a) 2CH3-COOH + Mg --> (CH3-COO)2Mg + H2↑
2CH3-COOH + MgO --> (CH3-COO)2Mg + H2O
2CH3-COOH + MgCO3 --> (CH3-COO)2Mg + CO2 + H2O
b) MCH3-COO⁻Na⁺=2AC+3AH+2AO+ANa=2*12+3*1+2*16+23=82g/mol
%C=mC/M*100=24/82*100=29.268
%H=mH/M*100=3/82*100=3.658
%Na=mNa/M*100=23/82*100=28