Question

$ 2B{r^ - }{\text{ }} + {\text{ }}{H_2}{O_2}{\text{ }} + {\text{ }}2{H^ + } \to {\text{ }}B{r_2}{\text{ }} + {\text{ }}2{H_2}O $ Rate = $ k{\text{ }}\left( {{H_2}{O_2}} \right)\left( {{H^ + }} \right)\left( {B{r^ - }} \right) $ what is the effect on rate constant on increasing bromide ion?

Answer 1

Hint : Rate of a reaction is the speed at which the reaction takes place. In simple words how quickly the product is formed in a reaction. It is expressed in terms of concentration.
Rate constant expresses the relationship between the rate of reaction and the concentration of the reaction substance.

Complete Step By Step Answer:
In a reaction, rate is given by $ R = k\left[ A \right]\left[ B \right] $
Where Rate is the rate of a reaction and k is the rate constant of the reaction.
Rate constant k is the proportionality constant in the rate law expression. On increasing the concentration of any of the ions there is an increase in the rate of a reaction as the rate of a reaction is directly dependent on the concentration of the reactants, but this is not the case with the rate constant. The rate constant will not affect increasing the concentration of the reactant.
Same is the case in the above reaction. In our reaction also Rate = $ k{\text{ }}\left( {{H_2}{O_2}} \right)\left( {{H^ + }} \right)\left( {B{r^ - }} \right) $
Here also it is visible that if we increase the concentration of any of the ions, the rate of the reaction will increase accordingly but the rate constant will not have any effect and it will remain the same.
Therefore on increasing the bromide ion concentration, the rate constant will remain the same and there will not be any effect.

Note :
Rate constant being a constant does not change with the change in concentration of any of the reactants but it does affect when the temperature comes into the picture. Any temperature change will change the rate constant also along with the rate of the reaction. This can be understood well when you look into Arrhenius equation: $ k = A{e^ - }^{Ea/(RT)} $ where k is rate constant, A is frequency, -Ea is the activation energy, R is gas constant and T is temperature.