$2 \times {10^{ - 5}} = K \times {10^{ - 2}}$
$K = 2 \times {10^{ - 3}}\,{\sec ^{ - 1}}$
${t_{1/2}} = \frac{{.693}}{K} = \frac{{.693}}{{2 \times {{10}^{ - 3}}}} = \frac{{693}}{2} = 347\,\sec $
| No | $[NH_4^+]$ | $[NO_2^-]$ | rate of reaction |
| $1.$ | $0.24\, M$ | $0.10\, M$ | $7.2 \times {10^{ - 6}}$ |
| $2.$ | $0.12\, M$ | $0.10\, M$ | $3.6 \times {10^{ - 6}}$ |
| $3.$ | $0.12\, M$ | $0.15\, M$ | $5.4 \times {10^{ - 6}}$ |