Question

In the diagram, bulbs are filled with same gas. The pressure in 1 L bulb is 1.5 atm and pressure in 4 L bulb is 2 atm. If the temperature remains constant and valve between the two bulbs is opened, then what is final pressure. If the volume of connecting tube is negligible?

• A. 1.75 atm
• B. 1.8 atm
• C. 1.85 atm
• D. 1.9 atm

Answer 1

The correct option is D 1.9 atm

Total moles remains conserved
$(n_A+n_B{)}_{\text{before}}=(n_A^{\prime }+n_B^{\prime })$ after
volume of the ${\text{bulb}}_1=1\text{L}$
pressure of the ${\text{bulb}}_1=1.5\text{atm}$
number of moles in ${\text{bulb}}_1=\frac{1.5\times 1}{R\times T}$
volume of the ${\text{bulb}}_2=4\text{L}$
pressure of the ${\text{bulb}}_2=2\text{atm}$
number of moles in ${\text{bulb}}_2=\frac{2\times 4}{R\times T}$
Hence total moles =
$\frac{1.5\times 1}{R\times T}+\frac{2\times 4}{RT}=\frac{P_f\left(5\right)}{RT}$

$\Rightarrow 1.5+8=5P_f$
$\Rightarrow P_f=1.9\text{atm}$