Question

26.8 g Na2SO4.nH2O has 12.6 g water.find the value of n

Answer 1

Na2SO4 * n H2O

Molar mass of salt = (142 + 18n)

Mass of water = 12.6 / 26.8 x (142 + 18n)

18 n = 12.6/26.8 (142 + 18n)

n = 7

Answer 2

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Molar mass  of Na₂SO₄  = 142 g 

Molar mass of water = 18 g 

Molar mass of given salt = 142 + 18 n 

Mass of water = $\frac{12.6}{26.8} (142+18n)$

482 . 4 n          = 12.6(142 + 18n) 

 482.4 n            = 1789.2 + 226.8 n 

255.6 n             = 1789 . 2 

n                       = 1789.2/ 255.6 = 7 
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