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### The decomposition of formic acid on gold surface follows ....

The decomposition of formic acid on gold surface follows first order kinetics. If the rate constant at 300 K is $1.0 \times 10^{-3} s^{-1}$ and the activation energy $E_a = 11.488 kJ.mol^{-1}$, the rate constant at 200 K is _ _ _ _ $\times 10^{-5} s^{-1}$. (Round off to the nearest integer)

[Given $R = 8.314 J mol^{-1} K^{-1}$]

Solution

We have, $\log \frac{{{K_2}}}{{{K_1}}} = \frac{{{E_a}}}{{2.303R}}\left( {\frac{{{T_2} - {T_1}}}{{{T_1}{T_2}}}} \right)$

$\Rightarrow \log \frac{{{K_2}}}{{1.0 \times {{10}^{ - 3}}}} = \frac{{11.488 \times 1000}}{{2.303 \times 8.314}}\left( {\frac{{200 - 300}}{{200 \times 300}}} \right)$

$\Rightarrow \log \frac{{{K_2}}}{{1.0 \times {{10}^{ - 3}}}} = - \frac{{11.488 \times 5}}{{2.303 \times 8.314 \times 3}} = - 1$

$\Rightarrow {K_2} = {10^{ - 4}} = 10 \times {10^{ - 5}}{s^{ - 1}}$

### Sum of the coefficients in the expansion of $(x+y)^n$ ....
If the sum of the coefficients in the expansion of $(x+y)^n$ is 4096, then the greatest coefficient in the expansion is _ _ _ _ . Solution $C_0 + C_1 + C_2 + C_3 + ......................... + C_n =4096$ $\therefore 2^n = 4096 =2^{12}$ $\Rightarrow n = 12$ Greatest coefficient = ${}^{12}{C_6} = 924$