Question

How many liters of H2 at STP can be produced from the electrolysis of aqueous NaCl using a current of 50.0 mA for 1.0 hour?

Answer 1

The electrolysis of brine, aqueous sodium chloride solution, NaCl(aq) produces hydrogen gas, H2(g) at the -ve electrode and chlorine gas, Cl2(g) at the positive electrode
2H+(aq) + 2e- ==> H2(g) and 2Cl-(l/aq) - 2e- ==> Cl2(g)

AMount of charge passed = I*t
                     = (50*10^-3 A) * (3600 s)
                      = 180 Coulomb

Charge of 1 electron = 1.6*10^-19 C
Number of electron passed = 180 / (1.6*10^-19)
                                                         = 1.125*10^21 electron

1 molecule of H2 is formed by 2 electron.
So, number of molecules of H2 formed = 1.125*10^21 /2 = 5.625*10^20
Number of moles of H2 = 5.625*10^20 / (6.022*10^23) = 9.341*10^-4 Moles

use:
PV=n*R*T
1*V = (9.341*10^-4 ) * 0.0821 * 273
V = 0.021 L

Answer: 0.021 L