Ionic Equations and Precipitations

Question 1

Why can ionic structures conduct electricity in water?

Answer 1

The ionic lattice structure breaks up in water and the ions are free to move. In precipitation reactions the ions can move but they have to collide to react.

Question 2

Why does a precipitate seem instantaneous?

Answer 2

There is an extremely high collision frequency so the reaction happens very quickly.

Question 3

How can precipitation reactions be summarised?

Answer 3

AB + CD —> AD + CB

Question 4

How do we prepare a clean and dry sample of an insoluble salt?

Answer 4

• Mix barium chloride and sodium sulphate to form barium sulphate and sodium chloride
• Filter the precipitate of barium sulphate, which stays in the filter paper
• Wash with distilled water to remove any traces of sodium chloride
• Dry by leaving the precipitate in a warm, dry place to let the water evaporate

Question 5

What is a spectator ion?

Answer 5

Ions that don’t directly take part in the reaction, eg. when lead nitrate and sodium iodide react only the lead and iodide ions react and are precipitated out, making the nitrate and sodium ions the spectator ions.