A 2.85-g sample of an unknown chlorofluorocarbon is decomposed and produces 564 mL of chlorine gas (Cl2) at a pressure of 752 mmHg and a temperature of 298 K. What is the percent chlorine (by mass) in the unknown chlorofluorocarbon

Answer :

Eduard22sly

The percentage of chlorine by mass in the unknown chlorofluorocarbon is 56.8%

We'll begin by calculating the number of mole of Cl₂ produced using the ideal gas equation as illustrated below:

  • Volume (V) = 564 mL = 564 / 1000 = 0.564 L
  • Pressure (P) = 752 mmHg = 752 / 760 = 0.989 atm
  • Temperature (T) = 298 K
  • Gas constant (R) = 0.0821 atm.L/Kmol
  • Number of mole (n) =?

PV = nRT

0.989 × 0.564 = n × 0.0821 × 298

0.557796 = n × 24.4658

Divide both side by 24.4658

n = 0.557796 / 24.4658

n = 0.0228 mole

Next, we shall determine the mass of 0.0228 mole of Cl₂

  • Mole = 0.0228 mole
  • Molar mass of Cl₂ = 2 × 35.5 = 71 g/mol
  • Mass of Cl₂ =?

Mass = mole × molar mass

Mass of Cl₂ = 0.0228 × 71

Mass of Cl₂ = 1.62 g

Finally, we shall determine the percentage of chlorine in the unknown chlorofluorocarbon.

  • Mass of Cl₂ = 1.62 g
  • Mass of compound = 2.85 g
  • Percentage of chlorine =?

Percentage = (mass / total mass) × 100

Percentage of chlorine =(1.62 / 2.85) × 100

Percentage of chlorine = 56.8%

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