Acids, Bases And Salts Flashcards
What colours do litmus solution go in acid, neutral and alkaline?
Acid: pale red
Neutral: purple
Alkaline: blue
What colours does red litmus paper go in acid, neutral and alkaline?
Acid: red
Neutral: stays red
Alkaline: blue
What colours does blue litmus paper go in acid, neutral and alkaline?
Acid: red
Neutral: stays blue
Alkaline: blue
What colours does phenolphthalein go in acid, neutral and alkaline?
Acid: colourless
Neutral: colourless
Alkaline: pink
What colours does methyl orange go in acid, neutral and alkaline?
Acid: red
Neutral: orange
Alkaline: yellow
What colours does universal indicator go in acid, neutral and alkaline?
Acid: red
Neutral: green
Alkaline: purple
What causes acidity?
The H+ ion
What does the pH scake measure?
Concentration of H+ ions
Is a logarithmic scale, like richter scale, so pH 1 contains 10x more H+ ions than pH 2, and 100x more than a pH of 3
What is a more accurate measure of finding out pH?
A pH meter
Define an arrhenius acid
An acid that dissolves into water to form hydrogen ions
What is the difference between calling an acid concentrated/dilute and calling an acid strong/weak
A concentrated acid is where there is lots of acid molecules dissolved into water
BUT
A strong acid is where lots of acid molecules have disassociated into H+ ions
What is it called when an acid dissolves into water and splits up into H+ and another ion?
Disassociation, or ionisation
What does the reversible arrow show?
Reaction does not go to completion, only some molecules ionise
Acids are weak if…..?
Few molecules ionise/dissociate
Define bases
A substance that can neutralise acids
Examples of bases?
Metal oxides and hydroxides
What are alkalis?
Bases that are soluble in water
(Ususally soluble metal hydroxides)
What is produced if a reactive metal and acid react?
Reactive metal + acid -> metal salt + hydrogen
What is produced if a base (alkali) reacts with an acid?
Base/alkali + acid -> metal salt + water
What happens if a metal carbonate reacts with an acid?
Metal carbonate + acid -> metal salt + water + carbon dioxide
What happens if ammonia reacts with an acid?
Ammonia + acid -> Ammonium salts
When making ionic equations, what is seperable, and what is inseparable?
Seperable
- acids
- ionic compounds
Inseperable
- elements
- covalent compounds
General form of an ionic equation of acid + hydroxide?
H+ + OH‐ -> H²O
General form of an ionic equation of acid + hydroxide?
H+ + OH‐ -> H²O
General form of an ionic equation of acid + ammonia?
H+ + NH³ -> NH⁴
How do you show something is hydrated?
With the • symbol, eg
CuSO⁴ • 5H²O
What is the test for water?
Anhydrous CuSO⁴ goes from white to blue
Or
Cobalt chloride paper goes from blue to pink
What type of scale is the pH scale?
Logarithmic
Symbol for phosphoric acid?
H³PO⁴
Symbol for ethanoic acid?
CH³COOH
Symbol for carbonic acid
H²CO³
What happens in a neutralisation reaction?
H+ ions from acid combine with OH- ions from alkali to form neutral H²O
When to use excess base method?
Base is soluble and salt produced is soluble
How to carry out excess base method?
- Combine base and acid, with excess amounts of base
- Once reaction complete, Filter out excess base
- Heat to evaporates off ~ ⅔ solution to make it saturated, making sure not to boil off all water as this will create anhydrous crystals
- Leave to cool and crystallise
What does anhydrous mean, and how can you convert hydrated crystals into anhydrous ones?
No water trapped in it.
Hydrated can be converted into anhydrous by heating to evaporates water out.
When to use titration?
Soluble base -> soluble salt
Procedure for titration?
- Use glass Pipette to measure exactly 25cm³ alkali into conical flask with a few Drops of indicator
- Put acid onto burette, and add to alkali slowly. Once it is nearly neutralised, add acid 1 drop at a time until indicator changes colour. Record volume of acid added from burette.
- Repeat whole Experiment again but without indicator
- Heat salt solution, evaporates some of the water away to make a saturated solution
- Leave to cool and crystallise
When to use precipitation method?
Soluble base -> insoluble salt
Procedure for precipitation method?
- Choose 2 suitable soluble solutions
(Generally metal nitrate and sodium compond) - Combine solutions and Filter the solution
- Wash precipitate with distilled water to remove impurities
- Leave to dry
What are the solubility rules for salts?
SOLUBLE
CANS ARE SOLUBLE
Chlorides ( except Ag and Pb)
All Na, K and NH⁴ salts
Nitrates
Sulphates ( except Ba, Pb and Ca )
INSOLUBLE
Carbonates ( except Na, K and NH⁴)
Hydroxides ( except Na, K and NH⁴)
How to choose which salt production method to use?
Insoluble salt: precipitation method
Soluble salt, but not Na, K or NH⁴ : excess base method
Soluble salt that is Na, K or NH⁴ : titration method
Which method does not require an acid?
Precipitation
