Question

The compound sodium thiosulfate pentahydrate, Na₂S₂O₃·5H₂O, is important commercially to the photography business as "hypo", because it has the ability to dissolve unreacted silver salts from photographic film during development. Sodium thiosulfate pentahydrate can be produced by boiling elemental sulfur in an aqueous solution of sodium sulfite.

S₈(s) + Na₂SO₃(aq) + H₂O(l) →

Na₂S₂O₃·5H₂O(s) (unbalanced)

What is the theoretical yield of sodium thiosulfate pentahydrate when 2.95 g of sulfur is boiled with 13.6 g of sodium sulfite?

Sodium thiosulfate pentahydrate is very soluble in water. What is the percent yield of the synthesis if a student doing this experiment is able to isolate (collect) only 5.01 g of the product?

Answer 1

What is the theoretical yield of sodium thiosulfate pentahydrate when 2.95 g of sulfur is boiled with 13.6 g of sodium sulfite?

balanced the equation:

S8 + 8 Na2SO3 + 40 H2O = 8 Na2S2O3*5H2O

2.95 g S8 / (256.52 g/mol) = . 0.0115 mol S8

13.6 g Na2SO3 / (126.0433 g/mol) = .10789 mol Na2SO3

mole ratio between Na2SO3 and S8 should be 8, but it is slightly more (8.2 ish), so S8 is the LR.

0.0115 mol S8 * (8 mol Na2S2O3*5H2O / 1 mol S8) = 0.092 mol Na2S2O3*5H2O

0.092mol Na2S2O3*5H2O * (248.1854 g/mol) = 22.833g Na2S2O3*5H2O = Theoretical yield -answer

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Sodium thiosulfate pentahydrate is very soluble in water. What is the percent yield of the synthesis if a student doing this experiment is able to isolate (collect) only 5.01 g of the product?

b)

5.01 g / 22.833g = 0.219% yield-answer