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For a reaction involving species x, y and z, which of the following rate laws has an overall order of 0.5?

1. Rate = k [Cx] [Cy] [Cz]
2. Rate = k [Cx]⁰.5 [Cy]⁰.5 [Cz]⁰.5
3. Rate = k [Cx]¹.5 [Cy]⁻¹ [Cz]⁰
4. Rate = k [Cx][Cz]⁰ / [Cy]²

Correct answer: Rate = k [Cx]¹.5 [Cy]⁻¹ [Cz]⁰

Solution

Overall order is the algebraic sum of exponents: option with 1.5 + (-1) + 0 = 0.5 is correct.

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