1.

The crystalline salt `Na_(2)SO_(4)` on heating loses 55.9 % of its weight. The formula of the crystalline salt is :A. `Na_(2)SO_(4).5H_(2)O`B. `Na_(2)SO_(4).7H_(2)O`C. `Na_(2)SO_(4).2H_(2)O`D. `Na_(2)SO_(4).10H_(2)O`

Answer» Correct Answer - D
`("Molar mass of "Na_(2)SO_(4).xH_+N578(2)O)/("Molar mass of "Na_(2)SO_(4))=(100)/(44.1)`
`((142+18x)u)/(142u)=(100)/(44.1)`
`(142 + 18 x)u = (100)/(44.1) xx(142 u) = 321.99u`
`18 x = 321.99 - 142 = 179.99`
`x = (179.99)/(18)=10`
`:.` Formula of crystalline salt `= Na_(2)SO_(4).10H_(2)O`.


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