Question

A mixture of $100\text{mL}$ of $CO,C{O}_2$ and $O_2$ was sparked. When the resulting gaseous mixture was passed through $KOH$ solution, the contraction in volume was found to be $80\text{mL}$. The composition of the initial mixture may be (in the same order):

• A. 20 mL, 50 mL, 30 mL
• B. 40 mL, 20 mL, 40 mL
• C. 30 mL, 50 mL, 20 mL
• D. 30 mL, 40 mL, 30 mL

Answer 1

Answer: (A), (B)

40 mL, 20 mL, 40 mL

Let the initial volume of $CO,C{O}_2$ and $O_2$ be a, b and c respectively.

Then, $a+b+c=100$.........(i)

After the reaction, $CO+\frac{1}{2}{O}_2\to C{O}_2$ and the treatment with KOH, a contraction of 80 mL was observed.
This is due to the consumption of oxygen and the absorbtion of $C{O}_2$
$a+b+\frac{a}{2}=80$ ..............(ii)

Also,
$c-\frac{a}{2}=20$............ (iii)

The options should satisfy all the three equations.

a) a = 20 mL b = 50 mL c = 30 mL
It satisfies all the three equations.

b) a = 40 mL b = 20 mL c = 40 mL
It satisfies all the three equations.