[tex]50g[/tex] [tex]of[/tex] [tex] C_2H_4O_2[/tex] [tex]in[/tex] [tex] 200g[/tex] [tex]H_2O[/tex]
so:
[tex] \frac{50}{200+50}+100\%= \frac{50*100}{250}\%=20\%[/tex]
[tex]MW of acid = 2*C+4*H+2*O = 2*12+4*1+2*16=[/tex]
[tex]=24+4+32=60g/mol[/tex]
so:
[tex]\frac{50g}{60g/mol}\approx0.83moles[/tex]
it means that
in [tex]50g[/tex] of acid there is [tex]\approx0.83[/tex]moles of acid
[tex]MW of H_2O = 2*H+O=2*1+16=2+16=18g/mol[/tex]
so:
[tex]\frac{200g}{18g/mol}\approx11.11moles[/tex]
it means that:
in [tex]200g[/tex] of water there is [tex]\approx11.11[/tex]moles of water
therefore:
[tex] \frac{0.83mol}{11.11mol+0.83mol}= \frac{0.83mol}{11.94mol}=0.069[/tex]
So your answers are:
[tex]20\%[/tex]
and the mole fraction is:
[tex]0.069[/tex]