berapa garam urea (CO(NH2)2) yang harus dilarutkan kedalam 200 ml air (p air = 1 g/ml ) agar kemolalan larutannya 0,2 m. (Ar C = 12 ; Ar O= 16 ; Ar N = 23 ; Ar

V air = 200 mL
mj air = 1 gr/mL
molal urea = 0,2 molal
massa urea = .... ?

Mr urea = Ar C + Ar O + 2 Ar N + 4 Ar H
= 12 + 16 + 2(14) + 4(1)
= 60

m air = V air × mj air
= 200 mL × 1 gr/mL
= 200 gram

molal = ( massa urea / Mr ) × ( 1000 / m air )
massa urea = molal × Mr × m air / 1000
= 0,2 × 60 × 200 gr / 1000
= 2,4 gram