An open ended mercury manometer is used to measure the pressure exerted by a trapped gas as shown in the figure. Initially manometer shows no difference in mercury level in both columns as shown in diagram.

After sparking A dissociates according to following reaction:
$2 A (g) ⟶ 3 B (g) + 2 C (g)$
If pressure of Gas A decreases to 0.8 atm. Then :
(Assume temperature to be constant at 300 K)

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total pressure increased by 22.3 cm of Hg

(a) total pressure increased byl.3 atm

total pressure increased by 0 .3 atm

difference in mercury level is 228 mm

answer is B, D.

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Detailed Solution

$\begin{array}{l} 2 A ⟶ 3 B + 2 C \\ \begin{array}{lll} 1 s t x & \bar{3 x} & - \\ 1 - x & \frac{3 x}{2} & x \\ = 0.8 \\ \Rightarrow x = 0.2 & 0.3 & 0.2 \end{array} \end{array}$

Total pressure now $= 0.8 + 0.3 + 0.2 = 1.3$ atm

Difference in column $= 0.3 \times 760 = 228$ mm.

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