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AP Chemistry Kinetics — practice questions

Explore 15 free Kinetics questions in AP Chemistry Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Kinetics questions and exercises with answers

Showing questions 1–15 of 15.

What name is given to the instantaneous rate of a reaction at the moment the reaction commences?Read the answer and worked solution →Rates of reactions involving aqueous electrolytes are conveniently followed by measuring which property?Read the answer and worked solution →In the reaction 5Br- + BrO3- + 6H+ giving 3Br2 + 3H2O, bromide ion is disappearing at 3.5 x 10^-4 M/s at some moment. At what rate is Br2 appearing?Read the answer and worked solution →A rate constant is reported in units of L/mol/s. What is the overall order of its reaction?Read the answer and worked solution →N2O5 dissolved in chloroform decomposes by a first order path with k = 6.2 x 10^-4 per minute. What is the rate when [N2O5] = 0.40 M?Read the answer and worked solution →Iodine-131 decays to xenon-131 by a first order process with a rate constant of 0.138 per day. How many days does it take for 90% of a sample to decay?Read the answer and worked solution →Ozone decomposes by the two step mechanism O3 giving O2 + O, then O + O3 giving 2O2. Which species is an intermediate?Read the answer and worked solution →As a simple second order reaction proceeds, what happens to its half-life?Read the answer and worked solution →A first order reaction has a half-life of 8.50 min. Starting from 0.150 mol/L, how long until the concentration falls to 0.0300 mol/L?Read the answer and worked solution →Nitric oxide reacting with chlorine, 2NO + Cl2 giving 2NOCl, appears to occur as an elementary termolecular step. What rate law follows from that step?Read the answer and worked solution →Which metal catalyses the hydrogenation of polyunsaturated fats and oils into saturated ones?Read the answer and worked solution →Which enzyme model pictures the active site as flexible, changing shape to bind its substrate?Read the answer and worked solution →What forms when a substrate binds at an enzyme's active site during catalysis?Read the answer and worked solution →Balance the ammonia burnRead the answer and worked solution →Sort the rate moversRead the answer and worked solution →

Worked practice questions

What name is given to the instantaneous rate of a reaction at the moment the reaction commences?

  1. The average rate of the reaction
  2. The initial rate of the reaction
  3. The integrated rate of the reaction
  4. The terminal rate of the reaction
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Correct answer: B. The initial rate of the reaction

1. An instantaneous rate is the rate at one specific moment, read from the tangent to the concentration curve. 2. Taken at the very start of the reaction, that instantaneous rate is called the initial rate. 3. The average rate instead spans a whole time interval, so it is not tied to the starting instant. _Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.1 Chemical Reaction Rates_

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Rates of reactions involving aqueous electrolytes are conveniently followed by measuring which property?

  1. A change in the solution's conductivity
  2. A change in the solution's colour depth
  3. A change in the reaction vessel pressure
  4. A change in the total solution volume
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Correct answer: A. A change in the solution's conductivity

1. Electrolytes carry current, so their concentrations set how well the solution conducts. 2. As an electrolyte is consumed or produced, the conductivity shifts, and that shift tracks the rate. 3. Colour absorption suits coloured substances and pressure suits gases, not dissolved ions as such. _Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.1 Chemical Reaction Rates_

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In the reaction 5Br- + BrO3- + 6H+ giving 3Br2 + 3H2O, bromide ion is disappearing at 3.5 x 10^-4 M/s at some moment. At what rate is Br2 appearing?

  1. 5.8 x 10^-4 M/s
  2. 3.5 x 10^-4 M/s
  3. 1.2 x 10^-4 M/s
  4. 2.1 x 10^-4 M/s
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Correct answer: D. 2.1 x 10^-4 M/s

1. Rates of different species are linked through the stoichiometric coefficients of the balanced equation. 2. Five bromide ions are consumed for every three Br2 molecules formed. 3. So the Br2 rate is 3/5 of the bromide rate. 4. Substituting gives 3/5 x 3.5 x 10^-4 mol per litre per second. 5. The product is 2.1 x 10^-4 M/s of Br2 appearing. 6. Sanity check: fewer Br2 form than Br- vanish, so the answer must be smaller than 3.5 x 10^-4 M/s. 7. The value 5.8 x 10^-4 M/s applies the factor 5/3 the wrong way round. 8. The value 3.5 x 10^-4 M/s assumes every species changes at the same rate, ignoring the coefficients. _Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.1 Chemical Reaction Rates_

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More Chemistry topics

Composition of Substances and SolutionsEquilibria of Other Reaction ClassesSolutions and ColloidsStoichiometry of Chemical ReactionsThermodynamicsAcid-Base EquilibriaAtoms, Molecules, and IonsChemical Bonding and Molecular Geometry