Question 1

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

Energy can be converted from one form to another, but it is neither created nor destroyed.

Question 2

A system absorbs 200 J of heat from the surroundings and does 50 J of work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 150\ \mathrm{J}$$

Question 3

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 4

What is the correct relationship for enthalpy ($$H) in $$terms of internal energy ($$E$$), pressure ($$P$$), and volume ($$V$$)?

Accepted Answer

$$H = E + PV$$

Question 5

A chemical reaction occurs at constant pressure and releases 300 kJ of heat. What is the sign and value of $$\Delta H$$ for this reaction?

Accepted Answer

$$\Delta H = -300\ \mathrm{kJ}$$

Question 6

Which of the following statements about exothermic and endothermic processes is correct?

Accepted Answer

An exothermic process releases heat to the surroundings.

Question 7

Calculate the quantity of heat ($$q) $$absorbed by 100.0 g of water ($$c = 4.18\ \mathrm{J/g\cdot K}) if $$its temperature increases from 25.0°C to 75.0°C.

Accepted Answer

$$q = 20,900\ \mathrm{J}$$

Question 8

Which type of system allows both mass and energy to be exchanged with the surroundings?

Accepted Answer

Open system

Question 9

In a bomb calorimeter, which of the following is measured directly?

Accepted Answer

Change in internal energy ($$\Delta E)$$

Question 10

Which of the following best explains why bond enthalpy is always a positive value?

Accepted Answer

Energy is required to break chemical bonds.

Question 11

A reaction has $$\Delta H = -500\ \mathrm{kJ}. $$What can you conclude about this reaction?

Accepted Answer

It is exothermic and releases 500 kJ of heat.

Question 12

Which of the following is NOT a guideline for writing thermochemical equations?

Accepted Answer

The enthalpy change for a reaction is equal in magnitude and sign to the reverse reaction.

Question 13

Which equation correctly relates the change in enthalpy ($$\Delta H) to $$the change in internal energy ($$\Delta E) at $$constant pressure?

Accepted Answer

$$\Delta H = \Delta E + P\Delta V$$

Question 14

A 0.500 g sample of a substance is burned in a bomb calorimeter, causing the temperature of the calorimeter to increase by 2.00°C. If the heat capacity of the calorimeter is 10.0 kJ/°C, what is the heat released per gram of the substance?

Accepted Answer

$$20.0\ \mathrm{kJ/g}$$

Question 15

Which of the following statements about standard enthalpy of formation ($$\Delta H_f^\circ) is $$correct?

Accepted Answer

It is the enthalpy change for forming one mole of a compound from its elements in their standard states.

Question 16

Using Hess's Law, which of the following is true?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for each step in a series of reactions.

Question 17

Which of the following best describes an isolated system?

Accepted Answer

It cannot exchange heat or mass with its surroundings.

Question 18

A solar-heated home uses rocks to store heat. If 100.0 kg of rocks (specific heat = $$0.82\ \mathrm{J/g\cdot K}) $$cool from 50.0°C to 20.0°C overnight, how much heat is released?

Accepted Answer

$$2.46 	imes 10^6$\ \mathrm{J}$$

Question 19

Which of the following is true about the sign conventions for $$q$$, $$w$$, and $$\Delta E$$?

Accepted Answer

A negative $$w$$ means work is done by the system.

Chapter 5: Thermochemistry – Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드