JEE Main · 2020 · 03 Sep 2020 · Shift 2 · Solutions

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250 cm^{3}

of an aqueous solution containing 0.73 g of a protein A is isotonic with one litre of another aqueous solution containing 1.65 g of a protein B , at 298 K , the ratio of the molecular masses of

A

and

B

is ____

\times 1 0^{- 2}

(to the nearest integer).

Answer: 177

Solution

Isotonic solutions have equal osmotic pressures, and for these protein solutions the van't Hoff factor is

1

, so their molar concentrations are equal:

\frac{0.73}{M _{A} \times 0.250} = \frac{1.65}{M _{B} \times 1}

. Rearranging,

\frac{M _{A}}{M _{B}} = \frac{0.73 \times 1}{1.65 \times 0.250} = \frac{2.92}{1.65} \approx 1.77

. Expressed as the question asks, this ratio is

177 \times 1 0^{- 2}

JEE Main · 2020 · 03 Sep 2020 · Shift 2 · Integer answer

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