A0.325 l flask filled with gas at 0.914 atm and 19 °c contains mol of gas.

To calculate for the number of moles of the gas, we need a relation to relate the number of moles (n), pressure (P), and temperature (T) with volume (V). There are a number of equations that available for use. However, some of these equation are complex which needs other parameters. For simplicity, we assume the gas is an ideal gas. So, we use PV=nRT.

PV = nRT  where R is the universal gas constant
n = PV / RT

n = (0.914 atm) (0.325 L) / (0.08205 L-atm / mol-K) (19 + 273.15 K)

n = 0.0124 mol

Therefore, for the given conditions, we will have 0.0124 mol of gas.

3 hours because it is a decent distance.