AP Chemistry : AP Chemistry

Study concepts, example questions & explanations for AP Chemistry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #4 : Net Ionic Equations

What is the net ionic reaction when a solution of Cd(NO3)2 is reacted with (NH4)2S?

Possible Answers:

Cd(NO3)2 (aq) + (NH4)2S (aq) ->  CdS (aq) + 2 NH4NO3 (aq)

Cd2+(aq) + S2- ->  CdS (s)

NH4+ (aq) + NO3- (aq)  ->  NH4NO3 (s)

Cd(NO3)2 (aq) + (NH4)2S (aq) ->  CdS (s) + 2 NH4NO3 (aq)

Cd(NO3)2 (aq) + (NH4)2S (aq) ->  CdS (s) + 2 NH4NO3 (aq)

Correct answer:

Cd2+(aq) + S2- ->  CdS (s)

Explanation:

Only Cd and S ions are interacting according to the solubility rules to form a solid precipitant.

Example Question #5 : Net Ionic Equations

What is the net ionic reaction when a solution of rubidium sulfate is mixed with barium hydroxide?

Possible Answers:

No Reaction

Rb+ (aq) + OH- (aq)  ->  RbOH (s)

Rb2SO4 (aq) + Ba(OH)2 (aq)  ->  2 RbOH  (aq)  +  BaSO4 (s)

Ba2+ (aq) + SO42- (aq)  ->  BaSO4 (s)

Rb2SO4 (aq) + Ba(OH)2 (aq)  ->  2 RbOH  (s)  +  BaSO4 (aq)

Correct answer:

Ba2+ (aq) + SO42- (aq)  ->  BaSO4 (s)

Explanation:

Only the Ba and sulfate ions will react according to the solubility rules.

Example Question #41 : Kinetics And Energy

The rate constant for a second-order reaction is 0.15 M-1s-1.  If the initial concentration of the reactant is 0.30 M, how long does it take for the concentration to decrease to 0.15 M?

Possible Answers:

11.1 seconds

22.2 seconds

88.8 seconds

253 second

44.4 second

Correct answer:

22.2 seconds

Explanation:

 

Example Question #1 : Integrated Rate Laws

02

Based on the figure above, what is the order of reaction?

Possible Answers:

First order

Third Order

Zero Order

Second Order

Squared Order

Correct answer:

First order

Explanation:

For a first order reaction, the ln [A]t is linear with t.

Example Question #1 : Integrated Rate Laws

A compound decomposes by a first-order process.  If 25.0% of the compound decomposes in 60 minutes, the half-life of the compound is?

Possible Answers:

198 minutes

120 minutes

65 minutes

145 minutes

180 minutes

Correct answer:

145 minutes

Explanation:

 

 

Example Question #2 : Integrated Rate Laws

Cyclopentane is unstable and decomposes by a first order reaction.  The rate constant for this reaction is 9.5 s-1.  What is the half life of the reaction?

Possible Answers:

0.132 seconds

0.0314 seconds

0.0582 seconds

0.0729 second

0.0614 seconds

Correct answer:

0.0729 second

Explanation:

Example Question #3 : Integrated Rate Laws

The half life of a first order reaction is 1.5 hours.  What is the rate constant of this reaction?

Possible Answers:

0.52

0.21

0.46

0.75

1.5

Correct answer:

0.46

Explanation:

 

Example Question #641 : Ap Chemistry

Which of the following is true?

Possible Answers:

The rate-determining step of a reaction is the rate of the slowest elementary step of its mechanism

All of the above

Since intermediate compounds can be formed, the chemical equations for the elementary reaction in a multistep mechanism do not always have to add to give the chemical equation of the overall process.

In a reaction mechanism an intermediate is identical to an activated complex

If we know that a reaction is an elementary reaction, then we know its rate law.

Correct answer:

All of the above

Explanation:

All of the above describe elementary reactions and how they give an overall mechanism.

Example Question #2 : Reaction Mechanisms

A possible mechanism for the overall reaction Br2 (g) + 2 NO (g)  ->  2 NOBr(g) is 

02

The rate law for the formation of NOBr based on this mechanism is rate =           .

Possible Answers:

Correct answer:

Explanation:

Based on the slowest step the rate law would be:  Rate = k2 [NOBr2] [NO], but one cannot have a rate law in terms of an intermediate (NOBr2).

 

Because the first reaction is at equilibrium the rate in the forward direction is equal to that in the reverse, thus:

 

  and:  

 

Substitution yields:  

Example Question #642 : Ap Chemistry

For the reaction NO2 (g) + CO (g) -> NO (g) + CO2 (g), the reaction was experimentally determined to be Rate = k[NO2]2.  If the reaction has the following mechanism, what is the rate limiting step, and why?

 

Step 1:  2 NO2  -> NO3 + NO                            (slow)

Step 2:  NO3 + CO -> NO2 + CO2                     (fast)

Possible Answers:

Step 2 is limiting because the NO3 intermediate has to be formed before the reaction can occur.

Step 2 is limiting because the fast step determines how quickly the reaction can occur.

Step 1 is limiting because the NO2 is a reactant.

Step 1 is limiting because the reaction can not go faster than its slowest step.

Not enough information

Correct answer:

Step 1 is limiting because the reaction can not go faster than its slowest step.

Explanation:

The reaction can never go faster than its slowest step. 

Learning Tools by Varsity Tutors