设100g稀盐酸中溶质的质量是x.
CaCO3+2HCl=CaCl2+H2O+CO2↑
73 44
x 2.2g
73/x=44/2.2
x=3.65g
稀盐酸的质量分数是3.65/100*100%=3.65%
答：所用稀盐酸的质量分数是3.65%