Question

What is K in chemistry ?

Answer 1

Rate constant K

1. K is the rate constant that determines the relation between the molar concentration of reactant and the rate of reaction.
2. It depends on the temperature.
3. For a reaction that is at equilibrium we use K.
4. Equilibrium is when the concentration of reactant and product becomes equal.
5. This equilibrium constant helps us in determining whether the concentration of products or reactants is greater.
6. From this constant, we can determine whether a reaction will tend in the forwarding direction or backward direction.

Units of K

The units of K depends upon the order of reaction

Zero-order reaction	$\mathrm{mol}.{\mathrm{L}}^{-1}.{\mathrm{s}}^{-1}$
First-order reaction	${\mathrm{s}}^{-1}$
Second-order reaction	${\mathrm{M}}^{-1}.{\mathrm{s}}^{-1}$
Third-order reaction	${\mathrm{M}}^{-2}.{\mathrm{s}}^{-1}$

The effect of temperature on K.

1. This can be explained by the Arrhenius equation.
2. Arrhenius equation is given by -
   $$\begin{gathered} \mathrm{K}={\mathrm{Ae}}^{-\frac{\mathrm{Ea}}{\mathrm{RT}}} \\ \mathrm{where},\mathrm{K}\mathrm{is}\mathrm{the}\mathrm{rate}\mathrm{constant} \\ \mathrm{A}\mathrm{is}\mathrm{the}\mathrm{pre}\mathrm{exponential}\mathrm{factor} \\ \mathrm{Ea}\mathrm{is}\mathrm{the}\mathrm{activation}\mathrm{energy} \\ \mathrm{R}\mathrm{is}\mathrm{the}\mathrm{gas}\mathrm{constant} \\ \mathrm{T}\mathrm{is}\mathrm{the}\mathrm{temperature} \end{gathered}$$
3. Rate constant is increased as temperature increases.
4. There is an exponential increase of rate constant with the temperature.