5 g of Na 2 SO 4 was dissolved in x g of H 2 O . The change in freezing point was found to be 3 .82 o C . If Na 2 SO 4 is 81 . 5 % ionised, the value of x ( K f for water = 1 .86 o C kg mol - 1 ) is approximately: (molar mass of S = 32 g mol - 1 and that of Na = 23 g mol - 1 )

Question

5 g of Na 2 SO 4 was dissolved in x g of H 2 O . The change in freezing point was found to be 3 .82 o C . If Na 2 SO 4 is 81 . 5 % ionised, the value of x ( K f for water = 1 .86 o C kg mol - 1 ) is approximately: (molar mass of S = 32 g mol - 1 and that of Na = 23 g mol - 1 ), 25 g, 65 g, 15 g, 45 g

MARKS App · Accepted Answer

Na 2 SO 4 → 2 Na + + SO 4 2 - i = 1 + 3 - 1 0 .815 = 2 .63 3 .82 = 1 .86 × 2 .63 × 5 × 1000 142 × x ∴ x = 1 .86 × 2 .63 × 5000 142 × 3 .82 = 45 gm

Search any question & find its solution

Looking for more such questions to practice?