Chemistry acids and bases Flashcards
Definition of an acid
And acid is a proton donor
Acid must have a hydrogen to donate (give away) an H+ ion (proton)
Acid dissociate (split up) into H+ ions and negative ions (anion) when added to water.
Definition of a bass/alkali
A base is a proton acceptor
Basis must be able to accept (gain) an H+ ion
The H+ ion is donated to base from acid
An alkali is a soluble base
Bases dissociate into OH- ions and positive metal ions when added to water
Common bases are:
MgO and NaOH
Neutralisation reactions
Neutralisation reactions occur when acids react with alkali. When these substances react, the H+ ions react with the OH- ions to produce water.
e.g hydrochloric acid
neutralises sodium hydroxide to form sodium chloride and water:
Net ionic equation for ALL acid base neutralisation reactions is:
H+ + OH- ➡️ H2O
Strong acids
The strength of an acid is not related to its concentration. A strong acid FULLY DISSOCIATES ism
water into H+ ions ALL H+ ions are donated and seperate from the anions
HCl(aq) ➡️ H+(aq) + Cl-(aq)
Weak acid
A weak acid only PARTIALLY DISSOCIATES in water into H+ ions SOME H+ are donated and the system forms an EQUILIBRIUM
CH3COOH(aq) ↔️ H+(aq) + CH3COO-(aq)
Strong acids have more H+ ions in solution that weak acids.
Amphiprotic v amphoteric
Some species are able to donate and accept protons water is an example as it can be accept a proton to become H3O+ or donate a proton to become OH-. These species are Amphiprotic.
Some species are able to react like an acid and a base
Aluminium hydroxide (Al(OH)3) is an example
These species are amphoteric.
Types of oxides
Most non-metal oxides are acidic E.G SO2, SO3, CO2
most metal oxide are basic E.G CaCO3, Na2O
Some metal oxide are amphoteric and reacts as both acid and base e.g Aluminium oxide -Al2O3 ZnO - zinc oxide
Testing oxides
Acidic and amphoteric oxides will react with metal carbonates (base) to form CO2 gas
Acidic oxides dissolve in water and lower the pH (universal indicator)
Basic and amphoteric oxides will react with acids and be neutralised
Thermal decomposition
Calcium oxide, CaO is manufactured from limestone by thermal decomposition
Limestone is a sediment rock comprised mainly of calcium carbonate, CaCO3
Thermal decomposition is a chemical reaction that involves breaking a substance apart using heat.
Acid
Turn blue litmus paper red
Methyl orange turns red-orange
Thymolpthalein turn colourless
pH under 7
Bases
Turn red litmus blue
Methyl orange turns yellow
Thymolphthalein turns blue
pH more than 7
Neutral
Does not change litmus
Methyl orange turns yellow
Thymolphthalein turn colourless
Ph 7
What is limewater
Lime water is the common name for a saturated aqueous solution of calcium hydroxide. Calcium hydroxide - Ca(OH)2, is sparingly soluble in water.
Displacement reaction
In a displacement reaction, the metal in the compound is replaced by the more reactive metal to form a new compound
Magnesium + copper sulfate ➡️ Mg + CuSO4
Copper + magnesium sulfate ➡️ Cu + MgSO4
