Lab: Enthalpy Answers

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Answers:
Selection 1:negative
.:gives off heat
3

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Answers:
Selection 1:positive
.:absorbs heat
4

The enthalpy of an icepack is because the reaction .

A
absorbs heat
B
gives off heat
C
does not change temperature
6

If you reverse Reaction 2 and combine the reactions, which substances do not cancel? Check all that apply. 2

A
Option
B
Option
C
Option
D
Option
E
Option
F
2
G
Option
8

Suppose that during the experiment, a student forgot to put the lid on the calorimeter. What is the most likely error and reason?Temperature readings will be too high because heat will be absorbed by the air.Temperature readings will be too high because the lidless coffee cups will give off heat.Temperature readings will be too low because heat will be absorbed by the air.The temperature readings will be too low because the lidless coffee cup will absorb more heat.

A
Temperature readings will be too high because heat will be absorbed by the air.
B
Temperature readings will be too high because the lidless coffee cups will give off heat.
C
Temperature readings will be too low because heat will be absorbed by the air.
D
The temperature readings will be too low because the lidless coffee cup will absorb more heat.
9

The actual enthalpy of the magnesium flare reaction is –603 kJ/mol. Your experimental value was likely different. Check all that apply.The coffee cup calorimeter may have absorbed some heat.The plastic coffee cup lid may have allowed some heat to escape.The thermometer did not measure the temperature of the solution properly.Reading the maximum temperature values from the thermometer could be challenging.

A
The coffee cup calorimeter may have absorbed some heat.
B
The plastic coffee cup lid may have allowed some heat to escape.
C
The thermometer did not measure the temperature of the solution properly.
D
Reading the maximum temperature values from the thermometer could be challenging.
11

Many fuels, such as gasoline and diesel fuel, are hydrocarbons. Hydrocarbons are molecules that contain only hydrogen and carbon. Choose all of the criteria below that would make a hydrocarbon a good fuel in terms of enthalpy. Hydrocarbons burn to absorb a large amount of energy.Burning hydrocarbons produces a lot of energy.Breaking carbon-hydrogen and carbon-carbon bonds gives off energy.The enthalpy of combustion is a large negative value.

A
Hydrocarbons burn to absorb a large amount of energy.
B
Burning hydrocarbons produces a lot of energy.
C
Breaking carbon-hydrogen and carbon-carbon bonds gives off energy.
D
The enthalpy of combustion is a large negative value.
12

Magnesium combustion heat.

A
gives off a little
B
gives off a lot of
C
absorbs a little
D
absorbs a lot of

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