To determine the overall order from the rate law, you sum the exponents and then...

To determine the overall order from the rate law, you sum the exponents and then...

• A. Take the sign of the sum
• B. Take the absolute value of the sum
• C. Multiply the exponents
• D. Ignore the exponents

Answer: (B)

The key idea is that the overall order of a reaction is found by summing the exponents on the concentration terms in the rate law. Those exponents tell you how the rate scales with each reactant, and adding them gives you a single number that describes the combined dependence on all concentrations. To express the overall order as a nonnegative quantity (which is how we usually report order), you take the absolute value of that sum. This ensures the rate’s dependence is described by a nonnegative magnitude, even if some terms would give a negative exponent in more unusual cases. The other options don’t fit: taking the sign would imply a negative order could be meaningful; multiplying the exponents is not how the rate scales with concentration; ignoring the exponents would miss the very way the rate depends on each reactant.

The key idea is that the overall order of a reaction is found by summing the exponents on the concentration terms in the rate law. Those exponents tell you how the rate scales with each reactant, and adding them gives you a single number that describes the combined dependence on all concentrations. To express the overall order as a nonnegative quantity (which is how we usually report order), you take the absolute value of that sum. This ensures the rate’s dependence is described by a nonnegative magnitude, even if some terms would give a negative exponent in more unusual cases. The other options don’t fit: taking the sign would imply a negative order could be meaningful; multiplying the exponents is not how the rate scales with concentration; ignoring the exponents would miss the very way the rate depends on each reactant.