5 - Reactions with acids Flashcards
Why can’t we add copper to sulphuric acid?
Because copper is an unreactive metal so won’t react with the acid
Why can’t we add copper hydroxide to copper sulphate?
Because as it is an alkali it creates a solution. It will be difficult to get a neutral solution as we can’t easily see when all the acid has been neutralised
Why should we add copper carbonate to copper sulphate?
Because the green powder fizzes when added to acid and so we can easily see when the reaction is over and all the acid has been used up
Why do we have to evaporate the water to make salt crystals?
To ensure there is no acid left as this will contaminate the salt crystals
How do we know all the acid has reacted when making salt crystals?
-we need to add excess solid to the acid. This will ensure all the acid reacts and the excess solid can be removed easily by filtering
How do we get salt crystals from a solution?
-heat the solution gently or leave it by a window sill to evaporate slowly
Describe the preparation of copper sulphate crystals
-a beaker is used to put the sulphuric acid into and then a scoop of sulphate is added
-the solution will start to fizz as it is reacting
-more than one scoop of copper carbonate needs to be added as copper is unreactive
-this forms a blue copper sulphate solution and then a filter funnel is used to remove the excess copper carbonate by filtration, and the crystals are obtained by evaporation, by gently heating the solution or leaving it to evaporate at room temperature
Copper carbonate + sulphuric acid = copper sulphate
What is an acid?
A substance that contains hydrogen ions and they turn universal indicator red to yellow and neutralise bases
What are the acids used in the lab called?
Nitric acid
Hydrochloric acid
Sulphuric acid
What is a base?
Metal oxides
It is an alkali if soluble. They contain hydroxide ions and a base won’t affect universal indicator as it is not soluble, but an alkali will turn it purple. A base will neutralise an acid
What are salts?
Substances that are formed when an acid reacts with a base or an alkali
How do we know when an acid just neutralises an alkali?
- universal indicator (add acid until it turns green)
- add a phenolphthale indicator, pink in alkali and colourless in acid. The alkali has been neutralised when all the pink colour has disappeared
What is the risk assessment of hydrochloric acid?
Hazard: irritant
Risk: when pouring into a beaker could splash into eyes or skin
Wear goggles to minimise risk
Metal + acid and observation
Salt + hydrogen
Fizzes, temp rises, metal dissolved
Metal oxide + acid and observation
Salt + water
Temp rises, solid dissolves
