Determine Rate Law: Initial Rates

Question

The following initial rate data are for the oxidation of arsenate ion by cerium(IV) ion in aqueous solution:

AsO₃^3- + 2 Ce⁴⁺ + H₂OAsO₄^3- + 2 Ce³⁺ + 2 H⁺

Experiment	[AsO33-]o, M	[Ce4+]o, M	Initial Rate, M s-1
1	4.62×10-2	0.593	8.43×10-3
2	9.24×10-2	0.593	1.69×10-2
3	4.62×10-2	1.19	3.40×10-2
4	9.24×10-2	1.19	6.79×10-2

Complete the rate law for this reaction in the box below.

Use the form k[A]^m[B]ⁿ , where '1' is understood for m or n and concentrations taken to the zero power do not appear. Don't enter 1 for m or n.

Rate =

From these data, the rate constant is _____M^-2s^-1.

Answer 1

Rate =  k [AsO33-] [Ce4+]2

rate constant is _0.52____M^-2s^-1.

Explanation: When the Ce⁴⁺ concentration is kept constant and the AsO₃^3- concentration doubles, the rate doubles, indicating a first order relationship for AsO₃^3-.

when the AsO₃^3- concentration is kept constant, and the Ce⁴⁺ concentration is doubled, the rate increased by a factor of 4, indicating a second order dependence on Ce⁴⁺ concentration.