Acids and redox

Question 1

What is the definition of an acid?

Answer 1

A proton donor in aqueous solution

Proton = H+

Question 2

What is the definition of a base and give 4 examples?

Answer 2

A proton acceptor which neutralises an acid to form a salt

Examples: metal oxides, metal hydroxides, metal carbonates and ammonia (NH3)

Question 3

What is the definition of an alkali?

Answer 3

A base that dissolves in water to produce hydroxide ions

e.g. NaOH (aq) –> Na+ (aq) + OH- (aq)

Question 4

What is the definition of a strong acid?

Answer 4

An acid which fully dissociates in aqueous solution (all the acid molecules become ions)

Question 5

What is the definition of a weak acid?

Answer 5

Weak acids don’t fully dissociate in aqueous solution (shown with a reversible arrow in equations, most organic acids are weak)

Question 6

What is the definition of a salt?

Answer 6

The product of a base neutralising an acid (hydrogen ions from acid replaced by metal/ammonium ions)

Question 7

How do you recognise an organic acid?

Answer 7

It will contain carbon

Question 8

How do all organic acids behave?

Answer 8

The H at the end of the acid is the one which is lost

e.g. CH3CH2COOH (aq) –>

Question 9

How do you write organic salts?

Answer 9

With the metal at the end so the charges can be closer together

e.g. CH3COO-Na+

Question 10

What are the 5 rules for oxidation numbers?

Answer 10

1. Oxidation number of any element is 0
2. Oxidation number of monatomic ions equals the charge on the ion (e.g. Cl- = -1)
3. Oxidation number of oxygen in a compound is -2 and hydrogen is +1
4. Oxidation number of halides in IONIC compounds is -1 but can be different in COVALENT compounds
5. Oxidation number of all atoms in an uncharged compound added together equal 0 whilst in a polyatomic ion they equal the charge on the ion

Question 11

What are the exceptions in oxidation rules?

Answer 11

1. Hydrogen peroxide (H2O2) where O = -1
2. F2O where O = +2
3. NaH where H = -1 (hydrogen is always +1 apart from when bonded to a METAL)

Question 12

How do you decide what is oxidised/reduced in a reaction?

Answer 12

If oxidation number INCREASES –> oxidation

If oxidation number DECREASES –> reduction

Question 13

What is disproportionation?

Answer 13

When the same element is both oxidised and reduced

Question 14

Which substances are the reducing/oxidising agents in a redox reaction?

Answer 14

Reducing agent gets oxidised, oxidising agent gets reduced

Question 15

What do the numerals show in ions with oxygen?

Answer 15

The oxidation state

e.g. nitrate (V) = NO3-
+5