Acids + Alkalis/bases Flashcards
What is an acid
Any substance that forms an aqueous solution with a pH less than 7
They release H+ ions in solution (hydrogen ions)
What is a base
Any substance with a pH greater than 7
What is an alkali
A base that dissolves in water to form a solution with a pH greater than 7
Alkalis release OH- ions (hydroxide ions)
Strong acids
Strong acids ionise completely in water. This means they break up completely into H+ and other substance- ions
Straight one direction arrow means strong acid
Weak acids
Weak acids partially ionise in water. They do not fully release all H+ ions
Reversible reaction sign means weak acid
Weak/strong vs concentrated/dilute
Weak/strong measure the ionisation
Concentrated/dilute measures amount of stuff in volume
pH probe vs universal indicator
pH probe more accurate and precise as removes chance of human error
Neutralisation reactions
Acid + Base/alkali = salt + water
For example
HCl + NaOH = NaCl + H20
Common acids
Hydrochloric acid HCl usually 2HCL though
Sulphuric acid H2SO4
Nitric acid HNO3
Common bases
Sodium hydroxide NaOH
Calcium carbonate CaCO3
Hydrochloric acids makes substances ending in
Chloride
Sulphuric acid makes substances ending in
Sulfate
Reactions of metals + acids
More reactive metals than hydrogen can displace hydrogen from acids
Acid + metal = salt + hydrogen
Iron
Hydrochloric acid + iron = iron chloride + hydrogen
Sulphuric acid + iron = iron sulphate + hydrogen
Iron reacts fairly slowly with acids
This is because it’s less easy for iron to form Fe2+ ions
Fe = Fe2+ + 2e- is oxidation
2H+ +2e- = H2 is reduction
Magnesium
Hydrochloric acid + magnesium = Magnesium chloride + hydrogen
Sulphuric acid + magnesium = magnesium sulphate + hydrogen
Magnesium reacts rapidly with acids because it easily form mg2+ ions
Mg = Mg2+ + 2e- oxidation
2H+ + 2e- = H2 reduction
Zinc
Hydrochloric acid + zinc = Zinc chloride + hydrogen
Sulphuric acid + zinc = zinc sulphate + hydrogen
Zinc reacts quite rapidly with acids
This is because zinc forms Zn2+ ions quite easily
Zn = Zn2+ + 2e- oxidation
2H+ + 2e- = H2 reduction
