AnswersChemistry A.1 - F26 - Jacob MetskerLab: Calorimetry and Specific Heat

Lab: Calorimetry and Specific Heat — Unit test Answers

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1
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Two metal blocks that have slightly different temperatures are placed next to one another. After five minutes, they both have lower but equal temperatures. According to the law of conservation of energy, what most likely happened?

A
Energy was created inside the blocks.
B
Energy was destroyed inside the blocks.
C
Energy was absorbed into the blocks from outside the system.
D
Energy was transferred from the warmer block to the cooler block.
2
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Which describes the enthalpy change associated with an endothermic reaction?

A
It is negative because the enthalpy of the products is greater than the enthalpy of the reactants.
B
It is positive because the enthalpy of the products is greater than the enthalpy of the reactants.
C
It is negative because the enthalpy of the reactants is greater than the enthalpy of the products.
D
It is positive because the enthalpy of the reactants is greater than the enthalpy of the products.
3

Which statement about enthalpy is true?

A
The enthalpy of formation for a pure element in its standard state is always positive.
B
The enthalpy of formation for a pure element in its standard state is always negative.
C
Enthalpy is a state function because its change depends only on initial and final conditions.
D
Enthalpy is not a state function because its change depends on the identities of the reactants and products.
4

Which statement best describes the direction of heat flow by conduction between two samples of the same material?

A
Heat flows from faster molecules to slower molecules when they are near.
B
Heat flows from faster molecules to slower molecules when they collide.
C
Heat flows from slower molecules to faster molecules when they are near.
D
Heat flows from slower molecules to faster molecules when they collide.
5

Which reaction is endothermic?

A
HCl + NaOH NaCl + H2O + 58 kJ
Option A
B
6CO2 + 12H2O + energy C6H12O6 + 6O2 + 6H2O
Option B
C
2Na + Cl2 2NaCl + energy
Option C
D
2C2H6 + 7O2 4CO2 + 6H2O + 2,502 kJ
Option D
6

Which is the best example of how electromagnetic energy is used?

A
a pot of boiling water on a gas stove
B
a patient receiving an X-ray in a hospital
C
a car burning gasoline to power the engine
D
a car of a roller coaster moving quickly down a slope
7

A metal sample is heated and placed into the water in a calorimeter at room temperature. Which statement best describes how the calorimeter can be used to determine the specific heat capacity of the metal sample?

A
Energy transfers to the metal from the water and calorimeter until they are all at room temperature.
B
Energy transfers from the metal to the water and calorimeter until they are all at room temperature.
C
Energy transfers to the metal from the water and calorimeter until they all reach a single temperature.
D
Energy transfers from the metal to the water and calorimeter until they all reach a single temperature.
8

What explains the key difference between a bomb calorimeter and a coffee cup calorimeter?

A
A bomb calorimeter is 10 times larger but works the same way.
B
A bomb calorimeter measures heat for liquid products only.
C
A bomb calorimeter has a separate chamber to hold substances and can even measure heat gain or loss for reactions that do not occur in water.
D
A bomb calorimeter can measure heat gain or loss in gaseous reactions but is not useful for reactions that occur at high pressures and temperatures.
9

Complete combustion of a 0.350 g sample of a compound in a bomb calorimeter releases 14.0 kJ of heat. The bomb calorimeter has a mass of 1.20 kg and a specific heat of 3.55 J/(gi°C). If the initial temperature of the calorimeter is 22.5°C, what is its final temperature?Use .

Question illustration
A
19.2°C
B
25.8°C
C
34.2°C
D
72.3°C
10

Which statement defines calorimetry?

A
the conservation of energy
B
a unit of energy that is used when calculating energy exchange
C
a device that is used to measure the heat that is gained or lost during a chemical change
D
the measurement of energy that is given off or absorbed in a physical or chemical process
11

Ammonia, NH3 (Hf = –45.9 kJ), reacts with oxygen to produce water (Hf = –241.8 kJ) and nitric oxide, NO (Hf = 91.3 kJ), in the following reaction:What is the enthalpy change for this reaction? Use .

Question illustration
A
–902 kJ
B
–104.6 kJ
C
104.6 kJ
D
900.8 kJ
12

Nitrogen dioxide, NO2(g) (Hf = 33.84 kJ/mol), is decomposed according to the following reaction:What is the enthalpy change when 2.50 mol of nitrogen dioxide decomposes? Use .

Question illustration
A
13.5 kJ of energy released
B
13.5 kJ of energy absorbed
C
84.6 kJ of energy released
D
84.6 kJ of energy absorbed
13

A welding torch produces a flame by burning acetylene fuel in the presence of oxygen. This flame is used to melt a metal. Which energy transformation represents this process?

A
chemical energy into thermal energy
B
kinetic energy into potential energy
C
kinetic energy into electromagnetic energy
D
potential energy into chemical energy
14

Which best describes heat?

A
energy that is carried by electric and magnetic fields
B
energy that decreases as a car slows to a stop
C
energy that increases as a book is lifted to a higher shelf
D
energy that flows from a hot mug of tea to a cold hand
15

Which direction does thermal energy flow in the following diagram?

Question illustration
A
Heat flows from the ice cream to the hand.
B
Heat flows from the hand to the ice cream.
C
The system is in a state of equilibrium.
D
The system is too cold for heat to move.
16

How should the baking of a pizza be categorized?

A
as an exothermic process because the dough releases heat
B
as an endothermic process because the dough releases heat
C
as an exothermic process because the dough absorbs heat
D
as an endothermic process because the dough absorbs heat
17

Nitrogen reacts with hydrogen to form ammonia according to the equation below.Standard Enthalpies of FormationSubstanceDHf (kJ/mol)C2 H2 (g)–26.7NH3 (g)–46.19HBr (g)236.23HCl (g)–92.30HF (g)–268.6HI (g)25.9NaCl (s)–411.0Based on the equation and the information in the table, what is the enthalpy of the reaction?

Question illustration
A
Hrxn = 46.19 kJ
Option A
B
Hrxn = –46.19 kJ
Option B
C
Hrxn = 92.38 kJ
Option C
D
Hrxn = –92.38 kJ
Option D
18

A sample of an unknown substance has a mass of 0.465 kg. If 3,000.0 J of heat is required to heat the substance from 50.0°C to 100.0°C, what is the specific heat of the substance?Use .

Question illustration
A
0.00775 J/(gi°C)
B
0.0600 J/(gi°C)
C
0.129 J/(gi°C)
D
0.155 J/(gi°C)
19

The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must happen at the molecular level?

A
The molecules move more quickly and their average kinetic energy increases.
B
The molecules move more slowly and their average kinetic energy decreases.
C
The molecules move more quickly and their average kinetic energy decreases.
D
The molecules move more slowly and their average kinetic energy increases.
20

Which units express heat capacity?

A
J/°C, J/K, cal/°C, cal/K
B
J/(gi°C), J/(giK), cal/(gi°C), cal/(giK)
C
J, cal
D
°C, K

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