20g*9.8g=1.96g 2NaOH+H2SO4==Na2SO4+2H2O80 98 142x 1.96g y80/x=98/1.96g=142/yx=1.6gy=2.84g[1]氢氧化钠溶液中溶质的质量分数 1.6g/20g*100%=8% [2]反应后溶液中溶质的质量分数 2.84g/(20g+9.8g)*100%=9.53%