Answer:
The pressure in the new flask would be [tex]128\; \rm mmHg[/tex] if the [tex]\rm HCl[/tex] here acts like an ideal gas.
Explanation:
Assume that the [tex]\rm HCl[/tex] sample here acts like an ideal gas. By Boyle's Law, the pressure [tex]P[/tex] of the gas should be inversely proportional to its volume [tex]V[/tex].
For example, let the initial volume and pressure of the sample be [tex]V_1[/tex] and [tex]P_1[/tex]. The new volume [tex]V_2[/tex] and pressure [tex]P_2[/tex] of this sample shall satisfy the equation: [tex]P_1 \cdot V_1 =P_2 \cdot V_2[/tex].
In this question,
The goal is to find the new pressure of this gas, [tex]P_2[/tex].
Assume that this sample is indeed an ideal gas. Then the equation [tex]P_1 \cdot V_1 =P_2 \cdot V_2[/tex] should still hold. Rearrange the equation to separate the unknown, [tex]P_2[/tex]. Note: make sure that the units for [tex]V_1[/tex] and [tex]V_2[/tex] are the same before evaluating. That way, the unit of
[tex]\begin{aligned} & P_2\\ &= \frac{P_1 \cdot V_1}{V_2} \\ &= \frac{256\; \rm mL \times 67.5\; \rm mmHg}{135\; \rm mL} \\ & \approx 128\; \rm mmHg\end{aligned}[/tex].
