Test Index

VITEEE 2017 Paper

Section: Chemistry

© examsnet.com

Question : 65 of 125

Marks: +1, -0

The half life of the first order reaction

\mathrm{CH}_3 . \mathrm{CHO}

\mathrm{CH}_4

If initial pressure of

\mathrm{CH}_3\mathrm{CHO}

(g) is 80 mm Hg and the total pressure at the end of 20 minutes is 120 mm Hg

80 min
120 min
20 min
40 min

Solution:

\underset{\text{When } t = 0 ; p^0 - p}{\underset{\text{When } t = 0 \; p^0}{\mathrm{CH}_3\mathrm{CHO}}}

(g) →

\underset{p}{\underset{0}{\mathrm{CH}_4}}

(g) +

\underset{p}{\underset{0}{\mathrm{CO}}}

(g)

∴

p^0

- p + p + p = 120 mm Hg

or ,

p^0

+ p = 120 mm Hg

p = 120 - 80 = 40 mm Hg

k =

\frac{1}{t}

ln

\frac{p^0}{p^0-p}

= 1/{20}$

\ln

{80}/{80-40}

=

1/{20}

\ln 2 \\ \text{Again ,}

t_{1\/2}

=

{ln2}/k

\\ \therefore

t_{1\/2}$ ${ln2}/{ln2}$ × 20 = 20 min

© examsnet.com

Go to Question:

Prev Question

Next Question