The reaction between `Cr_(2)O_(7)^(2-)` and `HNO_(2)` in an acidic medium is
`Cr_(2)O_(7)^(2-) + 5H^(o+) + 3HNO_(2) rarr 2Cr^(3+) + 3NO_(3)^(ɵ) + 4H_(2)O`.
The rate of disappearance of `Cr_(2)O_(7)^(2-)` is found to be `2.4 xx 10^(-4) mol L^(-1) s^(-1)` during measured time interval. What will be the rate of disappearance of `HNO_(2)` during the same time interval?

Options

A. `2.4xx10^(-4)`
B. `7.2xx10^(-4)`
C. `4.8xx10^(-4)`
D. `0.8xx10^(-4)`

Answer

B

Explanation

Rate `= (-d[Cr_(2)O_(7)^(2-)])/(dt) = (1)/(3) (-d[HNO_(2)])/(dt)`
or `(d[HNO_(2)])/(dt) = (3d[Cr_(2)O_(7)^(2-)])/(dt)`
`:. (d[HNO_(2)])/(dt) = 3 xx 2.4 xx 10^(-4) = 7.2 xx 10^(-4)`