Acids, Bases, Salt, titration and reactivity series Flashcards
Colour change for Litmus
Acid: Red
Alkali: Blue
Colour change for phenolphthalein
Acid: Colourless
Alkali: Pink
Colour change for methly Orange
Acid: Red
Alkali: yellow
Why is Litmus not suitable for titration indication?
It doesn’t have a clear colour change and no clear end point
Colour change for universal indicator
Acid: Red/Brown
Neutral: Green
Alkali: Purple
What will form when water is added to acids?
Hydrogen ions (H+)
What will form when water is added to alkalis?
Negative hydroxide ions (OH-)
What is neutralisation reaction?
When acids and alkalis are mixed together producing salts.
Definition of Combination Reaction
When two elements combine to form a compound.
Definition of Combustion Reaction
a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat
Definition of Displacement Reaction
When a more reactive element displaces a less reactive element from a compound
Definition of Decomposition Reaction
When one reactant breaks down into two or more products
Difference between alkalis and bases
Bases are insoluble in water and Alkalis are soluble in water
Definition of Crystallisation
Process when crystal forms
Ionic equation for neutralisation:
H + OH —-> H2O
Definition of Precipitate
A solid that is formed by a chemical reaction involving liquids or gases
What is a reducing agent?
A substance that tends to lose electron or be oxidized
What is a oxidising agent?
A substance that tends to oxidize other substance.
What is a Redox reaction?
A reaction that involve the transfer of electrons from one species to another
Definition of reductions:
Loss of oxygen and gaining electron
Definition of oxidation:
A substance gains oxygen and loses electrons.
Acid + Metal —->
Salt + Hydrogen
Acid + Alkali —–>
Salt + Water
Acid + Base (metal oxide) –>
Salt + Water
Acid + Metal carbonate –>
Salt + Water + Carbon Dioxide
Acid + Ammonia –>
Ammonium ions
How to carry out titration to work out concentration of unknown?
- Measure 25cm^3 of alkali using a pipette into a conical flask.
- Add Phenolphthalein
- Add acid to the burette and note starting volume.
- Add acid slowly until indicator chages colour.
- Record final volume and work out difference
- Repeat to get concordant results.
Concordant definition
Results that differ by 0.2 cm^3 or less
Steps to make a soluble salt from an acid and an insoluble base
- Add powdered insoluble reactant to acid in a beaker, one spatula at a time, stirring to mix. Continue adding powder until it is in excess, so that all the acids has reacted.
- Filter the mixture in the beaker to remove the excess solid. The filtrate now contains only the salt and water.
- Heat the solution on a evapourating dish over the bunsen burner. Stop heating when small crystals start to form.
- Leave the solution cool at room temperature.
- Dry it with filter paper.
Equation for rusting
Iron + Oxygen + Water –> hydrated Iron(II) oxide
3 Types of rust prevention
Galvanising, Barrier Method, Sacrificial protection
How does galvanising protect iron from rusting
Coat iron with a layer of Zinc. Zinc is higher in reactivity series so reacts instead of the iron with oxygen.
How does Barrier Method prevent iron from rusting
Coat iron with paint/grease/oil to stop oxygen and water reaching iron
How does sacrificial protection prevent iron from rusting
Attach a block of more reactive metal to iron. The more reactive metal is oxidised instead of iron.
How does sacrificial protection prevent iron from rusting
Attach a block of more reactive metal to iron. The more reactive metal is oxidised instead of iron.
