Question

36.

What is the net ionic equation for the acid–base reaction of hydrobromic acid with sodium hydroxide?

A)

NaOH(aq) + HBr(aq) → H2O(l) + NaBr(aq)

B)

Na+(aq) + –OH(aq) + H+(aq) + Br–(aq) → H2O(l) + Na+(aq) + Br–(aq)

C)

Na+(aq) + –OH(aq) + H+(aq) + Br–(aq) → H+(aq) + –OH(aq) + Na+(aq) + Br–(aq)

D)

–OH(aq) + H+(aq) → H2O(l)

Which salt forms a basic solution when dissolved in water?

A) KCl B) NH4Br C) LiNO3 D) Na3PO4

44.

A solution containing a low concentration HCl is a weak acid.

A) True B) False

Answer 1

1st question : B

Net ionic equation for the acid–base reaction of hydrobromic acid with sodium hydroxide

NaOH is strong base, so it will be completely dissociated in the solution.

                                             NaOH <==> Na⁺ + OH^-

HBr is a strong base, it will be completely dissociated in the solution:

                                             HBr <==> H⁺ +   Br^-

The ions will react to form H₂O and salt. NaBr is an electrolyte, so it will be completely dissociated into ions. So the net reaction will be:

                              B) Na⁺_(aq) + OH^-_(aq) + H⁺_(aq) + Br^–_(aq) → H₂O_(l) + Na⁺_(aq) + Br^–_(aq)

2nd Question: d

a.   KCl is a salt of strong base KOH and strong acid HCl. Thus in sloution after hydrolysis of KCl,   KOH and HCl will be formed . The strong base and strong acid will neutralize each other, making the pH of the solution 7.

b. NH₄Br is a salt of weak acid NH₄OH and strong acid HBr.

NH₄Br + H₂O = NH₄OH + HBr = NH₄OH + H⁺ + Br^-

HBr will be completely dissociated as it is a strong acd. Thus solution of NH₄Br will be acidic

c. LiNO₃ + H₂O = LiOH + HNO₃ = Li⁺ + NO₃^- + H₂O

LiOH is a strong base and HNO₃ is a strong acid. Thus solution will be neutral.

d. Na₃PO₄ + 3H₂O = H₃PO₄ + 3NaOH = H₃PO₄ + 3Na⁺   + 3OH^-

H₃PO₄ is weak base. NaOH will be completely dissociated in the solution making the solution basic.

3rd question : False

A weak acid is an acid that dissociates incompletely, releasing only some of its hydrogen atoms into the solution.

Thus dilution solution of a strong acid does not mean it is a weak acid. Whatever the concentration is, solution of HCl is always a strong acid as it is dissociated completely in the solution.