Question

A sample of hydrated sodium thiosulfate has a mass of 6.584 g. After it is heated, it has a mass of 4.194 g. What is the percentage by mass of water in the hydrate?

Answer 1

36.30%

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Answer 2

Na₂S₂O₃·xH₂O → Na₂S₂O₃ + xH₂O

w(H₂O)=100m(H₂O)/m₀

m(H₂O)=m₀-m₁

w(H₂O)=100(m₀-m₁)/m₀

w(H₂O)=100(6.584-4.194)/6.584=36.30%