0.15 M solution means than 0.15 mole of benzoic acid is dissolved in 1L of solution.

Molar mass of `C_(6)H_(5)COOH`

`=12xx6+5+12+2xx16+1=122 " g mol"^(-1)`

`therefore 0.15 " mol of " C_(6)H_(5)COOH=0.15xx122=18.3 g`

Thus, 1L or 1000 mL of solution contain

`=18.3 " g of " C_(6)H_(5)COOH`

` therefore 250 mL` of the solution will contain

`(18.3)/(1000)xx250=4.575 " g of " C_(6)H_(5)COOH`.