Reaction of oxides/ hydroxides with acid

Question 1

Na2O

Answer 1

• dissolves in acids
• exothermic reaction which produces a salt solution

Na2O (s) + 2H+ (aq) —> 2Na+ (aq) + 2OH- (aq)

Question 2

NaOH

Answer 2

• white pellet when solid (dissolves exothermically to give colourless solution)
• colourless solution when dissolved in water (becomes warmer)

NaOH (s) or (aq) + HCl (aq) —> NaCl (aq) + H2O (l)

Question 3

MgO

Answer 3

• dissolves in acids to form salt solution

MgO (s) + 2H+ (aq) —> Mg2+ (aq) + H2O (l)

Question 4

Mg(OH)2

Answer 4

• white solid/ ppt only sparingly soluble in water to give colourless solution
• solid/ ppt dissolves in acids to give colourless solution

Mg(OH)2 (s) + 2HCl (aq) —> MgCl2 (aq) + 2H2O (l)

Question 5

Al2O3

Answer 5

• dissolves in acids to form salt solution

Al2O3 (s) + 6H+ (aq) —> 2Al3+ (aq) + 3H2O (l)

Question 6

Al(OH)3

Answer 6

• white solid/ ppt insoluble in water
• dissolves readily in acids to form salt solution

Al(OH)3 (s) + 3HCl (aq) —> AlCl3 (aq) + 3H2O (l)