Homework Help: chemistry

Posted by b on Wednesday, May 9, 2012 at 10:31pm.

A .500 g sample of impure CaO (a solid) is added to 50.0 mL of 0.100 M HCl. The excess HCl is titrated by 5.00 mL of .125 M NaOH. What is the percentage of CaO in the sample?

chemistry - DrBob222, Wednesday, May 9, 2012 at 11:14pm
CaO + 2HCl ==> CaCl2 + H2O

mols HCl to start = M x L = ?
mols HCl excess = M x L = 0.125 M x 0.005 L = ?
Subtract. The difference is mols HCl used by the CaO.
mols CaO = 1/2 mols HCl (the coefficients tell you that).
g CaO = mols x molar mass
%CaO = (mass CaO/ mass sample)*100 = ?

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