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Solutions · Question 31

AIPMT 2012 (Mains)MCQEasy📈 Topic in 0% papers+4−1
1

Vapour pressure of chloroform (CHCl3) and dichloromethane (CH2Cl2) at 25 are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of CHCl3 and 40 g of CH2Cl2 at the same temperature will be (Molecular mass of CHCl3 = 119.5 u and molecular mass of CH2Cl2 = 85 u)

  1. 173.9 mm Hg
  2. 615.0 mm Hg
  3. 90.6 mm Hg
  4. 285.5 mm Hg

Answer

(3) 90.6 mm Hg

Solution

Moles of CHCl3 = 25.5119.5 = 0.213 mol

Moles of CH2Cl2 = 4085 = 0.47 mol

Total moles = 0.213 + 0.47 = 0.683 mol

⇒ xCHCl3 = 0.2130.683 = 0.31 and xCH2Cl2 = 1 - 0.31 = 0.69

By Raoult's law (as per NCERT, Example 2.5):

ptotal = p CH2Cl2 + ( p CHCl3 - p CH2Cl2) xCHCl3

= 41.5 + (200 - 41.5) 0.31

= 41.5 + 49.1

= 90.6 mm Hg

Answer: (3)

AIPMT 2012 (Mains)

Keep practising — Solutions

2

pA and pB are the vapour pressures of pure liquid components, A and B, respectively of an ideal binary solution. If xA represents the mole fraction of component A, the total pressure of the solution will be

  1. pA + xA (pB - pA )
  2. pA + xA (pA - pB )
  3. pB + xA (pB - pA )
  4. pB + xA (pA - pB )
AIPMT 2012 (Prelims)
3

A 0.1 molal aqueous solution of a weak acid is 30% ionized. If Kf for water is 1.86 C/m, the freezing point of the solution will be

  1. -0.18 C
  2. -0.54 C
  3. -0.36 C
  4. -0.24 C
AIPMT 2011 (Mains)
4

200 mL of an aqueous solution of a protein contains its 1.26 g. The osmotic pressure of this solution at 300 K is found to be 2.57 10-3 bar. The molar mass of protein will be (R = 0.083 L bar mol-1 K-1)

  1. 51022 g mol-1
  2. 122044 g mol-1
  3. 31011 g mol-1
  4. 61038 g mol-1
AIPMT 2011 (Mains)
5

The freezing point depression constant for water is 1.86 C m-1. If 5.00 g Na2SO4 is dissolved in 45.0 g H2O, the freezing point is changed by -3.82 C. Calculate the van't Hoff factor for Na2SO4.

  1. 2.05
  2. 2.63
  3. 3.11
  4. 0.381
AIPMT 2011 (Prelims)
6

The van't Hoff factor i for a compound which undergoes dissociation in one solvent and association in other solvent is respectively

  1. less than one and greater than one
  2. less than one and less than one
  3. greater than one and less than one
  4. greater than one and greater than one
AIPMT 2011 (Prelims)
7

An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase?

  1. Addition of NaCl
  2. Addition of Na2SO4
  3. Addition of 1.00 molal KI
  4. Addition of water
AIPMT 2010 (Prelims)
8

A solution of sucrose (molar mass = 342 g mol-1) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be (Kf for water = 1.86 K kg mol-1)

  1. -0.372 C
  2. -0.520 C
  3. +0.372 C
  4. -0.570 C
AIPMT 2010 (Prelims)
9

A 0.0020 m aqueous solution of an ionic compound [Co(NH3)5(NO2)]Cl freezes at -0.00732 C. Number of moles of ions which 1 mol of ionic compound produces on being dissolved in water will be (Kf = 1.86 C/m)

  1. 3
  2. 4
  3. 1
  4. 2
AIPMT 2009
10

0.5 molal aqueous solution of a weak acid (HX) is 20% ionised. If Kf for water is 1.86 K kg mol-1, the lowering in freezing point of the solution is

  1. 0.56 K
  2. 1.12 K
  3. -0.56 K
  4. -1.12 K
AIPMT 2007
11

During osmosis, flow of water through a semipermeable membrane is

  1. from solution having lower concentration only
  2. from solution having higher concentration only
  3. from both sides of semipermeable membrane with equal flow rates
  4. from both sides of semipermeable membrane with unequal flow rates.
AIPMT 2006

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