Question

Chlorine is used by textile manufacturers to bleach cloth. Excess chlorine is destroyed by its reaction with sodium thiosulfate, Na2S2O3, as follows:Na2S2O3(aq) + 4Cl2( g) + 5H2O 2NaHSO4(aq) + 8HCl(aq)(a) How many moles of Na2S2O3 are needed to react with 0.36 mol of Cl2?(b) How many moles of HCl can form from 0.19 mol of Cl2?(c) How many moles of H2O are required for the reaction of 0.46 mol of Cl2?(d) How many moles of H2O react if 0.39 mol HCl is formed?

Answer 1

1) Chemical equation

`Na_2S_2O_(3(aq))+4Cl_(2(g))+5H_2O\rightarrow2NaHSO_(4(aq))+8HCl_((aq))`

2) Moles of Na2S2O3 needed to react with Cl2 (a).

The molar ratio

1 mol Na2S2O3: 4 mol Cl2

`molNa_2S_2O_3=0.36molCl_2\cdot(1molNa_2S_2O_3)/(4molCl_2)=0.09molNa_2S_2O_3`

(a) We need 0.09 mol Na2S2O3 to react with 0.36 mol Cl2.

3) Moles of HCl formed from Cl2 (b).

The molar ratio

8 mol HCl: 4 mol Cl2

`molHCl=_{}0.19molCl_2\cdot\frac{8molHCl_{}}{4molCl_2}=0.38molHCl`

(b) 0.19 mol Cl2 can form 0.38 mol HCl

4) Moles of H2O required for the reaction of Cl2 (c).

The molar ratio

5 mol H2O: 4 mol Cl2

`molH_2O=0.46molCl_2\cdot(5molH_2O)/(4molCl_2)=0.575molH_2O`

(c) 0.575 mol H2O are required for the reaction of 0.46 mol Cl2.

5) Moles of H2O to form HCl

The molar ratio

5 mol H2O: 8 mol HCl

`mol_{}H_2O=0.39molHCl\cdot\frac{5molH_2O}{8molHCl_{}}=0.24375molH_2O_{}`

(d) 0.24375 mol H2O is needed to form 0.39 mol HCl.