Other alkaline solutions
4 marks · NormalPotassium carbonate and ammonia both form alkaline solutions in water.
Write a balanced chemical equation to show how ammonia forms an alkaline solution when dissolved in water.
State the name and formula of the ion responsible for alkalinity in these solutions.
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(a) \ce{NH3(aq) + H2O(l) -> NH4^{+}(aq) + OH^{-}(aq)}
(b) hydroxide ion, OH^-
Common mistakes: NH_3(aq) dissociating directly to NH_4^+ and OH^-
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Marking points
M1 (a) · 1 mark · Writes correct reactants: NH_3 and H_2O.
A1 (a) · 1 mark · Gives balanced equation with products NH_4^+ and OH^-.
B1 (b) · 1 mark · States the correct name: hydroxide ion.
B1 (b) · 1 mark · Gives the correct formula: OH^-.
Worked solution
a)
b) The ion responsible for alkalinity is the hydroxide ion, formula OH^-.