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Equilibrium · Question 41

AIPMT 2015 (Cancelled)MCQMedium📈 Topic in 38% papers+4−1
1

The Ksp of Ag2CrO4, AgCl, AgBr and AgI are respectively, 1.1 10-12, 1.8 10-10, 5.0 10-13, 8.3 10-17. Which one of the following salts will precipitate last if AgNO3 solution is added to the solution containing equal moles of NaCl, NaBr, NaI and Na2CrO4?

  1. AgBr
  2. Ag2CrO4
  3. AgI
  4. AgCl

Answer

(2) Ag2CrO4

Solution

A salt starts to precipitate when the ionic product just exceeds its Ksp. The salt that needs the largest [Ag+] precipitates last.

Let each anion have the same concentration, say 0.1 M.

AgI: [Ag+] = 8.3 10-170.1 = 8.3 10-16 M

AgBr: [Ag+] = 5.0 10-130.1 = 5.0 10-12 M

AgCl: [Ag+] = 1.8 10-100.1 = 1.8 10-9 M

Ag2CrO4: [Ag+]2[CrO42-] = Ksp

⇒ [Ag+] = 1.1 10-120.1 = 3.3 10-6 M

∴ Ag2CrO4 needs the highest [Ag+] and precipitates last.

Answer: (2)

AIPMT 2015 (Cancelled)

Keep practising — Equilibrium

2

If the value of equilibrium constant for a particular reaction is 1.6 1012, then at equilibrium the system will contain

  1. mostly products
  2. similar amounts of reactants and products
  3. all reactants
  4. mostly reactants.
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3

Which of the following salts will give highest pH in water?

  1. KCl
  2. NaCl
  3. Na2CO3
  4. CuSO4
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4

Using the Gibbs energy change, G = +63.3 kJ, for the following reaction, Ag2CO3(s) 2Ag+(aq) + CO32-(aq) the Ksp of Ag2CO3(s) in water at 25 C is ( R = 8.314 J K-1 mol-1)

  1. 3.2 10-26
  2. 8.0 10-12
  3. 2.9 10-3
  4. 7.9 10-2
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5

For the reversible reaction, N2(g) + 3H2(g) 2NH3(g) + heat The equilibrium shifts in forward direction

  1. by increasing the concentration of NH3(g)
  2. by decreasing the pressure
  3. by decreasing the concentrations of N2(g) and H2(g)
  4. by increasing pressure and decreasing temperature.
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6

For a given exothermic reaction, Kp and K'p are the equilibrium constants at temperatures T1 and T2, respectively. Assuming that heat of reaction is constant in temperature range between T1 and T2, it is readily observed that

  1. Kp > K'p
  2. Kp < K'p
  3. Kp = K'p
  4. Kp = 1K'p
AIPMT 2014
7

Which of these is least likely to act as a Lewis base ?

  1. BF3
  2. PF3
  3. CO
  4. F-
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8

Identify the correct order of solubility in aqueous medium.

  1. Na2S > CuS > ZnS
  2. Na2S > ZnS > CuS
  3. CuS > ZnS > Na2S
  4. ZnS > Na2S > CuS
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9

Accumulation of lactic acid (HC3H5O3), a monobasic acid in tissues leads to pain and a feeling of fatigue. In a 0.10 M aqueous solution, lactic acid is 3.7% dissociated. The value of dissociation constant, Ka, for this acid will be

  1. 1.4 10-5
  2. 1.4 10-4
  3. 3.7 10-4
  4. 2.8 10-4
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10

At 100 the Kw of water is 55 times its value at 25 . What will be the pH of neutral solution? (log 55 = 1.74)

  1. 7.00
  2. 7.87
  3. 5.13
  4. 6.13
NEET 2013 (Karnataka)
11

The values of Ksp of CaCO3 and CaC2O4 are 4.7 10-9 and 1.3 10-9 respectively at 25 . If the mixture of these two is washed with water, what is the concentration of Ca2+ ions in water ?

  1. 5.831 10-5 M
  2. 6.856 10-5 M
  3. 3.606 10-5 M
  4. 7.746 10-5 M
NEET 2013 (Karnataka)

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