A student placed a mixture of BaO and CaO of combined mass 4.88g in a flask containing carbon dioxide gas....?

Question

After the reacitons were complete, she found that 0.0356 moles of CO2 had reacted. Calculate the mass of BaO and CaO reactants.
CaO+CO2-->CaCO3
BaO+CO2-->BaCO3

Answer 1

Mass of CaO = M(CaO) plus mass BaO =M(BaO) = 4.88g

M(CaO) + M(BaO) = 4.88

Moles(CaO) + Moles(BaO) = 0.0356

multiply bottom equation by mm(CaO) (molecular mass of CaO):

Moles(CaO)*mm(CaO) + Moles(BaO)*mm(CaO) = 0.0356*mm(CaO)

but Moles(CaO)*mm(CaO) = M(CaO):

M(CaO) + Moles(BaO)*mm(CaO) = 0.0356*mm(CaO)

M(CaO) + M(BaO) = 4.88 (the first equ repeated here)

Subtract the eqs above [M(CaO) cancels out]:

Moles(BaO)*mm(CaO) - M(BaO) = 0.0356*mm(CaO) - 4.88

Moles(BaO) = M(BaO)/mm(BaO)

M(BaO)*mm(CaO)/mm(baO) - M(BaO) = 0.0356*mm(CaO) - 4.88

M(BaO)*[mm(CaO)/mm(BaO) - 1] = 0.0356*mm(CaO) - 4.88

M(BaO) = [0.0356*mm(CaO) - 4.88] / [mm(CaO)/mm(BaO) - 1]

Look up or calculate molecular masses mm(CaO) and mm(BaO) and compute the mass of BaO, M(BaO).

When you get that, subtract from 4.88 to get M(CaO)