Acids, Bases and Salt Preparations

Question 1

What is a salt

Answer 1

A salt is a metal compound formed when the H in the acid is replaced by a metal

Question 2

What is the formula for ethanoic acid

Answer 2

CH3COOH

Question 3

Which chlorides are insoluble

Answer 3

Silver chloride (AgCl)
Lead chloride (PbCl2)

Question 4

Which sulfates are insoluble

Answer 4

Calcium sulfate
Barium sulfate
Lead sulfate

Question 5

Which carbonates are insoluble

Answer 5

All of them, except sodium, potassium and ammonium

Question 6

What are the three methods of preparing salts

Answer 6

Precipitation
Excess solid and acid
Titration

Question 7

How do you determine which method to use when preparing a salt

Answer 7

If the salt is insoluble, then use precipitation
If the salt is soluble and has either sodium, potassium or ammonium ions then use titration
If the salt is soluble and does not have any sodium, potassium or ammonium ions, use the excess solid and acid method

Question 8

Describe the process of precipitation

Answer 8

Mix the two solutions (one containing the cation and the other the anion) together in a beaker and stir with a glass rod until a precipitate forms. Separate the precipitate by filtration and then wash it with some distilled water. Lastly, dry it between two pieces of filter paper or in an over

Question 9

What are the requirements for the excess solid and acid method

Answer 9

This method is used to prepare a soluble salt. One of the reactants MUST be insoluble. This means that it can be a metal (more reactive than hydrogen), a metal oxide, a metal hydroxide or a metal carbonate

Question 10

Describe the excess solid and acid method

Answer 10

Add the solid to the hot dilute acid and stir until you can see it at the bottom of the beaker. Then, filter the mixture to remove any excess solid left and transfer the filtrate to an evaporating dish. There, heat it gently up to the point of crystallization until a saturated solution forms. Then, allow the solution to cool until crystals form and separate them by filtration. Lastly, rinse them with cold, distilled water and dry them between two pieces of filter paper

Question 11

Describe the process of titration

Answer 11

For the experiment you will need an alkali and an acid ( e.g sodium hydroxide and hydrochloric acid). First, transfer 25cm of the acid into a conical flask using a pipette and add a few drops of phenolphthalein indicator. Then, fill the burette with the alkaline solution and slowly add it into the conical flask until the indicator changes color form colorless to pink. Record the volume of the solution added. Then, repeat the titration until two concordant titres are obtained and calculate the average titre using them. In a clean flask, add the average volume of the alkali found and 25cm of the acid without any indicator. Then, transfer the salt solution to an evaporating dish and heat it gently to evaporate the water up to the point of crystallization. Allow the saturated solution to cool and separate the crystals by filtration. Lastly, rinse them with a small amount of cold water and dry them between two pieces of filter paper