Question

calculate the freezing point of a solution containing 50.0g of ethylene glycol (molecular weight =62) dissolved in 600g of water. (kf for water = 1. 86/mol).Give the uses of freon 12, DDT, carbon tetrachloride and iodoform. ​

Answer 1

Answer :

Mass of ethylene glycol = 50g

Mass of water = 600g = 0.6kg

Molar mass of ethylene glycol = 62g/mol

K(f) of water = 1.86 K kg/mol

We have to find freezing point of the solution $.$

★ Depression of freezing point :

• The lowering of vapour pressure of a solution causes a lowering of the freezing point compared to that of the pure solvent.
• The decrease in freezing point is known as depression in freezing point.

Formula : ∆T(f) = K(f) × m

where m denotes molality of solution

★ Molality is defined as number of moles of solute per 1 kg of the solvent.

• m = moles/mass of solvent
• m = (50/62)/0.6
• m = 1.34 moles/kg

➝ ∆T(f) = K(f) × m

➝ ∆T(f) = 1.86 × 1.34

➝ ∆T(f) = 2.49

Depression of FP :

➝ ∆T(f) = T°(f) - T(f)

➝ 2.49 = 0 - T(f)

➝ T(f) = -2.49 °C

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★ Uses of freon 12 :

• It is used as refrigerants, blowing agents, propellants in medical applications degreasing and solvent.

★ Uses of DDT :

• It is used as pepticides.

★ Uses of CCl₄ :

• It is used as a solvent for oils, fats, lacquers, varnishes, rubber waxes.

★ Uses of iodoform :

• It is used as am antiseptic in dressing of wounds.