Question

In an electrolysis experiment such as the one you are going to perform, 47.4 mL of hydrogen gas were collected. The temperature was 23 degrees Celsius and the barometric pressure was 643 mm Hg. The vapor pressure of water at 23 degrees Celsius is 21 mm Hg. The number of moles of hydrogen gas formed in the experiment was ___.

Answer 1

Answer: 0.0016 moles

Explanation:

According to the ideal gas equation:

$PV=nRT$

P = Pressure of the gas =  barometric pressure - vapor pressure of water =  (643-21) mm Hg = 622 mm Hg = 0.82 atm    (1 atm = 760 mmHg)

V= Volume of the gas = 47.4 ml = 0.0474 L     (1L=1000 ml)

T= Temperature of the gas = 23°C = 296 K (0°C = 273 K)

R= Gas constant = 0.0821 atmL/K mol

n= moles of gas = ?

$n=\frac{PV}{RT}=\frac{0.82\times 0.0474}{0.0821\times 296}=0.0016moles$

Thus the number of moles of hydrogen gas formed in the experiment was 0.0016.