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NEET-XII-Chemistry

02: Solutions

with Solutions - page 2
Qstn# A-11 Prvs-QstnNext-Qstn
  • #11
    Calculate
    the mass of ascorbic acid (Vitamin C, C6H8O6)
    to be dissolved in
    75 g of acetic acid to lower its melting point
    by 1.5°C. Kf = 3.9 K kg mol-1.
    Ans : Mass
    of acetic acid, w1 = 75 g
    Molar
    mass of ascorbic acid (C6H8O6), M2 = 6 × 12 + 8 × 1 + 6 × 16
    =
    176 g mol-1
    Lowering
    of melting point, ΔTf = 1.5 K
    We
    know that:


    = 5.08 g
    (approx)
    Hence,
    5.08 g of ascorbic acid is needed to be dissolved.
    Note: There is a slight variation in this answer and the one given in the
    NCERT textbook.