1.

The crystalline salt Na_2 SO_4.xH_2Oon heating loses 55.9 % of its weight. The formula of crystalline salt is

Answer»

`Na_2 SO_4. 5H_2O`
`Na_2SO_4. 7H_2O`
`Na_2SO_4 . 2H_2O`
`Na_2SO_4. 10 H_2O`

Solution :Molecular MASS of `Na_2SO_4 = 2 xx 23 + 32 + 4 xx 16 = 142`
A crystalline salt on becoming anhydrous loses 55.9% by mass .
44.1 g of anhydrous salt contain `H_2O` = 55.9
142g of anhydrous salt contain `H_2O`
` = (55.9)/(44.1) xx 142 = 180 g `
No. of molecules ` = 180/80 = 10`


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