Solutions Lecture-3
Osmotic pressure example
Solutions Lecture-3
Osmotic pressure example
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0.1M=Vn2
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C=Vn2=0.021.26/W2
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V=0.2L
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m2=1.26g
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T=300k
Solutions Lecture-3
Osmotic pressure example
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π=2.57×10−3bar
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π=CRT=W2×0.21.26×0.083×300
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W2=0.2×2.57×10−31.26×0.083×300
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W2=61.022g/mol
Solutions Lecture-3
Osmotic pressure example
Solutions Lecture-3
Osmotic pressure example
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4.98=L36/180RT
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C6H12O6 (72+12+96)
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π=1.52bar
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1.52=CRT
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C=0.083×300K1.52
Solutions Lecture-3
Abnormal molar masses
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As we know,
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ΔTb=Kbm
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NaCl→Naaq++Claq−
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0.1m0.1m0.1m
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0.05m0.050.05
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0.1(1−α)0.1α0.1α
Solutions Lecture-3
Abnormal molar masses
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2A→A2
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n(1−α)2nα
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Suppose we have AmBn
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c(1−α)
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Then conc. of A+ is c∝m & conc. of B− is c∝n
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c∝m c∝n
Solutions Lecture-3
Abnormal molar mass example
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Given
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M2=2g, M1=25g
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Molar mass of C6H5COOH =84+6+32=122 g/mol
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As C6H5COOH→(C6H5COOH)2
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12222α 1222(1−α)
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m=4.9×0.66(1−2α)
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Kf=4.9KKgmol−1
Solutions Lecture-3
Abnormal molar mass example
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As
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1−2α=0.500
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2α=0.500
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m=251222(1−α+2α)×1000
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m=0.66(1−2α)
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α=1
Solutions Lecture-3
Van’t hoff factor
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i=CthCexp=πthπexp
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i=ΔTthΔTexp
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=CalculatedexpColligativeProperties
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π=CRT
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ΔT=Kbm
Solutions Lecture-3
Van’t hoff factor example
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Volume of acetic acid 0.6 ml
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ρ=1.06g/ml
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V1=1L=1Kg of water ( as density is 1g/ml)
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ΔTf=0.0205∘C=Kfm
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i=?
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CH3COOH⇆CH3COO−+H+
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C(1−α)CαCα
Solutions Lecture-3
Van’t hoff factor example
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Kb=[CH3COOH][H+][CH3COO−]
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Kb=C(1−α)(Cα)2
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Kb=1−αCα2
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[C]=1kg0.6×1.06/60
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[C]=600.6×1.06m[M]
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[C]=1.06×10−2
Solutions Lecture-3
Van’t hoff factor example
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W2=10g
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W1=250g
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CH3CH2CHClCOOH
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ΔTf=Kfm=1.86×0.326
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HA→H++A
Solutions Lecture-3
Van’t hoff factor example
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C(1−α)Cα
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=0.645∘C
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Ka=1.4×10−3
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=[HA][H+A−]
Solutions Lecture-3
Van’t hoff factor example
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Kf=1.86KKg/mol
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m=C(1+α)
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=1−αCα2
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=1−α0.326α2
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α=0.0655
Solutions Lecture-3
Van’t hoff factor example
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C=weightofsolvent(Kg)molesofsolute
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Ka=0.93460.326α2
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α=0.0633
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i=1+α=1.0633
Solutions Lecture-3
Van’t hoff factor example
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W2=19.5g
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W1=500g
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CH2FCOOH
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HA→H++A−
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C(1−α)CαCα
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C(1+α)
Solutions Lecture-3
Van’t hoff factor example
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ΔTf=1.0∘C=Kfm=KfC(1+α)
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=1.86×0.5(1+α)
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i=CC(1+α)=(1+α)
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1+α=1.86×0.51.0=1.075
Solutions Lecture-3
Van’t hoff factor example
Solutions Lecture-3
Van’t hoff factor example
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Ka=C(1−α)(Cα)2
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=1−αCα2
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=0.9250.5×0.0752
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=3.0×10−3