The rate law for the decomposition of phosphine (PH3) is below.It takes 120. s for 1.00 M PH3 to decrease to 0.250 M. How much time is required for 4.00 M PH3 to decrease to a concentration of 0.315 M?The post The rate law for the decomposition of phosphine (PH3) is below. It takes 120. s for 1.00 M PH3 to decrease to 0.250 M. How much time is required for… first appeared on Nursing School Essays.