1. The problem statement, all variables and given/known data I don' t want to be too specific, but it's basically "A + B -> C has the rate law Rate=k[A][ B], How long does it take [A] to reach concentration X. K is given and the initial concentrations of A and B are given." 2. Relevant equations The integrated rate laws, whether I need first or second or is one of the things that's confusing me. 3. The attempt at a solution I know this is simple but I'm quite confused :/ The reaction is first order with A, so I'm tempted to use the given value of A and the integrated rate law for first order reactions. But then doesn't the concentration of B effect the rate? If I need to take this into account I'm confused as to how I should proceed. I don't want to much info but some intuition would be great. Thanks!