Ncert Exercises & Solutions

2.29 Nalorphene (C₁₉H₂₁NO₃), similar to morphine, is used to combat withdrawal symptoms in narcotic users. Dose of nalorphene generally given is 1.5 mg. Calculate the mass of 1.5 – 10^–3 m aqueous solution required for the above dose.

The molar mass of nalorphene (C₁₉H₂₁NO₃) is given as:

$19 \times 12 + 21 \times 1 + 1 \times 14 + 3 \times 16 = 311 g {mol}^{- 1}$

In 1.5 × 10⁻³m aqueous solution of nalorphene,

1 kg (1000 g) of water contains 1.5 × 10−3 mol $= 1.5 \times 10^{- 3} \times 311 g$

$= 0.4665 g$

Therefore, total mass of the solution $= (1000 + 0.4665) g$

$= 1000.4665 g$

This implies that the mass of the solution containing 0.4665 g of nalorphene is 1000.4665 g.

Therefore, mass of the solution containing 1.5 mg of nalorphene is:

$\frac{1000.4665 \times 1.5 \times 10^{- 3}}{0.4665} g$

$= 3.22 g$

Hence, the mass of aqueous solution required is 3.22 g.

Note: There is a slight variation in this answer and the one given in the NCERT textbook.

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