-Gọi x là số mol H2SO4 61,2%\(\rightarrow m_{dd\left(bđ\right)}=\dfrac{98x.100}{61,2}\left(g\right)\)
\(n_{H_2SO_4\left(tt\right)}=n_{SO_3}=\dfrac{40}{80}=0,5\left(mol\right)\)
\(\rightarrow n_{H_2SO_4\left(sau\right)}=x+0,5\left(mol\right)\)
\(\rightarrow m_{dd\left(sau\right)}=\dfrac{98\left(x+0,5\right).100}{73,5}\left(g\right)\)
Ta có: \(\rightarrow m_{dd\left(sau\right)}=m_{dd\left(bđ\right)}+m_{SO_3}\)
\(\Leftrightarrow\)\(\dfrac{98\left(x+0,5\right).100}{73,5}=\dfrac{98x.100}{61,2}+40\)
Giải ra x\(\approx1\left(mol\right)\)
\(\rightarrow m_{dd\left(bđ\right)}=\dfrac{98.1.100}{61,2}=160,13\left(g\right)\)