Question

The initial concentratin of `N_(2)O_(5)` in the following first order reaction
`N_(2)O_(5)(g) to 2NO_(2)(g)+(1)/(2O_(2))(g) was 1.24 xx10^(-2) mol L^(-1)` at 318K. The concentration of `N_(2)O_(5)` after 60 minutes was `0.20xx10^(-2) mol L^(-1).` Calculate the rate constant of the reaction at 138 K.

Answer 1

For a first order reaction
`log ""([R]_(1))/([R]_(2))=(k(t_(2)-t_(1)))/(2.303)`
`k= (2.303)/((t_(2)- t_(1)))log ""([R_(1)])/([R]_(2))`
`=(2.303)/((60 min -0min ))log ""(1.24xx10^(-2)mol L ^(-1))/(0.20xx10^(-2)mol L^(-1))`
`=(2.303)/(60)log 6.2 min ^(-1)`
`k=0.0304min^(-1).`