Numerical answer type, answer in atm, tolerance 0.002.
Answer: 0.835 atm
If all the water vaporised: n=0.10/18=0.00556 mol, P=1.00.00556×0.0821×300=0.137 atm, which exceeds the vapour pressure. So liquid water remains and pHX2O=0.035 atm. Total =0.800+0.035=0.835 atm.