AP Chem Semester 01 Exam Review Units 04-06

Multiple Choice

Based on the information above, what is the standard enthalpy change for the following reaction?

N₂H₄(l) + H₂(g) → 2NH₃(g)

• -151kJ/mol_rxn

• -935kJ/mol_rxn

• -1119kJ/mol_rxn

• -59kJ/mol_rxn

Multiple Choice

2Al(s) + Fe₂O₃(s) → 2Fe(s) + Al₂O₃(s)

ΔH_rxn = -860kJ/mol_rxn

Based on the standard enthalpies of formation ΔH^∘_f provided in the table, what is the approximate ΔH^∘_f for Fe₂O₃(s) ?

• +2540kJ/mol

• −2540kJ/mol

• +820kJ/mol

• −820kJ/mol

Multiple Choice

Use the bond energies provided to estimate ΔH°_rxn for the reaction below.
XeF₂ + 2 F₂  → XeF₆        
 ΔH°_rxn = ?
NO calculator! 

• -270 kJ
• +176 kJ
• -660 kJ
• +159 kJ

Multiple Choice

Carbon monoxide reacts with oxygen to form carbon dioxide by the following reaction:

2 CO(g) + O₂(g) → 2 CO₂(g) ΔH = -302.4 kJ/mol

What is the expected energy change for the reaction of three moles of O₂ with four moles of CO?

• -302.4 kJ/mol

• -604.8 kJ/mol

• -907.2 kJ/mol

• -151.2 kJ/mol

Multiple Choice

A 100mL sample of water is placed in a coffee cup calorimeter.  Solid NaCl is then dissolved in the water.  The temperature of the water decreases from 20.5°C to 19.7°C and is then allowed to return to room temperature (20.5°C).  Determine the signs for ΔH and ΔS for the process of dissolving NaCl and 
ΔG for the entire process at constant temperature.
NO Calculator!

• +ΔH, −ΔS, ΔG=0

• −H, +S, ΔG=0

• +ΔH, +ΔS, −ΔG

• −ΔH, −ΔS, −ΔG

Multiple Choice

2C(s) + 2H₂(g) → C₂H₄(g) ΔH⁰_rxn = +52.4 kJ/mol_rxn

It is observed that the reaction producing C₂H₄(g) from its elements goes essentially to completion. Which of the following is a true statement about the thermodynamic favorability of the reaction?

• The reaction is unfavorable due to both enthalpy and entropy changes.

• The reaction is favorable and driven by an entropy change only.

• The reaction is favorable and driven by an enthalpy change only.

• The reaction is favorable and driven by both enthalpy and entropy changes.

Multiple Choice

Calculate the standard entropy change for the industrial synthesis of urea (a common fertilizer):
CO₂(g) + 2 NH₃(g) → CO(NH₂)₂(s) + H₂O(ℓ)
at 25◦C the thermodynamic data shown is applicable. 
YES Calculator!

• −424.13 J/mol⋅K

• −212.07 J/mol⋅K

• −848.26 J/mol⋅K

• −1696.52 J/mol⋅K

Multiple Choice

Which of the following would probably have a positive ∆S value?
NO Calculator!

• 2 Ag(s) + Br2(ℓ) → 2 AgBr(s)

• H₂(g) + I₂(s) → 2 HI(g) 

• 2 NO₂(g) → N₂O₄(g)

• He(g, 2 atm) → He(g, 10 atm)

Multiple Choice

Which of the following sets of conditions must be true for a reaction that is thermodynamically favorable only at relatively high temperatures?

• -ΔG

  -ΔH

  -ΔS

• -ΔG

  +ΔH

  +ΔS

• +ΔG

  -ΔH

  -ΔS

• +ΔG

  +ΔH

  +ΔS

Multiple Choice

An increase in temperature will increase the rate of

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• an ENDOthermic reaction ONLY

• an EXOthermic reaction ONLY

• BOTH ENDOthermic and EXOthermic reactions

• NEITHER ENDOthermic nor EXOthermic reactions

Multiple Choice

In the reaction,

NO + O₃ → NO₂ + O₂

the N atom in the NO molecule must strike a terminal O atom in the O₃ molecule. Which of the diagrams below would most likely result in the formation of the products?

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Multiple Select

A kinetics experiment is set up to measure the rate of the combustion of organic material (wood) with oxygen gas, O₂, by measuring the volume of carbon dioxide gas, CO₂, generated at 25°C and 1 atm as a function of time.

In general, which does NOT increase the rate of reaction?

Select ALL that apply

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• increasing the activation energy

• increasing the temperature of the reaction

• increasing the particle size by using a large block of wood instead of fine particles of sawdust

• increasing the concentration of oxygen reacting with the organic material

Multiple Choice

A student collects the following kinetics data for a reaction.  Based on the data, how would you classify the reaction? Why?

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• First Order.

  Concentration is halved after 3.00 min and again after another 3.00min. Thus the half-life of the reaction is constant, so the reaction is first order.

• Zero Order.

  Concentration is halved after 3.00 min and again after another 3.00min. Thus the half-life of the reaction is constant, so the reaction is zero order.

• Second Order.

  Concentration is halved after 3.00 min and again after another 3.00min. Thus the half-life of the reaction is constant, so the reaction is second order.

• First Order.

  ln(Concentration) is halved after 3.00 min and again after another 3.00min. Thus the half-life of the reaction is constant, so the reaction is first order.

Multiple Choice

The reaction pathways below represent the same reaction at the same temperature. Which represents the reaction in the presence of a catalyst?

Multiple Choice

Which of the following is a graph that describes the pathway of reaction that is exothermic and has a large activation energy?

Multiple Select

What must reactant particles achieve before a collision will be successful?

SELECT ALL THAT APPLY

• Collide with enough energy that meets or exceeds the minimum activation energy.

• Collide with the correct orientation.

• Collide in a solution with at least the standard concentration.

• Collide in the gas or aqueous phase, but not the solid or liquid phase.