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Silver halide precipitate equations

Mixing and soluble silver salt and any soluble halide (chloride, bromide or iodide) will produce a silver halide precipitate. The only commonly used soluble silver salt used in the "A" level laboratory is silver nitrate solution. The most commonly used soluble halides are the sodium and potassium salts. There are plenty of others that would work equally well - you can check this in the solubility table. It is important to get the ionic formulae right. If you think you may have forgotten these then check this link.

The following are the full equations for the reactions of silver nitrate solution with a potassium halide solution. It is important to include the correct state symbols:

In order to write an ionic equation we need to locate the spectator ions. We can start by taking the first equation and showing the individual ions present in any ionic solutions. Don't try to split up the ions in any solid - these are stuck together, but in solution the ions are separate and freely moving:

You should see that K⁺(aq) and NO₃^-(aq) are common to both sides. They have simply sat there and done nothing - these are the spectator ions and need to be left out:

This is a better equation as it shows more clearly what went on during the reaction. In fact, all that happened was that the silver ions and chloride ions came together to form a precipitate.

You may be given other equations to work out for these precipitate formations. The ionic equations are always the same, but the full equation could require some balancing. For example, the reaction between calcium chloride solution and silver nitrate solution. As stated above, it is important to use the correct ionic formulae: