Question

calculate the mass of Mg and volume of chlorine gas STP produced during electrolysis of molten MgCl2 by the passage of 2 amperes of current for 1 hour .Molar masses of Mg and Cl2 are respectively 24 g mol-1 and 71 g mol-1.​

Answer 1

current passing through electrolyte , I = 2A

and time taken , t = 1 hour.

so, charge flows through electrolyte during 1 hour , Q = 2A × 3600sec = 7200 C

we know, 1 mole of electrons is equivalent 96500 C charges.

so, number of mole of electron = 7200/96500 = 0.075 mol.

reaction at cathode, $Mg^{2+}+2e^-\rightarrow Mg$

it means, 2 moles electron require to form 1 mole of Mg.

so, 0.075mol of electron forms , 0.075/2 mol of Mg.

so, mass of Mg = 0.075/2 × atomic mass

= 0.075/2 × 24

= 0.075 × 12

= 0.9g

hence, mass of Mg is 0.9g.

now, equivalents of Mg = equivalents of Cl2

or, 0.9/{24/2} = mass of Cl2/{71/2}

or, 0.9/24 × 71 = mass of Cl2

it means, mole of Cl2 = 0.9/24 mol

and then, volume of Cl2 = 22.4 × 0.9/24 L

= 0.84L = 840ml

Answer 2

Answer:

current passing through electrolyte , I = 2A

and time taken , t = 1 hour.

so, charge flows through electrolyte during 1 hour , Q = 2A × 3600sec = 7200 C

we know, 1 mole of electrons is equivalent 96500 C charges.

so, number of mole of electron = 7200/96500 = 0.075 mol.

reaction at cathode, Mg^{2+}+2e^-\rightarrow MgMg

2+

+2e

−

→Mg

it means, 2 moles electron require to form 1 mole of Mg.

so, 0.075mol of electron forms , 0.075/2 mol of Mg.

so, mass of Mg = 0.075/2 × atomic mass

= 0.075/2 × 24

= 0.075 × 12

= 0.9g

hence, mass of Mg is 0.9g.

now, equivalents of Mg = equivalents of Cl2

or, 0.9/{24/2} = mass of Cl2/{71/2}

or, 0.9/24 × 71 = mass of Cl2

it means, mole of Cl2 = 0.9/24 mol

and then, volume of Cl2 = 22.4 × 0.9/24 L

= 0.84L = 840ml