Question

The following data is obtained during the first order thermal decomposition of $2A_{(g)} \rightarrow B_{(g)} + C_{(s)}$, at constant volume and temperature The rate constant in $min^{-1}$ is

• A. $0.0693$
• B. $69.3$
• C. $6.93$
• D. $0.00693$

Answer 1

Answer: (A)

$0.0693$

Answer 2

$\underset{2-2x}{2A(g)} \to B \underset{x}{(g)}+C(s)$ At the end of reaction, only 1 mole of gas is present whose pressure is 200 pascal. $\therefore$ At the beginning of the reaction 2 moles of gas should have a pressure of 400 pascal. After time 10 min No. of moles present, $2-2 x+x=2-x$ The pressure of 2 moles $=400$ $400-x=300$ $\therefore\,x=100$ $\therefore$ Pressure due to $2-2 x$ moles of $A$ $=400-200=200$ $\therefore k =\frac{2.303}{t} \log \left(\frac{a}{a-x}\right)=\frac{2.303}{10} \log \left(\frac{400}{200}\right)$ $=\frac{2.303}{10} \log 2=\frac{0.693}{10}$ $=0.0693\, min ^{-1}$