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WorksheetsAP Chemistry Unit 6 Review
Total questions: 25
Worksheet time: 50mins
Which of the following is an example of an endothermic reaction? (Select all that apply).
CH4 + 2 O2 → CO2 + 2 H2O
The energy of the system increases.
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
The energy of the surroundings increases.
An exothermic reaction increases the energy of the ____ and decreases the energy of the _____. (Separate answers by a comma and space).
(a)
This reaction is (a) .
Which of the following is/are true? Check all that apply.
Endothermic
Exothermic
-ΔH
Heat is lost to the surroundings.
The point of highest energy (noted with an arrow) on the energy diagram is the (a) .
ΔH for the reaction would be ____.
-
+
0
Not able to be determined using the given data.
Which of the following are true? Check all that apply.
Particles in a cooler body have a greater average kinetic energy than particles in a
warmer body.
Heat transfer/exchange occurs from collisions between particles in thermal contact.
Collisions stop after reaching thermal equilibrium.
When the average kinetic energy of two bodies at equilibrium is the same, their temperatures are the same too.
An 8.0 g sample of ice is melted. Which of the following is true of the enthalpy (ΔH) of the system?
The enthalpy has a positive sign because water gains energy to go from a solid to a liquid.
The enthalpy has a negative sign because water gains energy to go from a solid to a liquid.
The enthalpy has a positive sign because water loses energy to go from a solid to a liquid.
The enthalpy has a negative sign because water loses energy to go from a solid to a liquid.
When 1 mol of CH4 is combusted in air, 970 J of energy are evolved (released). What is the value of q in kJ for the reaction?
970 kJ
-970 kJ
0.970 kJ
-0.970 kJ
According to the first law of thermodynamics, energy is never created nor destroyed, but is (a) in chemical/physical processes.
What quantity of heat is required to raise a 5.0 mol sample of CO2(g) from 28 K to 43 K? (The specific heat capacity of CO2(g) is 0.839 J/g*K).
1200 J
2800 J
63 J
-2769 J
If a system is heated, which will occur? (Multiple answers may be right).
The energy of the system increases.
The surroundings will increase in energy.
The surroundings will be cooler.
The system will lose energy in order to create thermodynamic equilibrium.
If it takes 17.7 J to raise a 2.00 g sample of an unknown substance by 23.0°C, what is the identity of the substance?
Arsenic
H2O(g)
Copper
Oxygen
A student mixes 100. mL of 1.00 M H2CO3 (atomic mass 62.03 amu) and 100. mL of 1.00 M KOH (atomic mass 56.11 amu) in a calorimeter and notices that the temperature drops from 22.5°C to 19.5°C. Calculate the change in enthalpy. (The density of water is 1.00 g/mL and the specific heat capacity of water is 4.184 J/g°C).
1.26 kJ/mol
2.51 kJ/mol
-1.26 kJ/mol
-2.51 kJ/mol
The energy of the system increases in which of the following scenarios? Check all that apply.
Solid to liquid
Gas to liquid
Liquid to solid
Liquid to gas
Which of the following is true about the relationship between energy absorbed and released during phase changes? Check all that apply.
A substance's molar heat of condensation is equal to the negative of its molar heat of vaporization/evaporation.
A substance's molar heat of deposition is equivalent to its rate of sublimation.
The energy absorbed during melting is equal to the energy rebased from freezing.
The energy absorbed from sublimation is equal to the energy released from condensation.
A -ΔH value corresponds to a(n) ____ of heat energy while a +ΔH value corresponds to a(n) ____ of heat energy. (Pressure is constant).
absorbance; release
absorbance; reverse
release; absorbance
reverse; absorbance
For the reaction 4 NO3 + 2 H2O → 4 HNO3 + O2, using the average bond enthalpies, calculate the enthalpy of reaction.
N-O: 201 kJ/mol
N=O: 607 kJ/mol
O-H: 463 kJ/mol
O=O: 495 kJ/mol
495 kJ
-495 kJ
32 kJ
-32 kJ
The reaction 2 H2(g) + O2(g) → 2 H2O(g) releases 485 kJ of energy. What is the average bond enthalpy of an H-H bond?
O=O: 495 kJ/mol
O-H: 463 kJ/mol
436 kJ
-54.0 kJ
27.0 kJ
872 kJ
For the reaction 2 H2(g) + O2(g) → 2 H2O(l), what is the ΔH° of the reaction?
-483.6 kJ
-285.8 kJ
-241.8 kJ
-571.6 kJ
At the same temperature, calculate ΔH for the reaction 4 Al(s) + 3O2(g) → 2 Al2O3(s).
The ΔH°f of Al2O3 is -1669.8 kJ
1670 kJ
3340 kJ
-3340 kJ
-2815 kJ
How much energy must be added to a 41.0 g sample of ice at 0°C to change it to liquid water at 39°C? (The specific heat of water is 4.184 J/g*°C and the heat of fusion for ice is 334 J/g).
6,690 J
13,694 J
20,384 J
534,066 J
According to Hess's law, reversing a reaction reverses the ____ of ΔH.
sign
magnitude
both the sign and the magnitude
neither the sign nor the magnitude
Using Hess's law and the equations below calculate the enthalpy change for the reaction C + O2 → CO2.
C + 2 H2 → CH4 ΔH = W kJ
CH4 + 2 O2 → CO2 + 2 H2O ΔH = X kJ
2 H2O → 2 H2 + O2 ΔH = Y kJ
W+X+Y
W-X+Y
W+X-2Y
W+X
C(graphite) + O2(g) → CO2(g) ΔH = -393.5 kJ
4Al(s) + 3O2(g) → 2Al2O3(s) ΔH = -3339.6 kJ
2Al(s) + 9/2 O2(g) + 3C(graphite) → Al2(CO3)3(s) ΔH = -1553kJ
Calculate the enthalpy change for the reaction Al2(CO3)3(s) → Al2O3(s) + 3 CO2(g).
-1297.3 kJ
-510.3 kJ
-2967.1 kJ
1063.7 kJ
