Question

Chlorine is produced industailly by the electrolysis of brine. The reaction is described by the equation

2NaCl (aq) + 2H20 (l) ---------------> 2NaOH (aq) + Cl2 (g) + H2

(electrolysis)

How many kilograms of each product can be obtained from the electrolysis of salt that is 95% sodium chloride by mass?

Answer 1

We have reaction given as :

2NaCl (aq) + 2H₂O (l) ---------------> 2NaOH (aq) + Cl₂ (g) + H₂(g)

In reactant

Mass of 2 mol NaCl = 58.44 x 2 = 116.88g

Mass of 2 mol H₂O = 36g

In product

Mass of 2 mol NaOH = 80g

mass of 1 mol Cl₂ = 70.9g

mass of 1 mol H₂ = 2g

for 116.88g NaCl , 80g NaOH , 70.9g Cl₂ and 2g H₂ is produced

for 1 g NaCl 80g/116.88 NaOH , 70.9g/116.88 Cl₂ and 2g/116.88 H₂ is produced

1kg = 1000g

and it has 95% NaCl = 950g

NaOH = 80g/116.88 x 950 = 650.24g = 0.65 kg/ kg salt

Cl₂ = 70.9g/116.88 x 950 = 576.27g = 0.576 kg/kg salt

H₂ = 2g/116.88 x 950 = 16.26 g = 0.016 kg/kg salt

when water is in abundant

**In case it is 95% mass in solution and not 95% NaCl in salt then,H₂O will become limiting reactant

from reaction equation we see that for 116.88 g NaCl requires 36g H₂O

for 950 g NaCl requires 36/116.88 x 950 g H₂O = 292.6 g H₂O

but we have only 50g and hence it is limiting reactant and product formed will be based on this only

36g or 2 mol H₂O gives   80g NaOH , 70.9g Cl₂ and 2g H₂

1 g H₂O will give 80g / 36 H₂O , 70.9 g/36 Cl₂ and 2g/36g H₂

50g will give 80g/36 x 50 70.9g/36 x 50 2g/36 x 50

= 111.11g H₂O   98.47g Cl₂   2.78 g H₂

in kilograms = 0.11 kg 0.098kg 0.002kg

** i didn't get the question initially and hence i solved this so that why i kept it.

you may not require this.

thanks!