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WorksheetsEnergy 2: Energy Profile & Calorimetry
Total questions: 24
Worksheet time: 2hrs 56mins
Name
Class
Date
1.
Which of the following correctly states the energy changes occurring when chemical bonds are formed and broken?
a)
Energy is released when bonds are formed and when they are broken.
b)
Energy is absorbed when bonds are formed and when they are broken.
c)
Energy is absorbed when bonds are formed and released when they are broken.
d)
Energy is released when bonds are formed and absorbed when they are broken.
2.
The following is a thermochemical equation for the complete combustion of ethane:
2C2H6(g)+7O2(g)→4CO2(g)+6H2O(g); ΔH=-3114 kJ/mol
If the activation energy of the reaction is 275 kJ per mol of ethane, the energy released, in kJ, during bond formation for the reaction as written above will be
2C2H6(g)+7O2(g)→4CO2(g)+6H2O(g); ΔH=-3114 kJ/mol
If the activation energy of the reaction is 275 kJ per mol of ethane, the energy released, in kJ, during bond formation for the reaction as written above will be
a)
2564
b)
2839
c)
3389
d)
3664
3.
Nitrogen reacts with hydrogen to produce ammonia according to the following equation:
N2(g)+3H2(g)→2NH3(g); ΔH=-92 kJ mol-1
The energy change for this reaction is best described as
N2(g)+3H2(g)→2NH3(g); ΔH=-92 kJ mol-1
The energy change for this reaction is best described as
a)
exothermic, because the net strength of the bonds in the products is greater than the net strength of the bonds in the reactants
b)
endothermic, because the net strength of the bonds in the products is greater than the net strength of the bonds in the reactants
c)
exothermic, because the net strength of the bonds in the products is less than the net strength of the bonds in the reactants
d)
endothermic, because the net strength of the bonds in the products is less than the net strength of the bonds in the reactants
4.
The following reaction can occur to completion in aqueous solution:
CH3Cl(aq)+OH-(aq)→CH3OH(aq)+Cl-(aq)
The energy change during this process is illustrated by the energy profile shown.
A reaction can occur between a CH3Cl molecule and a hydroxide ion
CH3Cl(aq)+OH-(aq)→CH3OH(aq)+Cl-(aq)
The energy change during this process is illustrated by the energy profile shown.
A reaction can occur between a CH3Cl molecule and a hydroxide ion
a)
every time they collide
b)
only when they collide with exactly the energy X
c)
only when they collide with an energy equal to Y-Z
d)
only when they collide with energy greater than or equal to energy X
5.
The following energy profile relates to the two reactions:
2Cu(s)+O2→2CuO(s); ΔH=-312 kJ mol-1
2Cu(s)+0.5O2→Cu2O(s); ΔH=-170 kJ mol-1
The value of ΔH, in kJ mol-1, for the reaction
4CuO(s)→2Cu2O(s)+O2(g)
is
2Cu(s)+O2→2CuO(s); ΔH=-312 kJ mol-1
2Cu(s)+0.5O2→Cu2O(s); ΔH=-170 kJ mol-1
The value of ΔH, in kJ mol-1, for the reaction
4CuO(s)→2Cu2O(s)+O2(g)
is
a)
+284
b)
+142
c)
-142
d)
-284
6.
The change in energy during a reaction is represented in the energy profile diagram shown.
The change in energy labelled ΔE above is
The change in energy labelled ΔE above is
a)
the energy absorbed when bonds in the reactants break
b)
the activation energy of the forward reaction
c)
the activation energy for the reverse reaction
d)
the heat of reaction
7.
Consider the following energy profile diagram for a reaction represented by the equation X+Y→Z
Which one of the following provides the correct values of the activation energy (in kJ mol-1) and the ΔH (in kJ mol-1) for the reaction
Which one of the following provides the correct values of the activation energy (in kJ mol-1) and the ΔH (in kJ mol-1) for the reaction
a)
Activation Energy = +75; ΔH = +100
b)
Activation Energy = +100; ΔH = +175
c)
Activation Energy = +175; ΔH = +100
d)
Activation Energy = +200; ΔH = -125
8.
Shown is the energy profile for combustion of methane according to the equation:
CH4(g)+2O2(g)→CO2(g)+2H2O(g)
According to the information provided on this profile, the activation energy for the reaction:
0.5CO2(g)+H2O(g)→0.5CH4(g)+O2(g)
would be
CH4(g)+2O2(g)→CO2(g)+2H2O(g)
According to the information provided on this profile, the activation energy for the reaction:
0.5CO2(g)+H2O(g)→0.5CH4(g)+O2(g)
would be
a)
1635 kJ
b)
2135 kJ
c)
2490 kJ
d)
4270 kJ
9.
