Salt Preparation Methods

Question 1

What colour will phenolphthalein turn in acid?

Answer 1

Colourless

Question 2

What colour will phenolphthalein turn in alkali?

Answer 2

Pink

Question 3

What colour will methyl orange turn in acid?

Answer 3

Red

Question 4

What colour will methyl orange turn in alkali?

Answer 4

Yellow

Question 5

What is the precipitation method and what does it prepare? [5]

Answer 5

Prepares insoluble salts
- Mix together the two solutions that each contain one of the two ions required for the salt. A precipitate is formed.
- Filter off the precipitate
- Wash by pouring a little distilled water over the precipitate in the filter paper
- Leave to dry

Question 6

What is the titration method and what does it prepare? [9]

Answer 6

Prepares soluble salts from an acid and a soluble base
- A known volume(25cm3) of acid is added to a conical flask
- Phenolphthalein is added
- The alkali is placed in a burette and slowly added to the conical flask
- When the indicator changes colour, showing neutralisation, the volume of alkali added is recorded
- The process is repeated to obtain an accurate, average value
- Once this exact volume is found, the process is repeated without the indicator to obtain a pure salt solution
- The salt solution is put in an evaporating basin and concentrated by removing 1/2 to 2/3rds of the solution
- Left to crystallise by forming large crystals

Question 7

What is the excess insoluble base method and what does it prepare? [7]

Answer 7

Prepares soluble salts from an insoluble base
- The appropriate acid is placed in a beaker and warmed with a bunsen burner over a tripod and gauze
- A small portion of the appropriate insoluble base is added to the warm acid and stirred
- Keep adding the base until all of the acid has reacted and some of the solid is left
- Filter off the solutin to remove the unreacted base
- Boil off 1/2 to 2/3rds of the filtrate in an evaporating basin to concentrate the solution
- Leave to crystallise

Question 8

Are nitrates soluble or insoluble?

Answer 8

All are soluble

Question 9

Are chlorides soluble or insoluble?

Answer 9

Soluble, except lead(III) and silver

Question 10

Are sulfates soluble or insoluble?

Answer 10

Soluble, except Calcium, Barium, and Lead(III)

Question 11

Are carbonates soluble or insoluble?

Answer 11

Insoluble, except for potassium, sodium, and ammonium

Question 12

Are hydroxides soluble or insoluble?

Answer 12

Insoluble, except for potassium, sodium, and ammonium

Question 13

True or false: All potassium, sodium, and ammonium salts are soluble.

Answer 13

True