Simple calculation (examples) For the reaction A - products the first order rate constant is 4.5 x 10-25-1. Calculate the length of time it takes for [A] to decrease to one eighth its original value. A second order reaction has a half-life of 450 s, with an initial concentration of 7.5 x 10 4 mol cm-3. What is the rate constant for the reaction? The vapour pressure of benzene in the range 042 C can be expressed in the form: 1785 K - 7.0871 kPa T Estimate the temperature (in K) at a corresponding pressure of 10 kPa