AnswersSY2026-27 - 2003340 Chemistry 1 Sem 2 CRLab: Enthalpy

Lab: Enthalpy — Unit test Answers

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1
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The overall change in enthalpy of a reaction depends only on

A
the reactants and the products.
B
the path that is taken from the reactants to the products.
C
the reactants and the catalysts only.
D
the reactants, the products, and the catalysts.
2
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According to Hess’s law, if a series of intermediate reactions are combined, the enthalpy change of the overall reaction is

A
the difference between the enthalpies of the intermediate reactions.
B
the sum of the enthalpy changes of the intermediate reactions.
C
the product of the enthalpy changes of the intermediate reactions.
D
the fraction of the individual enthalpies of the intermediate reactions.
3

Consider the following intermediate chemical equations.What is the enthalpy of the overall chemical reaction ?

Question illustration
A
-4,580 kJ
B
-1,300 kJ
C
1,300 kJ
D
4,580 kJ
4

Which energy changes are associated with a liquid freezing?

A
Energy is released as potential energy increases.
B
Energy is absorbed as potential energy increases.
C
Energy is released as potential energy decreases.
D
Energy is absorbed as potential energy decreases.
5

Which statement describes mechanical energy?

A
the energy that is stored in chemical bonds
B
the energy that is associated with temperature
C
the sum of the kinetic energy and the potential energy of an object
D
the type of energy that is associated with electromagnetic radiation
6

Which statement describes the law of conservation of energy?

A
All systems will exchange matter and energy with their surroundings.
B
All systems can exchange energy, but not matter, with their surroundings.
C
Energy cannot be created nor destroyed, but it changes from one form to another.
D
Energy is destroyed in most chemical reactions when new products are formed.
7

A sample of octane (C8H18) that has a mass of 0.750 g is burned in a bomb calorimeter. As a result, the temperature of the calorimeter increases from 21.0°C to 41.0°C. The specific heat of the calorimeter is 1.50 J/(g • °C), and its mass is 1.00 kg. How much heat is released during the combustion of this sample?Use .

Question illustration
A
22.5 kJ
B
30.0 kJ
C
31.5 kJ
D
61.5 kJ
8

Carbon reacts with oxygen to produce carbon dioxide (CO2 (g), Hf = –393.5 kJ/mol) according to the equation below.What is the enthalpy change of the reaction? Use .

Question illustration
A
–393.5 kJ
B
–196.8 kJ
C
196.8 kJ
D
393.5 kJ
9

A book is falling from the top shelf of a bookcase. Which statement correctly describes the change in the energy of the book?

A
The potential energy and kinetic energy remain the same.
B
The potential energy decreases as kinetic energy increases.
C
The kinetic energy decreases as potential energy increases.
D
The kinetic energy remains at zero, but potential energy increases.
10

Which substance has Hf defined as 0 kJ/mol?

Question illustration
A
H2O (s)
B
Ne (l)
C
F2 (g)
D
CO2 (g)
11

Propane (C3 H8 (g), Hf = –103.8 kJ/mol) reacts with oxygen to produce carbon dioxide (CO2 , Hf = –393.5 kJ/mol ) and water (H2 O, Hf = –241.82 kJ/mol) according to the equation below.What is the enthalpy of combustion (per mole) of C3 H8 (g)? Use .

Question illustration
A
–2,044.0 kJ/mol
B
–531.5 kJ/mol
C
531.5 kJ/mol
D
2,044.0 kJ/mol
12

An ice cube is dropped into a glass of milk at 20°C. Which statement explains the transfer of kinetic energy (KE)?

A
Because milk has higher KE than ice, KE is transferred from the milk to the molecules of ice.
B
Because milk has higher KE than ice, KE is transferred from the molecules of ice to the milk.
C
Because ice has higher KE than milk, KE is transferred from the milk to the molecules of ice.
D
Because ice has higher KE than milk, KE is transferred from the molecules of ice to the milk.
13

The molar heat of fusion of gold is 12.550 kJ mol–1. At its melting point, how much mass of melted gold must solidify to release 235.0 kJ of energy?Use .

Question illustration
A
18.73 g
B
222.5 g
C
2,949.3 g
D
3,688.3 g
14

Digby wants to determine how many calories are in his bag of chips. Which calorimeter should he use?

A
coffee cup calorimeter
B
bomb calorimeter
C
He could use both types of calorimeters.
D
He cannot use either.
15

According to the enthalpy diagram below, which of the following statements is true?

Question illustration
A
Arrows A and D represent the enthalpy of the intermediate chemical reactions.
B
Arrow C represents the enthalpy of the overall chemical reaction.
C
Arrow C indicates that the third intermediate reaction is exothermic.
D
Arrow B indicates that the second intermediate reaction is exothermic.

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