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If the given reaction \mathrm{A(g) \rightarrow B(g)+2(g)} take place at constant pressure and 300 k, what will be the concentration of A after 300 sec. It is a first order reaction, where the starting amount of A was 0.1 mole in a 3 L container and rate constant is \mathrm{\quad 2.552 \times 10^{-3} \mathrm{~s}^{-1}}

Option: 1

0.0125 M


Option: 2

0.025 M


Option: 3

0.083 M


Option: 4

None


Answers (1)

best_answer

\mathrm{\begin{aligned} t_{1 / 2} & =\frac{0.693}{k} \\ & =\frac{0.693}{2.552 \times 10^{-3}} \\ & =271.5 \mathrm{~s} \end{aligned}}

Since volume is changing $\therefore$ half life should be defined on the basis of moles, so moles of A remaining after 300 s : Also, final volume of the container

\mathrm{\begin{aligned} v_f & =\frac{n_f}{n_i} \times v_i \\ & =\frac{0.05+0.15}{0.1} \times 3 \\ & =6 \mathrm{~L} \end{aligned}}

Final concentration of \mathrm{\begin{aligned} A & =\frac{0.05}{6} & =0.0083 \mathrm{M} \end{aligned}}

Posted by

Sanket Gandhi

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