Pre-laboratory excercises

Question

The thermol decompostion of calcium carbonate produces two by-products, calcium oxide (also known as quicklime) and carbon dioxide. Calculate the volume of carbon dioxide produced at STP from the decompostition of 231 grams of calcium carbonate.

Answer 1

Th chemical equation is

CaCO₃ → CaO+ CO₂↑

 

We are given 231 grams of CaCO₃, and need to change this to moles.

 

Number of moles = grams/ molar mass ≈ 231 grams/ (40 +12 + 48) = 2.31 moles

 

From the mole ratios (look at the coefficients) of the substances in the balanced equation, the decomposition of 1 mole of CaCO₃ produces 1 mole of CaO and 1 mole of CO_2.

 

Therefore, 2.31 moles of CaCO₃ produces 2.31 moles of CO2.

 

At STP, 1 mole of a gas occupy 22.4 liters volume.

 

What is the volume of gas occupied by 2.31 moles?