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Calculate the mass of ascorbic acid to be dissolved in 75g of acetic acid to lower its melting point by 1.5°C - CBSE (Science) Class 12 - Chemistry

ConceptColligative Properties and Determination of Molar Mass - Introduction

Question

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.

Solution

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:

triangleT_f = (K_fxxw_2xx1000)/(M_2xxw_1)

=>w_2=(triangle_fxxM_2xxw_1)/(K_fxx1000)

= (1.5xx176xx75) /(3.9xx1000)

= 5.08 g (approx)

Hence, 5.08 g of ascorbic acid is needed to be dissolved.

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Solution Calculate the mass of ascorbic acid to be dissolved in 75g of acetic acid to lower its melting point by 1.5°C Concept: Colligative Properties and Determination of Molar Mass - Introduction.
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