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.
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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.
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