Rate Equations and Orders of Reaction · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The Data Decides the Order

Science · Chemistry · ages 17-18
Name ______________________   Date ____________

  1. The orders in A and B are 1 and 2. What is the overall order?

    • 2, the largest single order
    • 3, the sum of the orders
    • 1, the smallest single order

  2. What is the general form of a rate equation?

    • Rate equals k times each concentration raised to its order
    • Rate equals the balanced equation coefficients added up
    • Rate equals temperature times pressure

  3. Doubling A doubles the rate, with all else fixed. What is the order in A?

    • Zero
    • Second
    • First

  4. Doubling C leaves the rate unchanged. The order in C is zero. This claim is true.

    Circle one:   True   False

  5. Doubling B quadruples the rate, with all else fixed. What is the order in B?

    • Second
    • First
    • Zero

  6. C appears in the balanced equation but doubling C never changes the rate. How is that possible?

    • Every species in the equation is always first order
    • C reacts after the slow step or sits in huge excess
    • The rate constant k cancels C out

  7. The runs give rate equals k times A. What are the units of k?

    • Moles per decimetre cubed per second
    • Per second
    • Decimetres cubed per mole per second

  8. Runs show doubling A doubles the rate while doubling B leaves it flat. What is the rate equation?

    • Rate equals k times A times B
    • Rate equals k times A
    • Rate equals k times B squared
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The Data Decides the Order W1-mt_1x3ogDKGxC-s1

  1. 3, the sum of the orders · Overall order is the sum of the individual orders: 1 + 2 = 3.
  2. Rate equals k times each concentration raised to its order · Each reactant concentration is raised to its measured order and multiplied by k.
  3. First · Rate tracking concentration one to one means first order.
  4. True · No change in rate when C changes means C does not affect the rate: order zero.
  5. Second · Two squared is four, so the rate follows the square of B: second order.
  6. C reacts after the slow step or sits in huge excess · Rate follows the slow step, so latecomers or flooded reactants can be order zero.
  7. Per second · The equation is first order overall, and first order k has units of per second.
  8. Rate equals k times A · A is first order and B is zero order, so B drops out and rate equals k times A.
Worksheet · LightMySky