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Thermochemical Equations — Unit test Answers

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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
2
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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
3

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
4

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.
5

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.
6

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
7

Which statement best explains the change that occurs when gas particles move more slowly?

A
The temperature increases because the average kinetic energy decreases.
B
The temperature increases because the average kinetic energy increases.
C
The temperature decreases because the average kinetic energy decreases.
D
The temperature decreases because the average kinetic energy increases.
8

Which substance has Hf defined as 0 kJ/mol?

Question illustration
A
H2O (s)
B
Ne (l)
C
F2 (g)
D
CO2 (g)
9

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
10

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.
11

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

A
density
B
pressure
C
temperature
D
volume
12

A copper rod that has a mass of 200.0 g has an initial temperature of 20.0°C and is heated to 40.0°C. If 1,540 J of heat are needed to heat the rod, what is the specific heat of copper?Use .

Question illustration
A
0.0130 J/(gi°C)
B
0.0649 J/(gi°C)
C
0.193 J/(gi°C)
D
0.385 J/(gi°C)
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

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

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

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