Reactions of oxides with strong bases

Question 1

Al2O3

Answer 1

• dissolves in excess base to from salt solution with colourless aluminate complex ion

Al2O3 (s) + 2OH- (aq) + 3H2O (l) —> 2[Al(OH)4]- (aq)

Question 2

Al(OH)3

Answer 2

• dissolves in excess strong base to form colourless aluminate complex ion (present in salt solution)

Al(OH)3 (s) + NaOH (aq) —> Na[Al(OH)4] (aq)

Question 3

SiO2

Answer 3

• no reaction with hot aqueous base under lab conditions
• needs hot and concentrated strong bases
• solution of silicate salt is formed

SiO2 (s) + 2OH-(aq) —> SiO3 2- (aq) + H2O (l)

Question 4

P4O10

Answer 4

• dissolves in strong base to form salt solution
  With excess OH-
  P4O10 (s) + 12OH- (aq) —> 4Po4 3- (aq) + 6H2O (l)

Question 5

SO3

Answer 5

• reacts directly with bases to form salt solutions

SO3 (s) + 2OH- (aq) —> SO4 2- (aq) + H2O (l)