5g of Na _ 2 SO _ 4 was dissolved in xg 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 Ckg mol ^ - 1 ) is

Correct answer: D. 45g 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) = 45gm

JEE Main 20178 AprilOnline

Exam: JEE Main
Year: 2017
Date: 8 April
Mode: Online
Subject: Chemistry
Chapter: Solutions

JEE Main 2017 · 8 April · Online · Chemistry · Solutions

5g of Na _ 2 SO _ 4 was dissolved in xg of H _ 2 O . The change in...

5g

{Na}_{2}{SO}_{4}

was dissolved in

xg

{H}_{2}O

. The change in freezing point was found to be

3{.82}^{o}C

. If

{Na}_{2}{SO}_{4}

81 . 5 %

ionised, the value of

x

(

{K}_{f}

for water

= 1{.86}^{o}Ckg{mol}^{- 1}

) is approximately:

(molar mass of

S = 32g{mol}^{- 1}

and that of

Na = 23g{mol}^{- 1}

)

Options

A $25g$
B $65g$
C $15g$
D $45g$

Correct answer

D. $45g$

Step-by-step solution

{Na}_{2}{SO}_{4} \to 2{Na}^{+} + {SO}_{4}^{2 -}

i = 1 + \left(3 - 1\right)0 .815 = 2 .63

3 .82 = 1 .86 \times 2 .63 \times \dfrac{5 \times 1000}{142 \times x}

∴ x = \dfrac{1 .86 \times 2 .63 \times 5000}{142 \times 3 .82}

= 45gm

Practice Solutions on Quantrex Academy →

More from Solutions

In a solvent S , a compound B is partially dissociated into C and D as given below: B… JEE Advanced 2026 Passage: Two volatile liquids A and B form an ideal solution. Consider a 5 molal solution… JEE Advanced 2026 Passage: Two volatile liquids A and B form an ideal solution. Consider a 5 molal solution… JEE Advanced 2026 Given below are two statements: Given: Molar mass of C, H, O, Cl are 12, 1, 16 and 35.5 g… JEE Main 2026 Which of the following statements are not correct? A. For water, magnitude of K_b is more… JEE Main 2026 Given below are two statements : Statement I : H _2 O molecules move from the chamber 1… JEE Main 2026 When 0.25 moles of a non-volatile, non-ionizable solute was dissolved in 1 mole of a… JEE Main 2026 20 g hemoglobin in a 1 L aqueous solution (A) at 300 K is separated from pure water by… JEE Main 2026 Full Solutions list All JEE Main PYQs