1. The problem statement, all variables and given/known data The second order reaction 2Mn(CO)sub5 → Mnsub2 (CO)sub10 has a rate constant equal to 3.0 *10^9 M^-1s^-1 at 25oC. If the initial concentration for Mn(CO)sub5 is 1.0 * 10^-5 M, how long will it take for 90% of the reactant to disappear? 2. Relevant equations Rate Law = k*[Mn(CO)sub5] 3. The attempt at a solution Not sure what they want me to do here? If its a half life thing I understand, but it is not stated anywhere in the problem and I assume we're not expected to know such things. I can find the rate most certainly, and the units would be what they are, but how exactly do I relate such things in an equation to find how long it would take for 90% of the reaction to disappear? Can someone point me in the right direction? I have work for the day so I won't have as much time as I'd like to work it out, but if someone could just give me a nudge I'd be fine! Thanks.