Consider the following pairs of solution which will be isotonic at the same temperature. The number of pairs of solutions is/are _____ A. 1 M aq. NaCl and 2 M aq. Urea B. 1 M aq. \(\mathrm{CaCl}_{2}\) and 1.5 M aq. KCl C. 1.5 M aq. \(\mathrm{AlCl}_{3}\) and 2 M aq. \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) D. 2.5 M aq. KCl and 1 M aq. \(\mathrm{Al}_{2}(\mathrm{SO}_{4})_{3}\)

JEE Main · 2023 · 06 Apr 2023 · Shift 2 · Solutions

Consider the following pairs of solution which will be isotonic at the same temperature. The number of pairs of solutions is/are _____
A. 1 M aq. NaCl and 2 M aq. Urea
B. 1 M aq.

CaCl_{2}

and 1.5 M aq. KCl
C. 1.5 M aq.

AlCl_{3}

and 2 M aq.

Na_{2} SO_{4}

D. 2.5 M aq. KCl and 1 M aq.

Al_{2} (SO_{4})_{3}

Answer: 4

Solution

Osmotic pressure is set by the total concentration of dissolved particles,

π = i C R T

, so two solutions are isotonic when their products

i C

are equal. Sodium chloride gives

i C = 2 \times 1 = 2

and urea

1 \times 2 = 2

; calcium chloride gives

3 \times 1 = 3

and potassium chloride

2 \times 1.5 = 3

. Aluminium chloride gives

4 \times 1.5 = 6

and sodium sulphate

3 \times 2 = 6

; potassium chloride gives

2 \times 2.5 = 5

and aluminium sulphate

5 \times 1 = 5

. Each of the four pairs has matching

i C

values, so the number of isotonic pairs is 4.

JEE Main · 2023 · 06 Apr 2023 · Shift 2 · Integer answer

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JEE Main · 2023 · 06 Apr 2023 · Shift 2 · Solutions

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