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Question: Write four differences between rate of reaction and rate constant....

Write four differences between rate of reaction and rate constant.

Explanation

Solution

For this we need to have understanding of chemical kinetics. Both of them have their own physical significance and meaning.

Complete step by step solution:
Let us look at both of them one by one:
1.Rate of reaction: It is defined as the change in concentration of reactant or product per unit time. The expression for rate in terms of change in concentration pr reactant and product is:
2. Rate = change in concentration of reactant or producttime{\text{Rate = }}\dfrac{{{\text{change in concentration of reactant or product}}}}{{{\text{time}}}}
3.Rate can either be defined in terms of reactant R or product P as Rate = - d[R]dt=d[P]dt{\text{Rate = - }}\dfrac{{{\text{d}}\left[ {\text{R}} \right]}}{{{\text{dt}}}} = \dfrac{{{\text{d}}\left[ {\text{P}} \right]}}{{{\text{dt}}}}
4.Since as reaction proceeds concentration of reactant keeps on decreasing, so change in concentration of reactant will be negative. That is why negative sign is there while defining the rate in terms of reactants to make the overall value positive. Because the rate of the reactant can never be negative.
5.The unit of rate is mol L−1 s−1{\text{mol }}{{\text{L}}^{ - 1}}{\text{ }}{{\text{s}}^{ - 1}}
Now coming to rate constant:
1.It is a constant of proportionality, in the reaction giving the relationship between rate of the reaction and concentration of reactant.
2.the rate constant K can be defined using rate law as:
Rate ∝ [A]α{\text{Rate }} \propto {\text{ }}{\left[ {\text{A}} \right]^\alpha } Where α is order w.r.t reactant A\alpha {\text{ is order w}}{\text{.r}}{\text{.t reactant A}}
Rate = K [A]α{\text{Rate = K }}{\left[ {\text{A}} \right]^\alpha }
3.The unit of rate constant varies according to the order of reaction. The general formula of unit is given as , where n is the order of reaction
(mol L−1)1−n×s−1{({\text{mol }}{{\text{L}}^{ - 1}})^{1 - n}} \times {{\text{s}}^{ - 1}}
4.Rate constant is a function of temperature, if temperature changes the rate of reaction also changes.

Note:
Although rate of reaction and rate have different units, but for particularly zero order reaction they both have the same unit. If we put n = 1{\text{n = 1}}in the unit formula of rate constant we will get unit of rate constant as mol L−1 s−1{\text{mol }}{{\text{L}}^{ - 1}}{\text{ }}{{\text{s}}^{ - 1}} which is same as unit of rate of reaction.