2b.3 - Acids, Alkalis and Bases Flashcards
What does the pH scale go up to?
pH 14
What makes an acid an acid?
H+ ions
What is a base?
A substance with a pH greater than 7
What is an alkali?
A base dissolved in water
What makes an alkali an alkali?
OH- ions
What is the word equation for neutralisation?
acid + base -> salt + water
What is the symbol equation for neutralisation in terms of H+ and OH- ions?
H+ + OH- -> H2O
Write the word equation for the reaction of acids and metals
acid + metal -> salt + hydrogen
What is the test for hydrogen?
Squeaky pop
Why do copper, silver, gold and platinum not react with dilute acid?
They are less reactive than hydrogen
What type of salts are produced when hydrochloric acids are reacted with metals?
Chloride salts
What type of salts are produced when sulfuric acids are reacted with metals?
Sulfate salts
What type of salts are produced when nitric acids are neutralised?
Nitrate salts
Give examples of bases
- Metal oxides
- Metal hydroxides
What is produced when you react hydrochloric acid with copper oxide?
Copper chloride and water
What is produced when you react hydrochloric acid with sodium hydroxide?
Sodium chloride and water
What is produced when you react sulfuric acid with zinc oxide?
Zinc sulfate and water
What is produced when you react sulfuric acid with calcium hydroxide?
Calcium sulfate and water
What is produced when you react nitric acid with magnesium oxide?
Magnesium nitrate and water
What is produced when you react nitric acid with potassium hydroxide?
Potassium nitrate and water
What is the chemical formula of ammonia?
NH3
What is the word equation for the neutralisation of ammonia?
ammonia + nitric acid -> ammonium nitrate
Why is the neutralisation of ammonia different from most other neutralisation reactions?
There is no water produced - just the ammonium salt
Why is ammonium nitrate a good fertiliser?
It has nitrogen from two sources, the ammonia and nitric acid and plants need nitrogen to make proteins
How do you make a soluble salt using a metal or an insoluble base? (5)
- Add the metal or insoluble base the acid
- The solid will dissolve in the acid as it reacts
- Excess solid will sink to the bottom of the flask
- Filter the excess metal
- Crystallise it
How do you make soluble salts using an alkali? (3)
- You need to know exactly the right amount of alkali to neutralise the acid - you use an indicator
- Then repeat using exactly the same volumes of acid and alkali so the salt isn’t contaminated with indicator
- Then crystallise as normal
How do you crystallise when making soluble salts? (the last step)
Evaporate some water then leave it to evaporate slowly. This is crystallisation.
What do you need to do if the salt you are trying to make is insoluble?
Use a precipitation reaction
How do you do a precipitation reaction? (2)
- Pick two solutions that contain the ions you need (e.g to make lead chloride you need a solution with lead ions and chloride ions. You can use lead nitrate (most nitrates are soluble) solution with sodium (all group one compounds are soluble) chloride solution
- Filter it, wash it and dry it
Other than making insoluble salts, what else are precipitation reactions used for?
Removing poisonous ions from drinking water and making water softer
