Salt preparation

Question 1

When should titration method be used?

Answer 1

When the salt is soluble and both starting reactants are soluble

Question 2

When should reaction with acid method be used?

Answer 2

When the salt is soluble and a starting reactant is insoluble

Question 3

When should precipitation method be used?

Answer 3

When the salt is insoluble

Question 4

What reaction(s) with acids cannot be used to create copper, silver and gold salts and why?

Answer 4

Acid with metal. They do not dissolve in acids.

Question 5

Why must titration be used instead of reaction with acid for some cases?

Answer 5

Since both starting reactants are soluble, there must be no excess when it is crystallised otherwise the crystals will contain some of the starting reactant.

Question 6

What are the steps to reaction with acid method?

Answer 6

1. Add an excess amount of the chosen reactant to a fixed volume of acid
2. Filter the excess reactant out
3. Heat the filtrate in an evaporating dish until it is saturated
4. Leave it to cool and crystallise on the evaporating dish
5. Filter to collect the crystals, wash and dry between sheets of filter paper

Question 7

What are the steps to titration method?

Answer 7

1. Conduct titration with a fixed volume of one reactant to find the exact amount of the other reactant needed
2. Mix the calculated volumes of reactants together
3. Heat the solution in an evaporating dish until it is saturated
4. Leave it to cool and crystallise on the evaporating dish
5. Filter to collect the crystals, wash and dry between sheets of filter paper

Question 8

Why can we not perform crystallisation using the solution directly from a titration?

Answer 8

The indicator is an extra chemical in the solution, which will slow down/prevent the crystallisation from taking place

Question 9

What are the steps to precipitation method?

Answer 9

1. Mix the starting reactants in a beaker and stir until no more precipitate forms
2. Filter to collect the precipitate as the residue
3. Wash the precipitate and dry between sheets of filter paper

Question 10

Why can an insoluble salt not be prepared using an insoluble starting reactant?

Answer 10

The salt will form a barrier around the starting reactant, preventing any furthur reaction between the starting reactant and the solution.