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

Study Guide - Practice Questions

Study Guide - Flashcards