Classification of alkali.

Question

Below are two equations showing how two alkalis react with water.

1) NaOH (aq) H2O (l) ----> Na (aq) OH - (aq)

2) NH3 (aq) H2) (l) ----> NH4 (aq) OH- (aq)

a) Name Both alkalis

b) Which is classified as weak alkali and why?

c) Which is classified as strong alkali and why?

d) What is the likely pH of each alkali?

Answer 1

a) Name Both alkalis

#1 is sodium hydroxide

#2 is called either ammonia , or ammonium hydroxide

b) Which is classified as weak alkali and why?

#2 is classified as weak, because it only releases about 1% of its OH- ions , & as a weak base it has a Kb (Kb = 1.8e-5)

c) Which is classified as strong alkali and why?

NaOH is classified as a strong base, because it releases 100% of its OH- ions. Na+ compounds have a reputation of releasing all of their ion to the solution

d) What is the likely pH of each alkali?

0.1 Molar NaOHhas a pH = 13,

0.1 Molar NH4OH has a pH = 11 (100 times weaker than the NaOH)