Question

Dissolving 3.00 g of an impure sample of calcium carbonate in hydrochloric acid produced 0.656 L
of carbon dioxide (measured at 20.0°C and 792 mmHg). Calculate the percent by mass of calcium
carbonate in the sample. State any assumptions.

Answer 1

Answer on Question #40918, Chemistry, Other

Question

Dissolving 3.00 g of an impure sample of calcium carbonate in hydrochloric acid produced 0.656 L of carbon dioxide (measured at 20.0°C and 792 mmHg). Calculate the percent by mass of calcium carbonate in the sample. State any assumptions.

Answer

The assumptions are:

- calcium carbonate was dissolved to the full extent and amount of CO₂ released was proportional to the amount of CaCO₃

- the sample did not contain any other compounds that released CO₂ or reacted with CO₂

PV=nRT

n=PV/RT

P=792 mmHg = 792/760 atm = 1.04 atm

T = 20 + 273 = 293 K

R = 8.314 J/(K*mol) = 0.082 (L*atm)*(K*mol)

n(CO₂) = (1.04 atm * 0.656 L)/(0.082 (L*atm)*(K*mol)*293 K) = 0.0284 mol

CaCO₃ + 2HCl = CaCl₂ + CO₂ + H₂O

n(CaCO₃) = n(CO₂)

m(CaCO₃) = n(CaCO₃)*M(CaCO₃) = 0.0284 mol* 100 g/mol = 2.84 g

w(CaCO₃) = (2.84g / 3.00 g)*100 % = 94.7 %

Answer: 94.7 %.