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    2021 Kinetics MCQ Quiz - Worked Solns

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    This document is a 5 question multiple choice quiz on reaction kinetics for a Junior College Chemistry class. 1) The first question asks about radioactive decay of Iodine-131 and calculates that after 10 half lives, 1/1024 or approximately 0.1% of the original isotope would remain. 2) The second question involves rate data from an experiment and determines that the missing value in the table is 50 based on the reaction orders. 3) The third question analyzes a proposed reaction mechanism and identifies the correct rate equation. 4) The fourth question examines an energy profile diagram and identifies which value corresponds to the enthalpy change of the reaction. 5) The fifth question considers

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    2021 Kinetics MCQ Quiz - Worked Solns

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    This document is a 5 question multiple choice quiz on reaction kinetics for a Junior College Chemistry class. 1) The first question asks about radioactive decay of Iodine-131 and calculates that after 10 half lives, 1/1024 or approximately 0.1% of the original isotope would remain. 2) The second question involves rate data from an experiment and determines that the missing value in the table is 50 based on the reaction orders. 3) The third question analyzes a proposed reaction mechanism and identifies the correct rate equation. 4) The fourth question examines an energy profile diagram and identifies which value corresponds to the enthalpy change of the reaction. 5) The fifth question considers

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    2021 Kinetics MCQ quiz_worked Solns

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    This document is a 5 question multiple choice quiz on reaction kinetics for a Junior College Chemistry class. 1) The first question asks about radioactive decay of Iodine-131 and calculates that after 10 half lives, 1/1024 or approximately 0.1% of the original isotope would remain. 2) The second question involves rate data from an experiment and determines that the missing value in the table is 50 based on the reaction orders. 3) The third question analyzes a proposed reaction mechanism and identifies the correct rate equation. 4) The fourth question examines an energy profile diagram and identifies which value corresponds to the enthalpy change of the reaction. 5) The fifth question considers

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    65 views3 pages

    2021 Kinetics MCQ Quiz - Worked Solns

    Uploaded by

    PROgamer GT
    This document is a 5 question multiple choice quiz on reaction kinetics for a Junior College Chemistry class. 1) The first question asks about radioactive decay of Iodine-131 and calculates that after 10 half lives, 1/1024 or approximately 0.1% of the original isotope would remain. 2) The second question involves rate data from an experiment and determines that the missing value in the table is 50 based on the reaction orders. 3) The third question analyzes a proposed reaction mechanism and identifies the correct rate equation. 4) The fourth question examines an energy profile diagram and identifies which value corresponds to the enthalpy change of the reaction. 5) The fifth question considers

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    © All Rights Reserved
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    of 3

    JURONG PIONEER JUNIOR COLLEGE

    2021 JC1 H2 CHEMISTRY MCQ CLASS QUIZ


    (Reaction Kinetics)
    Name:__________________________________ Class: 21S____

    Duration: 10 minutes Total Marks:

    5
    For each question there are four possible answers, A, B, C and D. Choose the one you consider
    to be correct and indicate your answers in the brackets provided.

    1. Iodine-131 is a radioactive isotope with a half-life of 8 days. Following the nuclear power
    plant disaster at Chernobyl in 1986, it was stated that a cloud of vapour containing
    iodine-131 was formed which would not be safe for 80 days.  10 half-lives
    Given that radioactive decay is a first-order reaction (constant half-life), what fraction of
    the isotope would remain after that time?
    10
     1
    After 10 half-lives, fraction of reactant left =  
    2

    1 1 1 D 1
    A B C
    20 160 28 210
    ( D )

    . The table shows experimental results obtained for the rate of the following reaction.
    2XO + O2  2XO2 Expt 1 Expt 2 Expt 3 Expt 4

    (partial pressure of XO)1 (in arbitrary units) 100 100 50 25


    2x

    (partial pressure of O2)1 (in arbitrary units) 100 25 100


    2x
    ?

    relative rate 1.0 0.25 0.50 0.125


    4x
    What is the missing value of the partial pressure of O2 in the table?
    Comparing expt 1 and 2:
    When PO increases to 4 times, rate also increases to 4 times.
    2

     order of reaction w.r.t PO is 1.


    2

    Comparing expt 1 and 3:


    When PXO doubles, rate also doubles.
     order of reaction w.r.t PXO is 1.

    Comparing expt 3 and 4:


    When PXO doubles, rate increases to 4 times  PO must have doubled.
    2

    So, PO in experiment 4 is 50.


    2

    A 12.5 B 25 C 50 D 100
    ( C )

    2021 JPJC J1 H2 Chemistry (9729) 1


    3. The mechanism for the production of nitrosyl bromide, NOBr, from nitrogen monoxide and
    bromine is thought to be as follows.
    NO + Br2 ⇌ NOBr2 (fast)
    NOBr2 + NO ⟶ 2NOBr (slow)
    Which of the following rate equations is consistent with the mechanism?
    From the slow step, rate = k’ [NOBr2] [NO].
    However, NOBr2 is an intermediate, so should not be in the final rate equation.
    From the fast step, [NOBr2]  [NO][Br2]
    Hence, rate = k’ [NOBr2] [NO]
    = k [NO][Br] [NO]
    = k [NO]2 [Br]

    A rate = k [NOBr2] [NO]


    B rate = k [NO] [Br2]
    C rate = k [NO]2 [Br2]
    D rate = k [NO] [Br2]2
    ( C )

    4. Which of the following statements is true about the energy profile below?

    Energy F

    E4
    E3

    reactants E1
    X

    H
    E2
    products

    Extent of reaction
    A F is the intermediate formed.
    X is the intermediate, not F. F is the activated complex in the transition
    state.
    B The enthalpy change of the reaction is E3 – E2.
    True. H is the difference in energy of the reactants and products. Since
    the products has a lower energy, H < 0 (exothermic reaction).
    C The first step is the slow step in the mechanism.
    Ea for step 1 is E1. Ea for step 2 is E4. E4 > E1  step 2 is the slow step.
    D E2 corresponds to the activation energy for the reaction in the second step.
    Should be E4. E2 is the Ea of the first step of the reverse reaction.
    ( B )

    2021 JPJC J1 H2 Chemistry (9729) 2


    5. The diagram represents the Boltzmann distribution of molecular energies at a given
    temperature.

    Number of T2 > T1
    molecules
    T1
    T2

    Area left unshaded


    is smaller
     shaded area is
    greater at T2 0 E1 energy E2

    As the temperature increases, which statements are correct?

    1 The maximum of the curve is displaced to the right.


    True. As T, the average kinetic energies of the molecules increases.
    (See curve at T2)  As the area under the curve is constant, the maximum is
    displaced downward and to the right.

    2 The proportion of molecules with energies above any given value increases.
    True. e.g. E1 or E2, the area under the curve to the right for T2 curve is
    always larger than the area under the curve to the right for T1 curve.

    3 The proportion of molecules with any given energy increases.


    False. e.g. proportion of molecules with energy E1 is lower at T2 than at T1.
    (See red dots on the curve)

    A Only 1 is correct.
    B 1 and 2 are correct.
    C 2 and 3 are correct.
    D 1, 2 and 3 are correct.
    ( B )

    2021 JPJC J1 H2 Chemistry (9729) 3

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