Question

Sodium sulfide, Na₂S, is used in the leather industry to remove hair from hides. The Na₂S is made by the reaction

Na₂SO₄(s) + 4 C(s) → Na₂S(s) + 4 CO(g).

Suppose you mix 19.0 g of Na₂SO₄ and 6.30 g of C. What mass of Na₂S is produced?

_____ g Na₂S

Answer 1

Molar mass of Na2SO4 = 2*MM(Na) + 1*MM(S) + 4*MM(O)

= 2*22.99 + 1*32.07 + 4*16.0

= 142.05 g/mol

mass of Na2SO4 = 19.0 g

we have below equation to be used:

number of mol of Na2SO4,

n = mass of Na2SO4/molar mass of Na2SO4

=(19.0 g)/(142.05 g/mol)

= 0.1338 mol

Molar mass of C = 12.01 g/mol

mass of C = 6.3 g

we have below equation to be used:

number of mol of C,

n = mass of C/molar mass of C

=(6.3 g)/(12.01 g/mol)

= 0.5246 mol

we have the Balanced chemical equation as:

Na2SO4 + 4 C ---> Na2S + 4 CO

1 mol of Na2SO4 reacts with 4 mol of C

for 0.1338 mol of Na2SO4, 0.535 mol of C is required

But we have 0.5246 mol of C

so, C is limiting reagent

we will use C in further calculation

Molar mass of Na2S = 2*MM(Na) + 1*MM(S)

= 2*22.99 + 1*32.07

= 78.05 g/mol

From balanced chemical reaction, we see that

when 4 mol of C reacts, 1 mol of Na2S is formed

mol of Na2S formed = (1/4)* moles of C

= (1/4)*0.5246

= 0.1311 mol

we have below equation to be used:

mass of Na2S = number of mol * molar mass

= 0.1311*78.05

= 10.2 g

Answer: 10.2 g