Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and PQ_ 2 . When 1 g of PQ is dissolved in 50 g of solvent ^ A^ , Δ T_ b was 1.176 K while when 1 g of PQ_ 2 is dissolved in 50 g of solvent ^

Correct answer: C. 25,60 Using Δ T_b = K_b × (w)/(M) × (1000)/(W) For PQ: 1.176 = 5 × 1 M_ PQ × (1000)/(50) = 100 M_ PQ M_ PQ = (100)/(1.176) = 85 g/mol For PQ_2 : 0.689 = 100 M_ PQ_2 M_ PQ_2 = (100)/(0.689) = 145 g/mol P + Q = 85 ... (i) P + 2Q = 145 ... (ii) Subtracting: Q = 60 g/mol From (i): P = 85 - 60 = 25 g/mol

JEE Main 202621 JanuaryMorning Shift

Exam: JEE Main
Year: 2026
Date: 21 January
Shift: Morning Shift
Subject: Chemistry
Chapter: Solutions

JEE Main 2026 · 21 January · Morning Shift · Chemistry · Solutions

Elements P and Q form two types of non-volatile, non-ionizable...

Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and

\mathrm{PQ}_{2}

. When 1 g of PQ is dissolved in 50 g of solvent

{ }^{\prime} \mathrm{A}^{\prime}, \Delta \mathrm{T}_{\mathrm{b}}

was 1.176 K while when 1 g of

\mathrm{PQ}_{2}

is dissolved in 50 g of solvent

{ }^{\prime} \mathrm{A}^{\prime}, \Delta \mathrm{T}_{\mathrm{b}}

was 0.689 K. (

\mathrm{K}_{\mathrm{b}}

of '

\mathrm{A}^{\prime}=5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}

). The molar masses of elements P and Q (in

\mathrm{g} \mathrm{mol}^{-1}

) respectively, are :

Options

A $70,110$
B $65,145$
C $25,60$
D $60,25$

Correct answer

C. $25,60$

Step-by-step solution

Using

\Delta T_b = K_b \times \frac{w}{M} \times \frac{1000}{W}

For PQ:

1.176 = 5 \times \frac{1}{M_{PQ}} \times \frac{1000}{50} = \frac{100}{M_{PQ}}

M_{PQ} = \frac{100}{1.176} = 85

g/mol
For

PQ_2

0.689 = \frac{100}{M_{PQ_2}}

M_{PQ_2} = \frac{100}{0.689} = 145

g/mol

P + Q = 85

... (i)

P + 2Q = 145

... (ii)
Subtracting:

Q = 60

g/mol
From (i):

P = 85 - 60 = 25

g/mol

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