An energy profile for a reversible chemical reaction is shown. According to this profile, the activation energy of the reverse reaction is equal to
a)
D
b)
C - B
c)
A - B
d)
C- D
10.
Shown is the energy profile for the reaction described by the equation:
2H2(g)+O2(g)→2H2O(g)
According to the information in this profile, the energy, in kJ, released during the formation of the O-H bonds in one mole of water vapour is
2H2(g)+O2(g)→2H2O(g)
According to the information in this profile, the energy, in kJ, released during the formation of the O-H bonds in one mole of water vapour is
a)
286 kJ
b)
572 kJ
c)
971 kJ
d)
1942 kJ
11.
Consider the energy profile for a particular reaction.
Which of the following is an INCORRECT conclusion from the data presented?
Which of the following is an INCORRECT conclusion from the data presented?
a)
It takes more energy to break the bonds in the reactants than the energy released when the products form
b)
The activation energy of the reverse reaction is x+y
c)
The magnitude of the heat of reaction is equal to z-x
d)
When the products form, after bonds in the reactants are broken, energy equivalent to x+y-z is released.
12.
The energy profiles of two reactions are shown.
The reaction with the lowest activation energy is
The reaction with the lowest activation energy is
a)
A+B → C+D
b)
X→ Y+Z
c)
C+D → A+B
d)
Z+Y →X
13.
A calorimeter is calibrated chemically by measuring the temperature change caused by the combustion of precisely 1.131 g of benzoic acid. The enthalpy of combustion of benzoic acid is given by the thermochemical equation below:
2C6H5COOH(s)+15O2(g)→14CO2(g)+6H2O(l); ΔH=-6454 kJ/mol
If the temperature increases by 30.94°C, the calibration factor of the calorimeter (in J/°C) is
2C6H5COOH(s)+15O2(g)→14CO2(g)+6H2O(l); ΔH=-6454 kJ/mol
If the temperature increases by 30.94°C, the calibration factor of the calorimeter (in J/°C) is
a)
208.5
b)
966.9
c)
1934
d)
3868
14.
A solution calorimeter was inadvertently calibrated with 105 mL of water instead of 100 mL. The calorimeter was emptied and dried and then used to determine the heat of reaction of powdered zinc in 100 mL of HCl (aq). It can be deduced from this information that the correct calibration factor should be
a)
Lower and the heat of reaction should be lower.
b)
Higher and the heat of reaction should be higher.
c)
Lower and the heat of reaction should be higher.
d)
Higher and the heat of reaction should be lower.
15.
0.60 g of ethanol is burnt in a bomb calorimeter. The temperature of the calorimeter contents rises from 12.8°C to 24.5°C. ∆H for the reaction is -1364 kJ/mol. The calibration factor of the calorimeter is, in J/°C,
a)
550
b)
760
c)
1520
d)
3040
16.
A solution calorimeter is used in two experiments to examine the endothermic reaction of ammonium nitrate with water. In the first experiment 10.0 g of NH4NO3 was added to 100.0 mL of water at 25°C in the calorimeter. In the second experiment 100.0 g of NH4NO3 was added to 100.0 mL of water at 25°C. The temperature of the second experiment compared with the first will
a)
Fall at the same rate to the same temperature
b)
Fall at the same rate to a lower temperature
c)
Fall at the faster rate to the same temperature
d)
Fall at the faster rate to a lower temperature
17.
The reaction between solutions of hydrochloric acid and sodium hydroxide can be represented by the following equation.
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l); ΔH=-56 kJ mol-1
60.0ml of 2.0M HCl, at 21oC, is mixed with 40.0mL of 2.0M NaOH, also at 21oC, in a well-insulated calorimeter. The calibration factor for the calorimeter and contents is 420 J K-1. The final temperature, in oC, of the resultant solution in the calorimeter would be closest to
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l); ΔH=-56 kJ mol-1
60.0ml of 2.0M HCl, at 21oC, is mixed with 40.0mL of 2.0M NaOH, also at 21oC, in a well-insulated calorimeter. The calibration factor for the calorimeter and contents is 420 J K-1. The final temperature, in oC, of the resultant solution in the calorimeter would be closest to
a)
11
b)
32
c)
37
d)
52
18.
