Zinc metal is added to hydrochloric acid to generate hydrogen gas,which is collected over a liquid whose vapor pressure is the same as pure water at 20.0°C (18 torr).The volume of the gas mixture is 1.7 L and its total pressure is 0.810 atm.
-Determine the number of moles of hydrogen gas present in the sample.
A)42 mol
B)0.82 mol
C)1.3 mol
D)0.056 mol
E)22 mol

Question

Quizplus · Accepted Answer

To find the moles of hydrogen gas, we use the ideal gas law equation, PV = nRT, where P is the pressure of hydrogen gas, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. First, convert the total pressure from atm to torr (0.810 atm * 760 torr/atm = 615.6 torr). The pressure of hydrogen gas is the total pressure minus the vapor pressure of water (615.6 torr - 18 torr = 597.6 torr or 0.787 atm). Convert the temperature to Kelvin (20°C + 273.15 = 293.15 K). Using R = 0.0821 L·atm/(mol·K), n = PV/(RT) = (0.787 atm * 1.7 L) / (0.0821 L·atm/(mol·K) * 293.15 K) = 0.056 mol.

Zinc Metal Is Added to Hydrochloric Acid to Generate Hydrogen