one of the following is a correct statement for the combustion of methane? CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)

a. The reaction is exothermic and H is positive. b. The reaction is endothermic and H is negative. c. The reaction is endothermic and H is positive. d. The reaction is exothermic and H is negative. The combustion reaction above is exothermic, which means that H is negative What is the value of H when 5.75 g of CO(g) reacts completely with hydrogen to form CH3OH(l)?

CO(g) + 2 H2(g) CH3OH(l) H = -128.1 kJ a. 26.3 kJ c. 26.3 kJ b. 128.1 kJ d. 128.1 kJ What is the value of H when 5.75 g of CO(g) reacts completely with hydrogen to form CH3OH(l)? CO(g) + 2 H2(g) CH3OH(l) H = -128.1 kJ a. 26.3 kJ c. 26.3 kJ

b. 128.1 kJ d. 128.1 kJ 128.1 kJ 1 mol CO H 5.75 g CO 1 mol CO 28.01 g CO 26.3 kJ Consider the hypothetical chemical reaction shown below: 3 X2(g) 2 X3(g)

H = -333 kJ If the atomic weight of X is 66.6 g/mol, what is H for conversion of 11.1 g of X2(g) to X3(g)? a. 2.00 kJ c. +9.25 kJ b. +2.00 kJ d. 9.25 kJ Consider the hypothetical chemical reaction shown below: 3 X2(g) 2 X3(g) H = -333 kJ

If the atomic weight of X is 66.6 g/mol, what is H for conversion of 11.1 g of X2(g) to X3(g)? a. 2.00 kJ b. +2.00 kJ c. +9.25 kJ d. 9.25 kJ 1 mol X 2 333 kJ H 11.1 g X 2 3 mol X 2 66.6 2 g X 2

9.25 kJ

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