The vapour pressure of water at `20^@C` is 17.5 mm Hg. If 18 g of glucose `(C_6H_(12)O_6)` is added to 178.2 g of water at `20 ^@C`, the vapour pressure of the resulting solution will be

Options

A. 17.325 mm Hg
B. 17.675 mm Hg
C. 15.750 mm Hg
D. 16.500 mm Hg

Answer

A

Explanation

In solution containing non-volatile solute, pressure is directly proportional to its mole fraction.
`P_("solution")` = vapour pressure of its pure component `xx` mole fraction in solution
`:. P_(sol)= P^@X_("solvent")`
Let A be the solute and B the solvent
`:. X_B = n_B/(n_A+n_B)=((178.2)/18)/(18/180+(178.2)/18) implies X_B = 9.9/10 = 0.99`
Now `P_("solution") = P^@X_("solvent") = 17.5 xx 0.99`
`P_("solution") = 17.32 mm Hg`