JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Solutions

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20 g hemoglobin in a 1 L aqueous solution (A) at 300 K is separated from pure water by semi permeable membrane. At equilibrium the height of solution in a tube dipped in a solution (A) is found to be 80.0 mm higher than the tube dipped in water.

The molar mass of hemoglobin is ____ kg mol⁻¹. (Nearest integer)
(Given : g=10 ms⁻², R=8.3 kPa dm³ K⁻¹ mol⁻¹, density of solution =1000 kg m⁻³)

Answer: 62

Solution

The osmotic pressure equals the hydrostatic pressure of the raised column,

π = ρ g h = 1000 \times 10 \times 0.080 = 800 Pa = 0.8 kPa

. For a dilute solution

π = C R T = \frac{w}{M V} R T

, with

w = 20 g

V = 1 d m^{3}

R = 8.3 kPa d m^{3} K^{- 1} mo l^{- 1}

and

T = 300 K

. Solving for the molar mass,

M = \frac{w R T}{π V} = \frac{20 \times 8.3 \times 300}{0.8 \times 1} = 62250 g mo l^{- 1}

. The molar mass of haemoglobin is

62 kg mo l^{- 1}

JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Integer answer

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JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Solutions

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