Step 1: Use the adiabatic condition.
For an adiabatic process, the relation between pressure and temperature is given by:
\[
P_1 T_1^{\gamma} = P_2 T_2^{\gamma}
\]
where \( \gamma \) is the adiabatic index, \( T_1 \) and \( T_2 \) are the initial and final temperatures, and \( P_1 \) and \( P_2 \) are the initial and final pressures.
Step 2: Apply the given condition.
It is given that the final temperature \( T_2 \) is twice the initial temperature \( T_1 \):
\[
T_2 = 2 T_1
\]
Substitute into the adiabatic equation:
\[
P_1 T_1^{\gamma} = P_2 (2 T_1)^{\gamma}
\]
\[
P_1 = P_2 \cdot 2^{\gamma}
\]
Thus, the ratio of final pressure to initial pressure is:
\[
\frac{P_2}{P_1} = 2^{\gamma}
\]
For a mono-atomic ideal gas, \( \gamma = \frac{5}{3} \), so:
\[
\frac{P_2}{P_1} = 2^{\frac{5}{3}} \approx 16
\]