A foam cup calorimeter containing 100mL of water is calibrated by passing an electric current through a small heater placed in the solution. Assuming that all measurements are accurate, which one of the following is the most likely calibration factor (in J oC-1) for the calorimeter and contents?
a)
120
b)
240
c)
480
d)
960
19.
Humans obtain all of their energy requirements from the food they eat. The amount of energy in food can be measured using a bomb calorimeter. The following are steps, in random order, that are taken to determine experimentally the energy content of a sample of a food, using a bomb calorimeter.
1. Measure the rise in temperature.
2. Fill the calorimeter with water and wait until the temperature has reached a steady value.
3. Accurately weigh the sample of the food and place it inside the sealed compartment or 'bomb' in the presence of excess oxygen.
4. Measure the rise in temperature again.
5. Pass a measured amount of electrical energy into the system.
6. Ignite the sample with electrical ignition wires.
Which one of the following alternatives best presents an appropriate sequence of procedures?
1. Measure the rise in temperature.
2. Fill the calorimeter with water and wait until the temperature has reached a steady value.
3. Accurately weigh the sample of the food and place it inside the sealed compartment or 'bomb' in the presence of excess oxygen.
4. Measure the rise in temperature again.
5. Pass a measured amount of electrical energy into the system.
6. Ignite the sample with electrical ignition wires.
Which one of the following alternatives best presents an appropriate sequence of procedures?
a)
5, 1, 3, 2, 4, 6
b)
2, 3, 1, 5, 6, 4
c)
3, 2, 5, 1, 6, 4
d)
3, 6, 1, 2, 5, 4
20.
A chemist used bomb calorimetry to measure the enthalpy change (ΔH) for the combustion of butane.
The calibration factor (CF) of the calorimeter was determined by measuring the temperature rise (ΔT1) that occurred when a known amount of charge (Q) was passed through the heating element in the calorimeter at a measured voltage (V). The CF, in JoC-1, is
The calibration factor (CF) of the calorimeter was determined by measuring the temperature rise (ΔT1) that occurred when a known amount of charge (Q) was passed through the heating element in the calorimeter at a measured voltage (V). The CF, in JoC-1, is
a)
Q/(VxΔT1)
b)
ΔT1/(QxV)
c)
VxQxΔT1
d)
(VxQ)/ΔT1
21.
A chemist used bomb calorimetry to measure the enthalpy change (ΔH) for the combustion of butane. In the calorimeter (calibration factor, CF), n mol of butane was then burnt and the resulting temperature rise (ΔT2) was measured.
The ΔH, in J mol-1, for the reaction
2C4H10(g)+13O2(g)→8CO2(g)+10H2O(g)
is
The ΔH, in J mol-1, for the reaction
2C4H10(g)+13O2(g)→8CO2(g)+10H2O(g)
is
a)
2 x CF x ΔT2 x n
b)
(2 x CF x ΔT2)/n
c)
(CF x ΔT2)/(2 x n)
d)
(CF x ΔT2)/n
22.
Bomb calorimeters may be calibrated by combusting a pure substance with a known heat of combustion. A particular bomb calorimeter was calibrated using 100mL of pure ethanol (density 0.789 g mL-1). If the temperature rose by 10.4oC during the combustion of pure ethanol, the calibration factor for the calorimeter would be
a)
131 kJ oC-1
b)
197 kJ oC-1
c)
226 kJ oC-1
d)
285 kJ oC-1
23.
For the reaction KOH(s) →KOH(aq); ΔH=-55.6 kJ mol-1, the temperature of water in the calorimeter is measured and then 1.00 g KOH is dissolved in the water. In order to return the calorimeter to the temperature it was prior to the addition of the KOH.
a)
991 J of energy must be supplied from outside the calorimeter
b)
991 kJ of energy must be removed from the calorimeter
c)
55.6 kJ of energy must be supplied from outside the calorimeter
d)
55.6 kJ of energy must be removed from the calorimeter
24.
In a calorimetry experiment, 50.0mL of 0.350M Fe3+(aq) was mixed with 50mL of 0.150M Sn2+(aq). The following chemical reaction occurred:
2Fe3+(aq)+Sn2+(aq)→2Fe2+(aq)+Sn4+(aq). The temperature rose by 0.730oC. Given that the calibration constant is 476 J oC-1, the magnitude of the heat of reaction (in kJ mol-1) is
2Fe3+(aq)+Sn2+(aq)→2Fe2+(aq)+Sn4+(aq). The temperature rose by 0.730oC. Given that the calibration constant is 476 J oC-1, the magnitude of the heat of reaction (in kJ mol-1) is
a)
19.9
b)
39.8
c)
46.3
d)
92.6
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