How would you distinguish a second-order reaction in one reactant from a second-order reaction in two different reactants?

• A. If rate = k [A]^2 that's two reactants; If rate = k [A][B] that's one reactant
• B. If rate = k [A]^2; vary [A] to get exponent 2; If rate = k [A][B]; vary [A] and [B] independently to find exponents
• C. Check temperature
• D. Look at units of k

Answer: (B)