Unit 3 Chapter 5: Redox reactions

Question 1

What is a redox reaction?

Answer 1

transfer of electrons; one reactant loses electrons accepted by the other reactant

Question 2

Oxidation

Answer 2

loss of electrons

Question 3

Reduction

Answer 3

gain of electrons

Question 4

Oxidising agent (oxidants)

Answer 4

cause oxidation of another substance (are reduced in the process)

Question 5

Reducing agent (reductant)

Answer 5

cause reduction of another substance (are oxidised in the process)

Question 6

Metal reactivity series

Answer 6

• represents relative reactivity of metals by listing half-equations involving metals and corresponding cations
• stronger oxidising agents (more easily reduced) are lower in series

Question 7

Metal displacement reactions

Answer 7

involve transfer of electrons from more reactive metal to positive ions of less reactive ion in solution

Question 8

Dry corrosion

Answer 8

oxidation of a metal by oxygen gas

Question 9

Wet corrosion

Answer 9

oxidation by oxygen gas and water

Question 10

Oxidation number of a free element

Answer 10

0

Question 11

Oxidation number of a simple ion

Answer 11

The charge on the ion

Question 12

Oxidation number of elements in compounds

Answer 12

fixed with exceptions

Question 13

Oxidation number of main group metals in compound (exception 1)

Answer 13

Charge on ions

Question 14

Oxidation number of hydrogen in compound (exception 2)

Answer 14

• +1 with non-metals

- -1 with metals

Question 15

Oxidation number of oxygen in compound (exception 3)

Answer 15

• positive in compounds with fluorine

- -1 in peroxides

Question 16

Oxidation number of halogen in compound (exception 4)

Answer 16

• Fluorine = -1

- Cl, Br, I = -1 except in compounds with oxygen or other halogen above them

Question 17

Sum of oxidation numbers in neutral compound

Answer 17

= 0

Question 18

Sum of oxidation numbers of all atoms in polyatomic ion

Answer 18

= charge on ion

Question 19

What does the most electronegative element have?

Answer 19

negative oxidation number

Question 20

Increase in oxidation number means

Answer 20

oxidation has occurred

Question 21

Decrease in oxidation number means

Answer 21

reduction has occurred

Question 22

No change in oxidation number means

Answer 22

is not a redox reaction

Question 23

Conjugate redox pair

Answer 23

an oxidising agent (reactant) and reducing agent (product)

Question 24

Reducing agent (out of 4)

Answer 24

• Loses electrons
• Reduces oxidising agent
• Undergoes oxidation
• Reactant in oxidation half-equation

Question 25

Oxidising agent (out of 4)

Answer 25

• Accepts electrons
• Oxidises reducing agent
• Undergoes reduction
• Reactant in the reduction half-equation

Question 26

Steps for balancing redox half equations (out of 5)

Answer 26

1. Balance all atoms except O and H
2. Balance O atoms by adding H2O molecules to one side of half-equation
3. Balance H atoms by adding H+ ions to one side of half-equation
4. Balance charge on both sides of half-equation by adding electrons to more positive side
5. Indicate state of substance

Question 27

To construct overall equation from half equations

Answer 27

add oxidation half-equation and reduction half-equation (number of electrons used in reduction = electrons released in oxidation)