Can you please answer part A? The vapor pressure of water changes with temperatu
ID: 513108 • Letter: C
Question
Can you please answer part A?
The vapor pressure of water changes with temperature, as shown here. A student designs an ammeter (a device that measures electrical current) that is based on the electrolysis of water into hydrogen and oxygen gases. When electrical current of unknown magnitude is run through the device for 4.00 min 6.9 mL of water-saturated H_2(g) is collected. The temperature and pressure of the system are 25 degree C and 715 torr. How many moles of hydrogen gas are produced? Express your answer to three significant figures and include the appropriate units.Explanation / Answer
Volume of H2, V = 16.9 mL = 0.0169 L
Temperature, T = 25 + 273.15 = 298.15 K
Pressure of H2,P=total preesure - vapour pressure of water=715-23.8=691.2torr=691.2 /760=0.909 atm
R = 0.0821 L.atm.K-1.mol-1
number of moles of H2, n = ?
Assuming ideal gas behaviour,
ideal gas equation, P V = n R T
n = P V / R T
n = 0.909 * 0.0169 / (0.0821 * 298.15)
n = number of moles of H2 produced = 6.28 * 10-4 mol