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Question
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.
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Solution
Given: m = 1.5 × 10−3
The molar mass of nalorphene (C19H21NO3) = 19 × 12 + 21 × 1 + 1 × 14 + 3 × 16
= 311 g mol−1
In a 1.5 × 10−3 m aqueous solution of nalorphene,
1 kg (1000 g) of water contains 1.5 × 10−3 mol.
= 1.5 × 10−3 × 311 g
= 0.467 g
= 467 mg
∴ Total mass of the solution = (1000 + 0.467) g
= 1000.467 g
Thus, for 467 mg of nalorphene, the solution required is 1000.467 g.
∴ The mass of the solution containing 1.5 mg of nalorphene = `1000.467/467 xx 1.5`
= 3.21 g
Hence, the mass of the aqueous solution required is 3.21 g.
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