MODULE 2: Acids and Redox
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What is an acid?
A compound with aqueous hydrogen ions (not just any compound with hydrogen!)
What are strong acids?
Acids that completely dissociate their hydrogen ions
What are weak acids?
Acids that partially dissociate their hydrogen ions
What are bases?
A substance that neutralises an acid to form a salt
What is an alkali?
A base that when dissolved in water releases hydroxide ions (OH-)
What is neutralisation?
When the dissociated hydrogen ions from an acid react with the metal/ammonium ions of a base to form a salt and water
What is formed when acids are neutralised by carbonates?
Salt, water and carbon dioxide gas
What is titration?
A technique used to accurately measure the volume of one solution that reacts exactly with another solution, often used for neutralisation
What are the uses for titrations?
Finding the concentration of a solution, identification of unknown chemicals, finding the purity of a substance
What is the equipment needed for a titration?
Pipette, biurette and conical flask
What is an oxidation number?
The number of electrons involved in bonding to another element/compound
What is oxidation?
Loss of electrons/adding of oxygen
What is reduction?
Gain of electrons/removal of oxygen
When is the oxidation state zero?
When elements are in their natural state, when the sum of atoms in a compound adds to zero
What is the oxidation state of ions?
The charge is their oxidation number (H+ = +1)
What is the first rule of oxidation?
Oxidation number of elements from group 1, 2 or 3 is always +1, +2 or +3 respectively
What is the second rule of oxidation?
Oxidation number of fluorine is always -1
What is the third rule of oxidation?
Oxidation number of hydrogen is usually +1
What is the fourth rule of oxidation?
Oxidation number of oxygen is usually -2
What is the fifth rule of oxidation?
Oxidation number of chlorine is usually -1
How do roman numerals effect oxidation numbers?
The roman numeral shows the oxidation state without the sign (+/-)
What happens when the oxidation number increases?
Loss of electrons, more positive
What happens when the oxidation number decreases?
Gain of electrons, more negative
What are redox reactions?
A reaction where oxidation and reduction both occur