Which of the following changes occur when potassium iodide reacts with lead acetate?

Golden Rain Procedure – Tips & Tricks

Lead nitrate and potassium iodide are both solid, soluble ionic compounds. We will combine them for some amazing results.

1. Dissolve each salt in 400ml of distilled water in separate beakers.
2. Combine the liquids in the Erlenmeyer flask so you have 800ml in total. If you wish to use a 500 ml flask instead, simply cut the amounts of compounds and water in half. You will see a yellow precipitate of lead iodide fall out of solution.

Mastering chemistry challenge: How would you calculate the amounts needed yourself? Leave your answer in the comments.

PbI2 will immediately precipitate out, as it is insoluble in cold water.

3. Heat the solution until all of the lead iodide dissolves, you may need to heat it above 80 degrees Celsius. Heating the solution causes the solubility to increase just enough to dissolve all of the lead iodide.

Lead iodide precipitate – how to best view it

4. Let it cool. This time, the PbI2 precipitates out in a much more beautiful fashion. This is best viewed in a dark with bright sunlight shining onto the flask, for example through a garage window in the late afternoon. If the lead iodide settles too quickly, stir it with a long stirring rod or start magnetic stirring to keep the particles suspended – giving the “golden rain” effect.

The Golden Rain reaction

Here is the equation for this double-replacement reaction. Lead ii nitrate reacts with potassium iodide forming lead (II) iodide and potassium nitrate.

Pb(NO3)2 + 2KI -> PbI2 + 2KNO3
Net ionic equation: Pb+2 + 2I– -> PbI2(s)

Interesting fact: Lead is in the +2 oxidation state in this reaction. Lead (IV) iodide does not exist, because lead (IV) can oxidize iodide to iodine.

Lead / iodine complexes

Don’t use too much iodide, or this reaction will occur, forming the soluble colorless tetraiodoplumbate(II) complex ion.

PbI2 + 2I– -> PbI4-2

Safety & Disposal

Lead nitrate is toxic, the lethal oral dose is approximately 8 grams for an 80kg human. Do not ingest any and avoid skin contact or breathing the dust.

The lead iodide should be filtered and stored in your compound collection. Lead salts should not be washed down the drain. The remaining lead in the solution can be precipitated out with sodium sulfide, as lead sulfide is extremely insoluble. PbS should be stored in a hazardous waste drawer until it can be disposed of properly. Sodium carbonate can be used if a sulfide compound is not available.

If you are doing a lab report, here is an example.

Lead Iodide / Golden Rain experiment video

Here’s the complete experiment video

We filmed this short clip on the golden rain reaction to show how beautiful the flakes of lead iodide look in the sun, when they precipitate in the cooled down solution. The video was taken in a dark garage, with sunlight coming through a window.

About Lead Iodide

Lead (II) iodide is a bright yellow solid, that is slightly soluble in hot water. It is stable in air. The formula for lead iodide is PbI2, and its molar mass is 461.01 grams/mole. The symbol for lead is Pb because its latin name is plumbum.

Lead iodide is quite a heavy molecule from a molar mass perspective, because both lead and iodine are heavier atoms. It has a hexagonal close-packed crystal structure, which is why it crystallizes in thin hexagonal-shaped plates. If you love math and crystals, read this.

Lead iodide is used in the manufacturing of solar cells, and also as a photon-detector for x-rays and gamma rays.

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If you enjoyed this article about lead iodide and the golden rain experiment, check out making tin crystals, and read about standard reduction potentials and how to name ionic compounds

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Updated May 09, 2018

By Claire Gillespie

When you mix two substances, sometimes a chemical reaction takes place that results in a change of color, state or temperature. Mixing solid lead nitrate and solid potassium iodide results in a change of state. A cloudy yellow precipitate – an insoluble solid that comes from a liquid solution – forms.

When you add lead nitrate to potassium iodide, their particles combine and create two new compounds, a yellow solid called lead iodide and a white solid called potassium nitrate. Yellow clouds indicate that the chemical change has taken place.

When you mix two chemicals, their particles may combine and make two new compounds. When you combine lead nitrate and potassium iodide solutions, a double-replacement reaction happens. The two compounds react, and the positive ions and negative ions of the two reactants switch places, creating two new compounds.

The lead nitrate solution contains particles (ions) of lead, and the potassium iodide solution contains particles of iodide. When the solutions mix, the lead particles and iodide particles combine and create two new compounds, a yellow solid called lead iodide and a white solid called potassium nitrate.

You can use solutions of lead nitrate and potassium iodide or mix them as dry powders to create the chemical reaction.

To use solutions, pour the same amount of each powder into a test tube and add water to encourage the movement of molecules and ions.

Pour the lead nitrate solution into the test tube with the potassium iodide solution to form lead iodide, which looks like yellow clouds. The clouds are made up of tiny solid particles suspended in the solution. Potassium nitrate forms too, but it is white and disguised by the yellow lead iodide.

If you heat the solution, the lead nitrate dissolves completely. When it cools, it slowly crystallizes, creating large crystals.

To mix the compounds dry, pour both powders into one test tube, cover the opening with a finger, and shake the test tube vigorously. Typically, only liquids and gases have chemical reactions because their molecules are looser and can move around freely and collide with one another. The molecules in solids are tightly packed together, so they don’t have the freedom to move around and collide.

The shaking movement in this experiment makes the surface of the crystals collide with one another, starting a chemical reaction that creates a yellow powder, which is a combination of lead iodide and potassium nitrate.