Question

One mole of a gas exhibiting ideal behavior is enclosed in vessel of 1 litre capacity and is placed in a reservoir at temperature T(K). The pressure recorded in a flask is 2 bar. If the pressure in the flask is to be changed to 1.5 bar, how many molecules of the gas must escape out from the vessel?

• A. $25\%$
• B. $30\%$
• C. $12.5\%$
• D. $6\%$

Answer 1

The correct option is A $25\%$

Since V and T are constant, P $\propto$ n
For 2 bar pressure, the no. of moles = 1.0
For 1.5 bar pressure, the no. of moles $=\frac{1.5}{2}=0.75$
no.of moles escaped out = 1 – 0.75 = 0.25 mol (or) $25\%$