Chapter 4 - Acids and redox

Question 1

Strong acids

Answer 1

➜ Completely dissociates in an aqueous solution
➜ e.g HCL
➜ (releasing all its H+ ions)

Question 2

Weak Acids

Answer 2

➜ Partially dissociates in an aqueous solution
➜ e.g ethanoic acid - CH3COOH
➜ (releasing a small proportion of its H+ ions)

Question 3

Bases

Answer 3

➜ Metal oxides
➜ metal hydroxides
➜ metal carbonates
➜ ammonia

Question 4

Alkali

Answer 4

➜ A base that dissolves in water releasing hydroxide ions

Question 5

General equations

Answer 5

ACID + METAL ➜ SALT + HYDROGEN (usually gas)

ACID + BASE ➜ SALT + WATER

ACID + CARBONATE ➜ SALT + WATER + CARBON DIOXIDE

Question 6

Oxidation Number

Answer 6

➜ A measure of the number of electrons that an atom uses to bind with atoms of another element.

Question 7

Rules for Elements

Answer 7

➜ Oxidation number is always ZERO for elements

➜ e.g H2, O2, P4, Na all ZERO

Question 8

Rules for compounds and Ions

Answer 8

➜ O = -2
➜ H = +1
➜ F = -1
➜ Na²⁺, k⁺ = +1
➜ Mg²⁺, Ca²⁺ = +2
➜ Cl⁻, Br⁻, I⁻ = -1

➜ H in metal hydrides = -1
➜ O in peroxides = -1
➜ O bonded to F = +2

Question 9

Roman Numerals

Answer 9

➜ e.g iron (II) = Fe²⁺ with oxidation number 2+

Question 10

Polyatomic ions containing oxygen

Answer 10

➜ No₂⁻ = nitrate = oxidation number is +3 = nitrate(III)

➜ No₃⁻ = nitrate = oxidation number is +5 = nitrate(V)

Question 11

Redox reactions

Answer 11

➜ Oxidation is the addition of Oxygen

➜ Reduction is the removal of Oxygen

Question 12

Redox reactions (e⁻)

Answer 12

➜ Reduction is the gain of e⁻

➜ Oxidation is the loss of e⁻

Question 13

Redox reactions (oxidation numbers)

Answer 13

➜ Reduction is a decrease in oxidation number

➜ Oxidation is an increase in oxidation number