The low solubility of LiF and that of CsI in water are respective

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131.

The low solubility of LiF and that of CsI in water are respectively due to which of the following properties of the alkali metal ions?

  • Higher hydration enthalpy of Li, higher lattice enthalpy of Cs+

  • Smaller hydration enthalpy of Li, higher lattice enthalpy of Cs+

  • Smaller lattice enthalpy of Li, higher hydration enthalpy of Cs+

  • Higher lattice enthalpy of Li, smaller hydration enthalpy of Cs+


D.

Higher lattice enthalpy of Li, smaller hydration enthalpy of Cs+

If hydration energy is greater as compare to lattice energy then the salt is soluble, and if hydration energy is lesser as compared to lattice energy, then the salt is insoluble. 

LiF is almost insoluble due to high lattice energy. Both ions in LiF are very small. In this case, hydration energy is very less. 

In case of CsI both ions are larger in size. As a result both the ions in CsI are less hydrated therefore, its hydration energy will decrease. Hence, it is insoluble in water.


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132.

The relative strength of trichlorides of boron group to accept a pair of electron is given by

  • GaCl3 > AlCl3 > BCl3

  • AlCl3 > BCl3 > GaCl3

  • AlCl3 > GaCl3 > BCl3

  • BCl3 > AlCl3 > GaCl3


133.

If the ionic product of M (OH)2 is 5 × 10-10, then the molar solubility of M(OH)2 in 0.1 M NaOH is

  • 5 × 10-12 M

  • 5 × 10-8 M

  • 5 × 10-10 M

  • 5 × 10-9 M


134.

Equilibrium constants are given for the following two equilibria.

(i) A2 (g) + B2 (g)  2AB (g); K = 2 × 10-4 L mol-1

(ii) 2AB (g) + C2 (g)  2ABC (g); K = 2 × 10-2 L mol-1

Calculate the equilibrium constant for the following equilibrium.

ABC (g)  12A2 (g) + 12B2 (g) + 12C2 (g)

  • 500 mol1/2 L-1/2

  • 500 mol1/2 L1/2

  • 4 × 10-6 mol1/2 L1/2

  • 200 mol1/2 L-1/2


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135.

The equilibrium constant for the equilibrium PCl5 (g) PCl3 (g) + Cl2 (g) at a particular temperature is 2 × 10-2 mol L-1. The number of moles of PCl5 that must be taken in a one litre flask at the same temperature to obtain a concentration of 0.20 mole of chlorine at equilibrium is

  • 2.2

  • 2.0

  • 1.8

  • 0.2


136.

The correct increasing order of the acid strength of benzoic acid (I), 4-nitrobenzoic acid (II), 3,4-dinitrobenzoic acid (III) and 4-methoxybenzoic acid (IV) is

  • I < II < III < IV

  • II < I < IV < III

  • IV < I < II < III

  • IV < II < I < III


137.

Choose the correct order of decreasing basic strength of the following compounds in aqueous solution

(i) C6H5NH2

(ii) C2H5NH2

(iii) NH3

(iv) (CH3)2NH

  • (i) > (ii) > (iii) > (iv)

  • (iv) > (ii) > (iii) > (i)

  • (ii) > (i) > (iii) > (iv)

  • (iv) > (iii) > (ii) > (i)


138.

The salt of an alkali metal gives violet colour in the flame test. Its aqueous solution gives a white precipitate with barium chloride in hydrochloric acid medium. The salt is

  • K2SO4

  • KCl

  • Na2SO4

  • K2CO3


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139.

The values of limiting ionic conductance of H+ and HCOO- ions are respectively 347 and 53S cm2 mol-1, the dissociation constant of methanoic acid at 298 K is

  • 2.5 × 10-4

  • 2 × 10-5

  • 2.5 × 10-5

  • 1.5 × 10-4


140.

In a closed cylinder of capacity 24.6 L, the following reaction occurs at 27°C.

A2 (s)  B2 (s) + 2C (g)

At equilibrium, 1 gm of B2 (s) (molar mass = 50 g mol-1) is present. The equilibrium constant Kp for the equilibrium in atm2 unit is 

(R = 0.082 L atm K-1 mol-1)

  • 1.6 × 10-2

  • 1.6 × 10-5

  • 1.6 × 10-3

  • 1.6 × 10-4


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