Answers25-26 KCS18 Chemistry ICHeat

Heat — Test Answers

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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
2
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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
3

Reactant P contains 50 J of energy, and reactant Q contains 35.3 J of energy. The reactants combine to form product PQ, which contains 104 J of energy. What is the energy transformation?

A
Energy is absorbed because the product has more energy than the reactants have.
B
Energy is absorbed because the product has less energy than the reactants have.
C
Energy is lost because the product has more energy than the reactants have.
D
Energy is lost because the product has less energy than the reactants have.
4

When ammonium chloride is dissolved in water, the beaker gets cold. Which type of reaction does this describe?

A
exothermic
B
endothermic
C
both exothermic and endothermic
D
neither exothermic nor endothermic
5

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.
6

Which statement defines specific heat capacity for a given sample?

A
the temperature of a given sample
B
the temperature that a given sample can withstand
C
the quantity of heat that is required to raise the sample’s temperature by 1°C (Kelvin)
D
the quantity of heat that is required to raise 1 g of the sample by 1°C (Kelvin) at a constant pressure
7

Which energy change takes place when gasoline evaporates from a fuel gas can?

A
Energy is released.
B
Energy is absorbed.
C
Energy remains stationary.
D
Energy becomes transformed.
8

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.
9

Which defines the average kinetic energy of a system’s particles?

A
density
B
pressure
C
temperature
D
volume
10

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
11

The combustion of glucose, C6 H12 O6 (s), produces carbon dioxide, CO2 (g), and water, H2 O(g), according to the equation below.The enthalpy of the reaction is –2,840 kJ. What is the heat of combustion, per mole, of glucose?

Question illustration
A
–2,840 kJ/mol
B
–473.3 kJ/mol
C
473.3 kJ/mol
D
2,840 kJ/mol
12

The molar heat of fusion for water is 6.01 kJ/mol. How much energy is released when 36.8 g of water freezes at its freezing point?Use .

Question illustration
A
6.12 kJ
B
12.3 kJ
C
108 kJ
D
221 kJ
13

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.
14

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
15

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.

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