chemistry question pls help i am struggling

Question

A mixture of solid calcium oxide, CaO, and solid barium oxide, BaO, weighing 4.791 g is added to a 2.00 L flask containing carbon dioxide, CO2, at 30 ∘C. The CaO and BaO react completely with the carbon dioxide gas to form solid CaCO3 and BaCO3, respectively. Calculate the moles of CO2 consumed by the reaction if the initial pressure of CO2 gas was 0.852 atm and the final pressure of CO2 gas is 0.261 atm.

1. mols of CO2:
2. What is the mass percentage of CaO in the solid mixture?
3. mass percent CaO:
4. What is the mass percentage of BaO in the solid mixture?
5. mass percent BaO:

Answer 1

CaO(s) + CO2(g) ==> CaCO3(s)

BaO(s) + CO2(g) ==> BaCO3(s)

1). moles of CO2 consumed:

PV = nRT

initial moles present = n = PV/RT = (0.852 atm)(2.00L) / (0.0821)(303K) = 0.0685 mols CO2

final moles present = n = PV/RT = (0.261 atm)(2.00L) / (0.0821)(303K) = 0.02098 mols CO2

moles of CO2 consumed = 0.0685 - 0.0210 = 0.04752 mols CO2

2-5).

CaO + BaO + 2CO2 ==> CaCO3 + BaCO3

0.04752 mols CO2 x 1 mol CaO / mol 2CO2 = 0.02376 mols CaO

0.04752 mols CO2 x 1 mol BaO / mol 2CO2 = 0.02376 mols BaO

molar mass CaO = 56.1 g/mol

molar mass BaO = 153 g/mol

mass CaO = 0.02376 mols x 56.1 g/mol = 1.333 g

mass BaO = 0.02376 mols x 153 g/mol = 3.635 g

Not sure why these don't add up to the original mass of 4.791 g, as it should.

If you use the original mass of 4.791 g, then mass % is ...

%CaO = 27.8%

%BaO = 75.9% (total .100%)

If you use the mass of 1.333 g + 3.635 g = 4.968 g, then mass % is...

%CaO = 26.8%

%BaO = 73.2%

(NOTE: maybe someone will respond and explain why the masses don't add up to the original mass of the sample)