Question

14. What is the vapor pressure in mmHg of a solution of a solution that contains 10.0 g of urea, CHAN20, in 150.0 g of water at 45.0 "C. The vapor pressure of water at 45.0°C is 71.93 mmHg and urea is a nonvolatile solute. 15. What is the freezing point in °C for the above problem? For water, Kr-1.86 °C/m. 16. The van't Hoff factor for KClisi = 1.85. What is the boiling point of a 0.75 m solution of KCI in water? For water Kb = 0.51 °C/m.

Answer 1

15 Depression in when a Solute dissolved point of the pure solvent. According freezing point and Roulto law non-volatile, non-elee trolyte in a solution, the freezing solution decreases than the to Roulty laws ATG = kq xm ma molality of solution moles of solute mass of Solvent Kf = cryoscopic constant in mole (kg atf = Decrease intemperat = (Ts - Tf) = freezing freezing point olute x1000 - point of Solvent of solution mass of urea (2) = loog Holar mass of urea (M)= 60 g/mol in moles of unea (m2) a wh 260.06 g/mee : molality of solution, (m)- ha a x1000 log = 0.1665 mole - 0.1665 mole 0.1665 mode 150 kq X1000 1.11 m kg/mol = kg of water = 1186 och - 1'86.c.kylmal = According to Roults law, STI= kgxm - 8Tf = 1.86 con x 1.12 mod 1 ATJ - 2.0646 °c we know freezing point of Dater = 0°C ng point of i freezing point of unea solution (T) Ty' - ATF 2 0°c - 2.0646 °C [-2.0646 °C freezing point of solution decreases.

6. Elevation of boiling point and Roulto land - When a non-volatile, non-electrolyte solute dissolved in a solution, the boiling point of the solution increases than pune solvent According to Roults Law, 4T6= Kom m= molality of solution Kb = Ebulioscopic constant Atb= change in temperature - To-To = Boiling point of solution - boiling point of pune solvent But, in case of electrolyte solute solution, Cionic compound) atb = i koxm iz vant Hotf factor is vonic solid It dissociates to form kt f cu ione molality of kel solution (M = 0.75m Ko for water a 0.51 om kel is vonic soli According ng to Roults » law, Sto=i koxm Atb = 1,85x0.51 oy x O. Ihm &Tb = 0.7076 a 1 point of pure water (To) = look Now, boiling in Boiling point of solution of kee (16) = OTO & To - (0.7076+ 100) oc - 100.7076 Boling point elevates.