Get Answers to all your Questions

header-bg qa

Calculate the amount of acetic acid in one litre of its solution. Given, degree of dissociation is 2% and \mathrm{Ka = 1.8\times10^{-5}}

Option: 1

2.7 g

Option: 2

27 g

Option: 3

10.8 g

Option: 4

5.4 g

Answers (1)


According to question,

\mathrm{CH}_{3} \mathrm{COOH} \rightleftharpoons \mathrm{CH}_{3} \mathrm{COO}^{-}+\mathrm{H}^{+}

          1                            0                      0

        1-\alpha                          \alpha                    \alpha

here \alpha is degree of dissociation.


 \mathrm{K_{a}=\frac{\left[\mathrm{CH}_{3} \mathrm{COO}^{-}\right]\left[\mathrm{H}^{+}\right]}{\left[\mathrm{CH}_{3} \mathrm{COOH}\right]}=\frac{c \alpha \cdot c \alpha}{c(1-\alpha)}=\frac{c \alpha^{2}}{(1-\alpha)}}

As dissociation constant is very less than 1, so 1-\alpha \approx 1

\mathrm{\therefore K_{a} = c\alpha ^{2}}

\mathrm{\Rightarrow 1.8\times 10^{-5}=c\times \left ( \frac{2}{100} \right )^{2}}

\mathrm{c = 0.045\: mole/litre}

\text{Amount of acetic acid in 1 litre} \mathrm{= 60 \times 0.045 = 2.7\ g}

Hence, the correct answer is Option (1)


Posted by


View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE