The rate constant of a first order reaction is `0.0051"min"^(-1)` . If the initial concentration of the reactant is 0.2(M) , find the concentration of the reactant after 2h.

Explanation

The rate constant of first order reaction, `k=(2.303)/(t)log.([A]_(0))/([A]), " where"[A]_(0) and [A]` are the concentrations of the reactant at t = 0 and at time t respectively.
Given, `k=0.0051"min"^(-1),t=2h=2xx60=120"min",`
`[A]_(0)=0.2(M),[A]=?`
`therefore0.0051=(2.303)/(120)log.(0.2)/([A])" or, "log.(0.2)/([A])=0.2657`
`therefore[A]=0.1085(M)`
Hence , concentration of the reactant after 2h is 0.1085(M).