Vapour pressure of pure water at 298 K is 23.8 mm. 50 g of urea (NH₂CONH₂) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Solution

Vapoure pressure of pure water (solvent) at 298 K, p⁰ = 23.8 mm
Vapour pressure of solution, p = ?
Mass of solvent ,W = 850 g
Mass of solute,M = 50 g
Mol. mass of water (H₂O), M = 18 g mol^–1Mol.mass of urea NH₂ CO NH₂= 14 + 2 + 12 + 16 + 14 + 2
= 60 g mol^–1According to Raoult's law, $\frac{p^{0} - p}{p^{0}} = \frac{ωM}{Wm}$

$p = p^{0} - \frac{w \times M}{m \times W} \times p °$

$p = 23.8 - \frac{50 \times 18}{60 \times 850}$

$= 23.8 - 0.017 = 23.78$
Hence, 23.78 mm Hg. Ans.

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Solutions

Vapour pressure of pure water at 298 K is 23.8 mm. 50 g of urea (NH₂CONH₂) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Some More Questions From Solutions Chapter

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

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Solutions

Vapour pressure of pure water at 298 K is 23.8 mm. 50 g of urea (NH2CONH2) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Some More Questions From Solutions Chapter

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 370C.

Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Vapour pressure of pure water at 298 K is 23.8 mm. 50 g of urea (NH₂CONH₂) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.