For a reaction A gives products, doubling the concentration of A leaves the rate unchanged. The reaction is
- A. first order in A
- B. second order in A
- C. third order in A
- D. zero order in A
Explanation
If concentration has no effect on rate then the exponent of that term must be zero, since anything raised to the power zero equals one. Had the rate doubled the reaction would be first order, and had it quadrupled it would be second order, which is the reasoning used to find orders experimentally. Zero order behaviour usually signals a saturated catalyst or enzyme.