Answer to Question #148312 in Chemistry for Kristia Panares

Question

What mass of H2O is required to react with 1.5 g of Na2S2O3 ?
Step 2: Mass to moles
Step 3: Mole to Mole (Ratio)
Step 4: Mole to Mass

Answer 1

The balanced reaction equation of cloth bleach using Na2S2O3 and chlorine is:

Na₂S₂O₃(aq) + 4Cl₂(g) + 5H₂O(aq) $\rightarrow$ 2NaHSO₄(aq) + 8HCl(aq)

The number of the moles of Na₂S₂O₃ is its mass (1.5 g) divided by its molar mass:

158.11 g/mol:

$n = \frac{m}{M} = \frac{1.5}{158.11} = 0.0095$ mol.

According to the reaction equation, one molecule of Na₂S₂O₃ reacts with five molecules of H₂O:

$n(Na_2S_2O_3) = \frac{n(H_2O)}{5}$

$n(H_2O) = 5·n(Na_2S_2O_3) = 5·0.0095 = 0.047$ mol.

Therefore, the mass of water needed is:

$m(H_2O)= nM = 0.047·18.02 = 0.855$ g.

Answer: 0.855 g of H₂O is required to react with 1.5 g of Na₂S₂O₃.