481.

Which of the following pairs consitutes a buffer?

• HNO₂ and NaNO₂

• NaOH and NaCl

• HNO₃ and NH₄NO₃

• HNO₃ and NH₄NO₃

The hydrogen ion concentration of a 10^-8 M HCL aqueous solution at 298 K (K_w = 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

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

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

• HgI₂ , I₃^-

• Hgl₂, I^-

• HgI₄^3-, I₃^-

• HgI₄^3-, I₃^-

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

The most stable carbonium ion among the following is

• ${\mathrm{C}}_6{\mathrm{H}}_5 -{\mathrm{CH}}_2\stackrel{+}{\mathrm{C}}{\mathrm{H}}_2$

• ${\mathrm{CH}}_3\stackrel{+}{{\mathrm{CH}}_2}$

• ${\mathrm{C}}_6{\mathrm{H}}_5 -\stackrel{+}{\mathrm{C}}-{\mathrm{C}}_6{\mathrm{H}}_5$

• ${\mathrm{C}}_6{\mathrm{H}}_5\stackrel{+}{\mathrm{C}}{\mathrm{H}}_2$

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

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

100 mL of a solution contains 2 g of acetic acid and 3g of sodium acetate providing K_a =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

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

Mg_(s) + Cu²⁺ $\rightleftharpoons$ Mg²⁺ + Cu_(s); K₁ = 6 x 10⁹⁰

Fe_(s) + Cu²⁺ $\rightleftharpoons$ 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