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

Explanation

`0.25` molar aqueous solution means that
Moles of urea `= 0.25 ` mole
Mass of solvent (water) `=1 kg = 1000 kg`
Molar mass of urea `= 14 + 2 + 12 + 16 + 14 + 2 =60 g mol ^(-1)`
`therefore 0.25` mole of urea `= 60xx0.25 ` mole = 15 g
Total mass of the solution `= 1000 + 15 g = 1015 g = 1. 015g`
Thus, `1.015` kg of solution contain urea = 15 h
`therefore 2.5 kg ` of solution will require urea `= (15)/(1.015) xx 2.5 kg =37g`