Acids, Bases and Salts Flashcards
What is the pH scale?
A measure of how acidic or alkaline a solution is.
If a solution has a pH less than 7, is it acidic or alkaline?
It is acidic. The closer the pH value is to 0, the more acidic it is.
If a solution has a pH more than 7, is it acidic or alkaline?
It is an alkali or a base. The closer to 14 the number, the more alkaline it is.
What is an alkali?
A soluble base
If a solution has a pH of 7, is it acidic or alkaline?
It is neutral.
What is an example of a neutral substance?
Pure water
How can one test for pH?
Using Universal Indicator.
What colour does Universal Indicator turn when it comes into contact with an acid?
Red
What colour does Universal Indicator turn when it comes into contact with a base?
Purple
What colour does Universal Indicator turn when it comes into contact with a neutral substance?
Green
What makes a dissolved substance acidic?
H+ ions
What makes a dissolved substance alkaline?
OH- ions
What is a neutralisation reaction?
A reaction between an acid and a base.
What is the general formula for a neutralisation reactions?
Acid + Base -> salt + water
Why is water produced during a naturalisation reaction?
The acidic H+ ions react with the negative OH- ions to make water.
What is the general equation for making salts from metals?
Acids + Metal -> Salt + Hydrogen
Why can’t highly reactive metals be used to make salts?
They react explosively when mixed with acids so aren’t safe.
Why can’t unreactive metals be hard to make salts?
The reaction would be too slow to make it worthwhile.
How can you see how reactive metals are?
By monitoring the rate of hydrogen production when a metal is mixed with an acid. The rate of hydrogen production is shown by the rate of bubbles produced.
How can one test for the presence of hydrogen gas?
You can put a lot splint into the test tube. If there’s a squeaky pop sound, hydrogen is present. The louder the pop, the more hydrogen there is.
How do you name a salt from a reaction with a metal?
The first half of the name is the metal. The second part of the name is the name of the non-acidic ion from the acid.
What salts does hydrochloric acid produce?
Chloride salt
What slats does sulphuric acid produce?
Sulphate salts
What is the general equation of making salts from metal (hydr)oxides?
Acid + Metal (Hydr)Oxide -> Salt + Water
How do you name the salt from a reaction with a metal (hydr)oxide?
The first half of the name is the metal name from the (hydr)oxide. The second half of the name is the name of the non-acidic ion from the acid.
How does one make a salt from ammonia?
You can react ammonia with nitric acid to make ammonium nitrate.
Ammonia + Nitric acid -> Ammonium nitrate
NH3(aq) + HNO3(aq) -> NH4NO3(aq)
What is a use of ammonium nitrate?
Fertiliser
How does one make a soluble salt from a metal or insoluble salt?
1) Put the acid in a beaker and mix with the insoluble reactant.
2) Keep adding the insoluble reactant until it is in excess.
3) User filter paper and a filter funnel to get the salt solution.
How do you make a soluble salt from an alkali?
You have to add expectations the right amount of alkali to neutralise the acid - Universal Indicator can be used to show when the reaction has finished. Then, take note of the quantities and repeat again without Universal Indicator so that the salt isn’t contaminated.
How does one get salt crystals from a salt solution?
1) Heat the solution to evaporate most of the water
2) Leave to cool at room temperature and the salt will crystallise
How does one make an insoluble salt?
Using a precipitation reaction. Just pick two aqueous solutions containing the required ions and mix them. You can then filter the salt out.
What are three other uses of precipitation reactions?
- To remove poisonous ions from drinking water
- Softening water
- Sewage treatment
