26.8 g of Na_2SO_4.xH_2O gave 12.6 g of water on heating. Determine the value of x in the compound using mole concept.

26.8 g of Na_2SO_4.xH_2O gave 12.6 g of water on heating. Determine th

1.	26.8 g of Na_2SO_4.xH_2O gave 12.6 g of water on heating. Determine the value of x in the compound using mole concept.
Answer» Solution :Weight of hydrated salt `Na_2SO_4.xH_2O = 26.8 g` Weight of water given by it = 12.6 g `therefore` Weight of anhydrous salt `Na_2SO_4 = 26.8 - 12.6 = 14.2g` Gram molecular mass of `Na_2SO_4 = (2 xx 22.99) + 32.06 + (4 xx 16.0) = 142.04 g` `therefore` Number of moles of `Na_2SO_4 = 142 04/(142.04) = 0.0999` and number of moles of `H_(2)O`associated with it `12.6/18.016` `therefore 0.0999` moles of `Na_2SO_4` ATTACH moles of water = `0.699 , therefore` 1 MOLE of `Na_2SO_4` will attach moles of water `=0.699/0.0999 xx 1` = 6.99 =7, Hence, x=7