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1 August, 08:28

A certain reaction X + Y → Z is described as being first order in [X] and third order overall. Which of the following statements is or are true?: The rate law for the reaction is: Rate = k[X][Y]2. If the concentration of X is increased by a factor of 1.5, the rate will increase by a factor of 2.25. If the concentration of Y is increased by a factor of 1.5, the rate will increase by a factor of 2.25.

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Answers (2)
  1. 1 August, 08:37
    0
    a) True

    b) False

    c) True

    Explanation:

    The order of reactants decides the exponents of respective reactant concentrations.

    Since X is first order, exponent is = 1

    Overall third order, Exponent X + Exponent Y = 3

    Hence, exponent Y = 2.

    Hence,

    Rate = k[X][Y]^2

    b)

    If X conc is increased by 1.5 Rate should increase by 1.5 because k proportional to [X]. Hence, statement is False

    c)

    If Y conc is increased by 1.5 Rate should increase by 2.25 because k proportional to [Y]^2 = (1.5) ^2 = 2.25. Hence, statement is True
  2. 1 August, 08:43
    0
    The second statement is true: If the concentration of Y is increased by a factor of 1.5, the rate will increase by a factor of 2.25.

    Explanation:

    Hi there!

    Let's write the rate law for the original reaction and the reaction with X increased by 1.5:

    rate 1 = k [X][Y]²

    rate 2 = k[1.5 X][Y]²

    Now we have to demonstrate if rate 2 = 2.25 rate 1

    Let's do the cocient between the two rates:

    rate 2 / rate 1

    if rate 2 = 2.25 rate 1

    Then,

    rate 2 / rate 1 = 2.25 rate 1 / rate 1 = 2.25

    Let's see if this is true using the expressions for the rate law:

    rate 2 / rate 1

    k[1.5 X][Y]² / k [X][Y]² = 1.5 k [X][Y]² / k[X][Y]² = 1.5

    2.25 ≠ 1.5

    Then the first statement is false.

    Now let's write the two expressions of the rate law, but this time Y will be increased by 1.5:

    rate 1 = k[X][Y]²

    rate 2 = k[X][1.5Y]²

    Again let's divide both expressions to see if the result is 2.25

    rate 2 / rate 1

    k[X][1.5Y]² / k [X][Y]²

    (distributing the exponent)

    (1.5) ²k [X][Y]² / k [X][Y]² = (1.5) ² = 2.25

    Then the second statement is true!
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