The solubility of Na3AsO4(H2O)12 is 38.9g per 100g H2O. What is the mass percentage of Na3AsO4 in the saturated solution?
(As = 75, Na = 23, O = 16, H = 1)
87.27%
38.9%
19.1%
13.7%
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The correct answer is option D.
Check for the correct answer here
https://youtu.be/AZEPFyE0QDI
Thank u bro. this was exactly what i lso did, i dont know why myschool wants to confuse s. This is the second time today.
We are given:
Solubility of Na₃AsO₄·12H₂O = 38.9 g per 100 g of water
But the question asks for mass % of Na₃AsO₄ (the anhydrous salt) in the saturated solution, not the hydrated salt.
1. Find molar masses
For Sodium arsenate (Na₃AsO₄)
So:
Molar mass of Na₃AsO₄ = 208
For Na₃AsO₄·12H₂O
2. Find fraction of Na₃AsO₄ in the hydrate
So the mass of Na₃AsO₄ in 38.9 g of Na₃AsO₄·12H₂O is
3. Total mass of saturated solution
4. Mass percentage of Na₃AsO₄
✅ Correct answer: D — 13.7%
