Acids And Alkalis Flashcards
what happens when an acid reacts with a base
They neutralise each other: acid + base —> salt + water
What is the reactivity series
Please(potassium) Stop(sodium) lying(lithium), calling(calcium) me(magnesium) a(aluminium) careless(carbon) zebra(zinc) instead(iron) try(tin) learning(lead) how(hydrogen) copper saves(silver) gold platinum
What are the 3 main acids
- Hydrochloric: HCl
- Sulfuric acid: H2SO4
- Nitric acid: HNO3
Metal + acid —->
Metal + acid —> salt + hydrogen
Metal oxide + acid
Metal oxide + acid —> salt + water
Metal hydroxide + acid
Metal hydroxide + acid —> metal salt + water
Metal carbonate + acid
Metal carbonate + acid —> metal salt + carbon dioxide + water
Ammonia + acid
Ammonia + acid —> ammonium ions
What is the symbol for hydroxide
OH(-1 charge)
What is symbol for sulfate
SO4 (2- charge)
What is symbol for Carbonate
CO3(2- charge)
What is symbol for nitrate
NO3 (- charge)
How do you make a soluble salt
- pick an acid and an insoluble base
- gently warm dilute acid using Bunsen burner
- turn it off
- add insoluble base to acid, wait for it to react
- Now there should be some excess left over
- filter out the excess to get the salt solution
What pH does stomach acid typically have?
About 2
The pH of a solution can be measured using a type of chemical dye that changes colour, depending on the pH of the substance it’s mixed with.
This chemical dye is usually referred to as:
Universal indicator
Universal indicator is made up of….
- several different indicator solutions.
- This means that it undergoes a smooth colour change over a wide range of pH values.
- It becomes more red in colour in acidic solutions,
- but more bluey-purple in alkaline solutions.
pH of pure water
7
reasons why using a pH probe may be more reliable than using an indicator.
- A probe produces a more accurate result
- Determining the colour of an indicator is subjective
A substance that forms an aqueous solution with a pH less than 7 is…
An acid
What ion is responsible for making an alkaline pH when dissolved in solution
OH-
When acid molecules are added to water and split apart, we say that they…
Ionise
Do strong or weak acids completely ionise
- Strong acids ionise completely
- weak acids only partially ionise.
Is the dissociation or ionising of weak acids a reversible reaction
Yes - the products can react together to reform the acid.
For a weak acid, does the position of equilibrium lie to the left or the right?
Left
Carbonic acid is described as a weak acid, explain why
- It does not fully ionise to release hydrogen ions
- It will form a solution with a pH of less than 7
How do you describe the strength of acids
The proportion of acid molecules which dissociate into hydrogen ions
The concentration of an acid refers to…
the number of moles of acid molecules per unit of volume.
Is the strength of an acid is the same as its concentration.
No
- an acids strength refers to how well it ionises (dissociates) when added to water.
- its concentration refers to how many molecules there are per dm3 of solution.
As the concentration of hydrogen ions in a solution increases, what happens to the pH?
The pH decreases
What type of reaction is it when an acid and a base react together?
Neutralisation reaction
What happens during neutralisation
During a neutralisation reaction, the positive hydrogen ions from the acid react with the negative hydroxide ions from the alkali to form molecules of water.
How to obtain soluble salt crystals from an acid-base reaction
1) Place dilute acid in a beaker and heat gently.
2) Add the solid base bit by bit until it stops reacting, which means it’s in excess.
3) Isolate the salt solution by filtering out the excess solid base using filter paper and a funnel.
4) Heat the salt solution gently in a water bath until crystals start to form.
5) Let the solution cool further, which will cause more crystals to precipitate.
6) Filter out the soluble salt crystals using filter paper and funnel.
When a soluble salt is formed from an acid and an insoluble base, how do you know when an excess of base has been added?
Some of the reactant will be left unreacted
