2.29    Nalorphene (C_{19}H_{21}NO_{3}), 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.

Answers (1)

We are given with molality of the solution, so we need to find the moles of Nalorphene.

Molar mass of nalorphene =  19(12) + 21(1)  + 1(14) + 3(16)  =  311u.

So moles of nalorphene :

                                             \frac{1.5\times10^{-3}}{311} = 4.82\times 10^{-6}\ moles

Molality :

                                                          = \frac{No.\ of\ moles\ of\ solute}{Mass\ of\ solvent\ in\ kg}

or                                                       1.5\times 10^{-3} = \frac{4.82\times 10^{-6}}{w}

or                                                               w = 3.2\times 10^{-3}\ Kg

So the required weight of water is 3.2 g.

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