write an activity to show one liquid diffuse into another liquid
Answers
Explanation:
Apparatus
Eye protection
Petri dish
Forceps
White tile or piece of white paper
Chemicals
Lead nitrate (TOXIC, DANGEROUS FOR THE ENVIRONMENT), 1 crystal
Potassium iodide, 1 crystal
Deionised water
Procedure
Place a Petri dish on a white tile or piece of white paper. Fill it nearly to the top with deionised water.
Using forceps, place a crystal of lead nitrate at one side of the petri dish and a crystal of potassium iodide at the other.
Observe as the crystals begin to dissolve and a new compound is formed between them.
SHOW FULLSCREEN
A diagram showing a petri dish, with crystals of potassium iodide and lead nitrate at opposite ends
Teaching notes
The lead nitrate and potassium iodide each dissolve and begin to diffuse through the water. When the lead ions and iodide ions meet they react to form solid yellow lead iodide which precipitates out of solution.
lead nitrate + potassium iodide → lead iodide + potassium nitrate
Pb(aq) + 2I–(aq) → PbI2(s)
The precipitate does not form exactly between the two crystals. This is because the lead ion is heavier and diffuses more slowly through the liquid than the iodide ion.