CIE Coordinated Science: 7.2 Redox

CIE Coordinated Science: 7.2 Redox

​Take a look at your notes from C4 stoichiometry and C5 electricity & chemistry, remind yourself of the following:

​

• ​Chemical formulae

• ​Ionic charges

• ​OILRIG

• ​Half-equations

​

CIE Coordinated Science: 7.2 Redox

CIE Coordinated Science: 7.2 Redox

​Page 39 of the CIE 0654 syllabus

CIE Coordinated Science: 7.2 Redox

CIE Coordinated Science: 7.2 Redox

​How to identify redox reactions and how to find the reducing or oxidising agent.

Multiple Choice

When a substance is oxidised it will:

• Gain electrons

• Gain protons

• Lose electrons

• Lose protons

Multiple Choice

The oxidizing agent is the substance that:

• Gains protons

• Loses protons

• Gains electrons

• Loses electrons

CIE Coordinated Science: 7.2 Redox

​1. Assign oxidation numbers (charges) to reactant atom.

​

​Cu = +2

​O = -2

​H₂ = 0

​

​Copper(II) Oxide - Roman numerals tell us the charge which gives us the oxidation state.

​Hydrogen - this is the natural state of H which means the oxidation state = 0.

CIE Coordinated Science: 7.2 Redox

2. Assign oxidation numbers (charges) to product atoms:

​

​Cu = 0

​O = -2

​H₂ = +1

​

​Copper - elements are always 0.

​Hydrogen - is always +1 unless bonded to a metal .

​Oxygen - is always -2.

CIE Coordinated Science: 7.2 Redox

3. Compare the oxidation state changes:

​

​Cu: +2 to 0

​Reduction - number decreases

​

​H: 0 to +1

​Oxidation - number increases

CIE Coordinated Science: 7.2 Redox

4. Identify the reducing and oxidising agents.

​

​Cu: +2 to 0

​Reduction - number decreases

​This is the OXIDISING AGENT

​

​

​H: 0 to +1

​Oxidation - number increases

​This is the REDUCING AGENT

Multiple Choice

Defined as the gain of electrons.

• oxidation

• redox

• reduction

• LEO GER

Multiple Choice

Cl₂ + 2e- --> 2Cl ^- is an example of:

• a chemical reaction

• redox

• oxidation

• reduction

Multiple Choice

An increase in oxidation number.

• more acidic

• reduction

• less basic

• oxidation

Multiple Choice

Substance that oxidises another substance by accepting its electrons.

• reducing agent

• oxidation number

• combustion

• oxidising agent

Multiple Choice

Which is the correct half-equation of this reaction: 2Na + Cl₂ --> 2NaCl 

• Cl₂ + e^- --> 2Cl^-

• 2Cl - e^- --> Cl₂

• Na --> Na⁺ + e^-

• Na⁺ + Cl^- --> NaCl

Multiple Choice

What is the reducing agent here: N₂ + 3H₂ --> 2NH₃

• N₂

• H_2

• NH₃

• 2NH₃

Multiple Choice

Substance that reduces another substance by losing electrons.

• reducing agent

• half-reaction

• electronegative atom

• oxidizing agent

Multiple Choice

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D