Making insoluble salts
An Unable to dissolve in a particular solvent. For example, sand is insoluble in water. The substance formed when the hydrogen ion in an acid is replaced by a metal ion. can be prepared by reacting two suitable Mixture formed by a solute and a solvent. together to form a A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance, eg in a precipitation reaction..
Determining suitable solutions
All nitrates and all sodium salts are Able to dissolve in solvent. For example, sugar is soluble in water because it dissolves to form sugar solution.. This means a given precipitate XY can be produced by mixing together solutions of:
- X nitrate
- sodium Y
For example, to prepare a precipitate of calcium carbonate:
- X = calcium and Y = carbonate
- mix calcium nitrate solution and sodium carbonate solution together
calcium nitrate + sodium carbonate 鈫 sodium nitrate + calcium carbonate
Ca(NO3)2(aq) + Na2CO3(aq) 鈫 2NaNO3(aq) + CaCO3(s)
It also works if potassium carbonate solution or ammonium carbonate solution is used instead of sodium carbonate solution. Remember that all common potassium and ammonium salts are soluble.
Question
Name two suitable solutions that, when mixed together, will produce a precipitate of silver chloride.
Silver nitrate solution and sodium chloride solution (or potassium chloride solution, or ammonium chloride solution).
An outline method
This is an outline method for making a pure, dry sample of an insoluble salt.
- Mix together two suitable solutions (see above).
- Use Method used to separate an insoluble solid from a liquid using a physical barrier such as paper. to separate the precipitate as a The material left over at the end of a process, often the material that is removed during purification of a substance. from the solution.
- Wash the A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance, eg in a precipitation reaction. th distilled water while it is in the filter funnel.
- Leave the washed precipitate aside or in a warm oven to dry.
Reasons for each step
- Filtration separates insoluble substances from liquids and solutions.
- The precipitate is insoluble in water, so any remaining contaminating solution can be removed by washing it with distilled water.
Image caption, 1. One beaker contains a mixture of solid and liquid, the other contains a funnel with filter paper
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