Answer
For part A: The final pressure of the helium gas = 292.2 mmHg
For part B: The final pressure of the helium gas = 1920 mmHg.
Explanation
Part A:
The final pressure, in mmHg of the helium gas, can be calculated using Boyle's law formula:
[tex]P_1V_1=P_2V_2[/tex]Putting
[tex]\begin{gathered} V_1=10.5\text{ }L \\ \\ P_1=640\text{ }mmHg \\ \\ V_2=23.0\text{ }L \\ \\ P_2=? \end{gathered}[/tex]We have:
[tex]\begin{gathered} 640mmHg\times10.5L=P_2\times23.0L \\ \\ Divide\text{ }both\text{ }sides\text{ }by\text{ }23.0L \\ \\ P_2=\frac{640mmHg\times10.5L}{23.0L} \\ \\ P_2=292.2\text{ }mmHg \end{gathered}[/tex]For part A: The final pressure of the helium gas is 292.2 mmHg.
Part B:
Similarly, the final pressure, in mmHg of the helium gas, can be calculated using Boyle's law formula:
[tex]P_1V_1=P_2V_2[/tex]Putting
[tex]\begin{gathered} V_1=10.5\text{ }L \\ \\ P_1=640\text{ }mmHg \\ \\ V_2=3.50\text{ }L \\ \\ P_2=? \end{gathered}[/tex]We have:
[tex]\begin{gathered} 640mmHg\times10.5L=P_2\times3.50L \\ \\ Divide\text{ }both\text{ }sides\text{ }by\text{ }3.50L \\ \\ P_2=\frac{640mmHg\times10.5L}{3.50L} \\ \\ P_2=1920\text{ }mmHg \end{gathered}[/tex]For part B: The final pressure of the helium gas is 1920 mmHg.