\(SO_3+H_2O\rightarrow H_2SO_4\\ m_{H_2SO_4\left(tăng\right)}=\dfrac{98}{80}m=\dfrac{49}{40}m=1,225m\left(g\right)\\ m_{H_2SO_4\left(dd.14,7\%\right)}=14,7.200=29,4\left(g\right)\\ Ta.có:C\%_{ddH_2SO_4\left(cuối\right)}=20\%\\ \Leftrightarrow\dfrac{29,4+1,225m}{m+200}.100\%=20\%\\ m\approx10,3415\left(g\right)\)