What is the value of the mass of urea (NH_(2)CONH_(2)) required to make 2.5 kg, 0.25 molal aqueous solution?

Calculate the mass of urea (NH_(2)CONH_(2)) required in making 2.5 kg of 0.25 molal aqueous solution.

Mole fraction of a solute in 2.5 molal aqueous solution is

25 ml of the given HCl solution requires 30 mL of 0.1M sodium carbonate solution. What is the volume of this HCl solution required to titrate 30 mL of 0.2M aqueous NaOH solution ?