5 g of Na_2SO_4 was dissolved in x g of H_2 | vedclass

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(C) Molar mass of $Na_2SO_4 = (2 	imes 23) + 32 + (4 	imes 16) = 142 \ g \ mol^{-1}$.Van't Hoff factor $(i)$ for $Na_2SO_4 	o 2Na^+ + SO_4^{2-}$ is

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(C) Molar mass of $Na_2SO_4 = (2 	imes 23) + 32 + (4 	imes 16) = 142 \ g \ mol^{-1}$.Van't Hoff factor $(i)$ for $Na_2SO_4 	o 2Na^+ + SO_4^{2-}$ is $i = 1 + (n-1)\alpha$,where $n=3$ and $\alpha = 0.815$.$i = 1 + (3-1) 	imes 0.815 = 1 + 2 	imes 0.815 = 2.63$.Freezing point depression formula: $\Delta T_f = i 	imes K_f 	imes m$.$3.82 = 2.63 	imes 1.86 	imes \left( \frac{5 / 142}{x / 1000} ight)$.$3.82 = 2.63 	imes 1.86 	imes \frac{5000}{142 	imes x}$.$x = \frac{2.63 	imes 1.86 	imes 5000}{142 	imes 3.82} \approx 45.07 \ g$.

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