Sodium Hydroxide Tests for Cations

Question 1

Colour of precipitate for copper (II) ion (Cu²⁺) reaction with sodium hydroxide (NaSO₄)

Answer 1

Blue

Question 2

Colour of precipitate for iron (II) ion (Fe²⁺) reaction with sodium hydroxide (NaSO₄)

Answer 2

Green

Question 3

Colour of precipitate for iron (III) ion (Fe³⁺) reaction with sodium hydroxide (NaSO₄)

Answer 3

Reddish-brown

Question 4

Process to test for ammonium ions (NH₄⁺) using sodium hydroxide (NaSO₄)

Answer 4

1. Add sodium hydroxide to the substance in a test tube.
2. Heat gently over a Bunsen burner with damp red litmus paper over the test tube.
3. If ammonium is present, ammonia gas is given off and litmus paper turns blue.

Question 5

Ionic equation for reaction using ammonium and sodium hydroxide

Answer 5

NH₄⁺ + OH^- —> NH₃ + H₂O