4. Chemical changes (required practical 1 - making soluble salts) Flashcards
1
Q
What do all salts contain?
A
A positive ion
2
Q
What colour are copper sulfate crystals?
A
blue
3
Q
What are the steps for the practical?
A
- Start with a fixed volume of dilute sulfuric acid. This is our limiting reactant
- Gently heat the acid until almost boiling
- Use a spatula to add small amounts of copper oxide to the acid
- Stir the solution using a glass rod
- The copper oxide will react and seem to disappear, and the solution will turn a blue colour
- Continue adding the copper oxide if the solution continues to be clear blue
- Then stop adding copper oxide if some powder remains after stirring
- Use filtration to remove the unreacted copper oxide
- Place the solution in an evaporating basin, and heat gently over a beaker of boiling water, until half the solution remains
- Leave the solution for 24 hours in a cool place for crystals to form
- Scrape crystals onto a paper towel and gently pat them dry
4
Q
Why do we not want any acid remaining at the end?
A
As this would contaminate our salt
5
Q
Why do we not want to boil the acid?
A
As it could bubble over when we add our other reactant, which would be dangerous
6
Q
If some powder (copper oxide) remains after stirring, what does this mean?
A
that the reaction has stopped and that all of the acid has reacted
7
Q
If all the acid has reacted, what has the solution become?
A
neutral
8
Q
What can soluble salts be made from?
A
from acids by reacting them with solid insoluble substances, such as
metals, metal oxides, hydroxides or carbonates
9
Q
What can salt solutions be crystalised to produce?
A
solid salts
