Which of the following pairs consitutes a buffer? from Chemistr

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481.

Which of the following pairs consitutes a buffer?

  • HNO2 and NaNO2

  • NaOH and NaCl

  • HNO3 and NH4NO3

  • HNO3 and NH4NO3


A.

HNO2 and NaNO2

A pair constituent with an HNO2 and NaNO2 because HNO2 is weak acid and NaNO2 is a salt of the weak acid (HNO2) with a strong base (NaOH). Hence, it is an example of acidic buffer solution.

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482.

The hydrogen ion concentration of a 10-8 M HCL aqueous solution at 298 K (Kw = 10-14) is:

  • 1.0 x 10-6

  • 1.0525 x 10-7 M

  • 9.525 x 10-8 M

  • 9.525 x 10-8 M

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483.

Which of the following, not a correct statement? 

  • The electron -deficient molecules can act as Lewis acids

  • The canonical structures have no real existence

  • Every AB5 molecules does, in fact, have square pyramid structure

  • Every AB5 molecules does, in fact, have square pyramid structure

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484.

HgCl2 and I2 both when dissolved in water containing I ions the pair of species formed is

  • HgI2 , I3-

  • Hgl2, I-

  • HgI43-, I3-

  • HgI43-, I3-

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485.

When 750 mL of 0.5 M HCl is mixed with 250 mL of 2 M NaOH solution, the value of pH will be

  • pH = 7

  • pH > 7

  • pH < 7

  • pH = 0


486.

The most stable carbonium ion among the following is

  • C6H5 -CH2C+H2

  • CH3CH2+

  • C6H5 -C+-C6H5

  • C6H5C+H2


487.

Aqueous solution of AlCl3 is acidic towards litmus while of NaCl is not. The correct reason behind this is

  • AlCl3, furnishes OH- ion in the solution

  • AlCl3, furnishes H+ ion in the solution

  • AlCl3, furnishes both H+ well as OH- ion in the solution

  • AlCl3, is the salt of strong base and strong acid


488.

The melting point of solid substances is directly proportional to pressure acting on them. However, ice-melts at a temperature lower than its usual melting point, when the pressure increases. This is because

  • ice is not a true solid

  • the bonds break under pressure

  • ice is less denser than water

  • pressure generates heat


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489.

100 mL of a solution contains 2 g of acetic acid and 3g of sodium acetate providing Ka =1.8 x 10-5 , then choose the correct option.

  • This solution is basic in nature

  • This solution is acidic in nature

  • This solution is amphoteric in nature

  • This solution is neutral in nature


490.

Both Mg and Fe metal can reduce copper from a solution having Cu2+ ion, according to equilibria.

Mg(s) + Cu2+  Mg2+ + Cu(s); K1 = 6 x 1090

Fe(s) + Cu2+  Fe2+ + Cu(s); K2 = 3 x 1026

Choose the correct option regarding above equilibrium

  • Mg removes more Cu2+ from solution

  • Fe removes more Cu2+ from solution

  • Both will equally remove Cu2+ from solution

  • Both metals cannot remove Cu2+ from solution


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