20 % of acetic acid is dissociated when its 5 g is added to 500 mL of water. The depression in freezing point of such water is _ _ _ _ _ × 10 - 3 C ∘ . Atomic mass of C , H and O are 12 , 1 and 16 a.m.u. respectively. [Given : Molal depression constant and density of water are 1 . 86 K kg mol - 1 and 1 g cm - 3 respectively.

Question

20 % of acetic acid is dissociated when its 5 g is added to 500 mL of water. The depression in freezing point of such water is _ _ _ _ _ × 10 - 3 C ∘ . Atomic mass of C , H and O are 12 , 1 and 16 a.m.u. respectively. [Given : Molal depression constant and density of water are 1 . 86 K kg mol - 1 and 1 g cm - 3 respectively.,

MARKS App · Accepted Answer

Van't Hoff factor (i) for dissociation of acetic acid can be written as follows, i = 1 + ( n - 1 ) α n = Number of ions α = Degree of dissociation ( i = 1 + 0 . 2 ( 2 - 1 ) = 1 . 2 ΔT f = iK f m ΔT f = Depression in freezing point K f = Molar depression constant m = molality ΔT f = 1 . 2 × 1 . 86 × 5 × 1000 60 × 500 ΔT f = 0 . 372 Δ T f = 372 × 10 - 3

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