设稀盐酸的溶质质量为x.
NaOH+HCl=NaCl+H2O
40 36.5
40g*10% x
40/4=36.5/x
x=3.65g
稀盐酸的溶质质量分数是3.65/36.5*100%=10%
答:稀盐酸的溶质质量分数是10%