解:MCO3+2HCl=MCl2+H2O+CO2↑n(MCO3)=n(CO2)=4.48L/22.4L/mol=0.2molM(MCO3)=39.4g/0.2mol=197g/molM的相对原子质量197-60=137,为钡元素。滤液为NaHCO3稀释后取出25mlNaHCO3+HCl=NaCl+H2O+CO2↑n(NaHCO3)=n(HCl)=n(CO2)=1.12L/22.4L/mol=0.05molc(HCl)=0.05mol/0.02L=2.5mol/L