(1)设稀硫酸的溶质质量为x,Na2CO3+H2SO4=Na2SO4+H2O+CO2↑98 44x 0.22g∴98:44=x:0.22g,解之得:x=0.49g,稀硫酸的溶质质量分数为: 0.49g 50g ×100%=0.98%.(2)过碳酸钠的化学式为:2Na2CO3?3H2O2.故答案为:(1)0.98%;(2)2Na2CO3?3H2O2.