7B.9

[RRahimtoola1I]

How do you do this problem or other problems similar to this when they give you only the initial concentration of the reactant and then a later concentration of a product?

For the first-order reaction A > 3B + C, when initial concentration of A = 0.015 mol/L, the concentration of B increases to 0.018 mol/L in 3.0 min. (a) What is the rate constant for the reaction expressed as the rate of loss of A? (b) How much more time would be needed for the concentration of B to increase to 0.030 mol/L?

[Adam Kramer 1A]

You know that B increased . 018M in 3 minutes, so A decreased by 0.06M in the same time. You can then calculate the rate and you know it's first order, so you can then plug in the variables into the rate law equation and solve for the k rate constant.