Since the temperature of the gas remains constant in the process, we can use Boyle's law, which states that for a gas transformation at constant temperature, the product between the gas pressure and its volume is constant:
[tex]pV=k[/tex]
which can also be rewritten as
[tex]p_1 V_1 = p_2 V_2[/tex] (1)
where the labels 1 and 2 mark the initial and final conditions of the gas.
In our problem, [tex]p_1 = 1.5 atm[/tex], [tex]V_1 =6.5 L[/tex] and [tex]V_2 =13.0 L[/tex], so the final pressure of the gas can be found by re-arranging eq.(1):
[tex]p_2 = p_1 \frac{V_1}{V_2}= (1.5 atm) \frac{6.5 L}{13.0 L}=0.75 atm [/tex]
Therefore the correct answer is
1. 0.75 atm