The percentage labelling (mixture of `H_(2)SO_(4)` and `SO_(3))` refers to the total mass of pure `H_(2)SO_(4)`. The total amount of `H_(2)SO_(4)` found after adding calculated amount of water to `100 g` oleum is the percentage labelling of oleum. The higher the percentage lebeling of oleum higher is the amount of free `SO_(3)` in the oleum sample.
`100 g` sample of '149%' oleum was taken and calculated amount of `H_(2)O` was added to make `H_(2)SO_(4)`.`500 mL` solution of `x MKOH` solution is required to neutralize the solution. The value of `x` is.