Question

does background radiation affect rate constant and impact the order of the reaction? so if the background radiation was recorded as a large number would it affect the rate constant and order of the reaction in an experiment?

Answer 1

The rate constant of a reaction is is given by the expression k=k₀exp(-Ea/RT),(Arhenius Equation) where Ea is the activation energy of the reaction and R is universal gas constant and T is the temperature of the reaction vessel.Also the order of a reaction is always fixed and is derived experimentally by performing the rate versus concentration change analysis of the reactant.

Now if we observe the rate constant of reaction is dependent only on temperature since the activation energy is generally independent of temperature and R is constant.So if the reaction is conducted at room temperature or lesser temperature then background radiation will not affect the rate constant.But if the reaction is conducted in a room of higher temperature usully T>1000K then the background radiation may affect the rate.This is because the background radiation will have certain emmisive power and the reaction vessel will have certain absorbtivity and based on these interactions it is quite possible that the reaction temperature may increase the desired temperature and thus the rate constant of reaction will change from the Arhenius equation.

Now,when it comes to order of the reaction ,it is also determined by changing the concentration of species participating in the reaction and by changing the temperature as well.So when we will conduct the experiment,at different temperatures,definitely the rate of reaction as well as rate constant both will change because of the background radiation which will have direct effect on the temperature of reaction vessel.In the case of an elementary step, the order is always equal to the number of reactant particles, so it doesn't depend on temperature and thus background radiation will not affect order for single reactant or elementary step.But,At low temperatures, one term may dominate, while at high temperatures, another might, leading to an apparently change in the approximate overall order of the reaction.So in that case the background radiation can affect the overall order of the reaction.

So the overall conclusion is that Background radiation may affect the order as well as rate constant of the reaction by changing the effective temperature of the reaction vessel.