What are the mole fractions of "water, ethanol, acetic acid," in a 25%:25%:50% mixture by mass?

1 Answer
Jun 14, 2017

We assume a mass of 100*g.....and come up mole fractions of chi_(H_2O)=0.503; chi_("EtOH")=0.196; chi_("HOAc")=0.301.....

Explanation:

We assume a mass of 100*g.....and work out the molar quantities on that basis........

"Moles of water"=(25*g)/(18.01*g*mol^-1)=1.39*mol

"Moles of ethanol"=(25*g)/(46.07*g*mol^-1)=0.543*mol

"Moles of acetic acid"=(50*g)/(60.05*g*mol^-1)=0.833*mol

And thus...........

chi_(H_2O)=(1.39*mol)/((1.39+0.543+0.833)*mol)=0.503

chi_("EtOH")=(0.543*mol)/((1.39+0.543+0.833)*mol)=0.196

chi_("HOAc")=(1.39*mol)/((1.39+0.543+0.833)*mol)=0.301

And we note that chi_(H_2O)+chi_"EtOH"+chi_"HOAc"=1.00, as is required for a Sigman_i where n_i are the individual molar quantities.