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.

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.

Solution:

Sol. Molecular mass of nalorphene (C₁₉H₂₁NO₃)

= (12 × 19) + 1 × 21 + 14 × 1 + 16 × 3

= 311 g mol^-1

Molality of solution = 1.5 × 10^-3 m

 

Let take mass of water = 1kg = 1000g

Then required moles of solute = 1.5 × 10^-3 moles

Mass of  1.5 × 10^-3 moles of nalorphene  = number of moles x molar mass

                                                      =  1.5 × 10^-3 × 311 = 0.467 g

  Mass of total solution = 1000 g + 0.467 g  = 1000.467 g

To convert 1.5 g of nalorphene in to g divide by 1000 we get

1.5 mg / 1000  = 0.0015 g

Thus, 0.467 g mass of nalorphene contain by      = 1000.467 g solution

  for 0.0015 g mass of nalorphene contain by       = 1000.467 × 0.0015/0.467

 = 3.21 g.