C2 5 Acids And Alkalis Flashcards
What are bases?
Bases are substances that will neutralise acids.
What are acids?
Acids are substances which produce H+ ions when we add them to water.
What is an alkali?
An alkali is a soluble hydroxide. Alkalis produce OH- ions when we add them to water.
What does the pH scale show?
The pH scale shows how acidic or alkaline a solution is
Give three examples of alkaline products:
- Bleach
- Washing up liquid
- Soap
Give three examples of acidic substances:
- Hydrochloric acid
- Car battery
- Lemon juice
What happens when an acid reacts with an insoluble base?
A salt and water is formed, this is a neutralisation reaction.
What happens when an acid reacts with a metal?
When an acid reacts with a metal, a salt and hydrogen is formed.
How do you make a copper salt?
Add insoluble copper oxide to sulphuric acid and stir. Warm gently on a tripod and gauze.
The solution turns blue as the reaction occurs. This shows that copper sulphate has been formed, excess copper oxide can be seen.
When the reaction has completed, filter the solution to remove excess copper oxide.
We can then evaporate the water so that crystals of copper sulphate start to form. Stop heating when the first crystals appear and leave the rest of the water to evaporate slowly. This will make larger crystals.
How can we make an insoluble salt?
We can make an insoluble salt by reacting solutions of two soluble salts together.
What is another way of thinking about neutralisation?
H+ ions reacting with OH- ions to form water. (H2O).
Give some characteristics of ammonium nitrate
Contains a high proportion of nitrogen and is soluble in water. It’s ideal for a source of nitrogen for plants to take up through their roots.
Ammonium salts are formed by adding ammonia solution to an acid until there is a small excess of ammonia.
The ammonium salt is then crystallised from the solution and the excess ammonia evaporates off.
How to make insoluble salts
We add two solutions that contain different soluble salts. When the solutions react to form an insoluble salt, a precipitate is formed so this is a precipitation reaction.
PROCESS:
For example soluble salts:
We add potassium iodide solution to lead nitrate solution and stir. The precipitate of lead iodide that forms is filtered off from the solution. The precipitate is washed with distilled water and dried.
Using precipitation
- Precipitation reactions are used to remove pollutants from the waste water from factories.
- Precipitation can also be used to remove unwanted ions from drinking water.
