Chemistry - Preparation of Salts

Salt Rules

1. All compounds of group1 elements are soluble

2. All ammonium salts are soluble

3. All nitrates are soluble

4. All chlorides, bromides and iodides are soluble except those of silver and lead

5. All sulfates are soluble, except those of Ca, Ba and Pb

6. All carbonates are insoluble, except the carbonates of group 1 elements and NH4

7. All hydroxides are insoluble, except the carbonates of group 1 elements and NH4

Precipitation method

1. Dissolve the two solids separately in water

2. Mix the two solutions together and stir with a glass rod. One of the solutions should be in excess.

3. Filter the reaction mixture with a filter paper and filter funnel and obtain the residue (ppt).

4. Wash the precipitate with distilled water to remove soluble impurities.

5. Dry the solid by placing in a desiccator or air dry.

Acid with excess solid method

1. Warm the soluble aqueous reactant in a beaker over a Bunsen burner, and add the insoluble solid in to the beaker while stirring with a glass rod.

2. Add the solid until it is in excess. The excess solid will form a sediment at the bottom of the beaker, This means all the dilute acid is completely reacted.

3. Filter the unreacted solid out of the solution to obtain the filtrate.

4. Pour this solution in to an evaporating basin and heat it to remove some water.

5. Dip a glass rod in to the solution and see whether crystals appear in the glass rod (this means the solution has reached saturation point.)

6. Cool the saturated solution to obtain the crystals. Filter the crystals out of the solution.

7. Wash and dry the crystals blotting with filter paper / air dry.

Titration method

1. Fill the burette with the acid and adjust the liquid level to graduation mark 0.00cm³.

2. Measure 25cm³ of the base using a pipette and transfer it to a conical flask.

3. Add two drops of indicator (phenolphthalein) to the conical flask and record the colour (pink colour).

4. Place the flask on a white tile keep it under the burette and start adding the acid little at a time.

5. Add the acid dropwise into the conical flask closer to neutralization point while swirling the solution in flask.

6. Stop adding the acid when the indicator in the conical flask shows a colour change (turns colourless)

7. Record the volume of the acid needed to neutralize the base.

8. Repeat the titration without adding indicator - using the recorded volumes.

9. Pour the solution in to an evaporating basin and heat it to remove some water.

10. Dip a glass rod in to the solution and see whether crystals appear on the glass rod.

11. Cool the saturated solution to obtain the crystals. Filter the crystals out of the solution.

12. Wash and dry the crystals blotting with filter paper / air dry.