Question

The sedative Demerol hydrochloride has the formula CisH22CINO2. Calculate the mass (g) of a 0.028 mole sample of the compound. According to the equation: Zn(s) + 2HCl(aq) ----> H2(g) + ZnCl(aq), calculate the volume (L) of H2 gas that can be formed at 25 °C and a pressure of 854 mmHg when 25.0 g of Zn is used in the reaction.

Answer 1

1. Molar mass of Demerol hydrochloride(C₁₅H₂₂ClNO₂)

=15 x Molar mass of C+22 x Molar mass of H+ Molar mass of Cl+ Molar mass of N+2 x Molar mass of O

=15 x 12 g/mol+22 x 1 g/mol+35.5 g/mol+14 g/mol+2 x 16 g/mol

=180 g/mol+22 g/mol+35.5 g/mol+14 g/mol+32 g/mol

=283.5 g/mol

Mass of 0.028 mol of the sample=Number of moles x Molar mass=0.028 mol x 283.5 g/mol=7.938 g

2. Molar mass of Zn=65.4 g

Number of moles of Zn=Given mass/Molar mass

=25.0 g/65.4 g/mol=0.38 mol

As per the balanced chemical reaction

1 mol Zn forms 1 mol H₂

So 0.38 mol Zn should form 0.38 mol H₂

Now substitute P=Pressure=854 mm Hg=854 mm Hg/760 mm Hg/atm (1 atm=760 mm Hg)

n=Number of moles=0.38 mol

R=0.0821 Latm/molK

T=Temperature=T=25°C=25+273 K=298 K (0°C=273 K)

in PV=nRT (where V=Volume)

(854 mm Hg/760 mm Hg/atm) x V=0.38 mol x 0.0821 Latm/molK x 298 K

V=(0.38 mol x 0.821 Latm/molK x 298 K)/(854 mm Hv/760 mm Hg/atm)=8.27 L

So volume of H₂ gas formed =8.27 L