A mixture of sodium hydroxide, NaOH(s) and benzoic acid, HC7H5O2(s), consists of a total of 0.50 moles. This mixture is dissolved in 1.0 L of water and the pH of the resulting solution is determined to be 12.52. Find the mole fraction of benzoic acid in the initial mixture.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm

i think it's letter a.