REDOX REACTIONS

Question 1

Define oxidation. (1)

Answer 1

Oxidation refers to the loss of electrons by a substance, leading to an increase in its oxidation state. It often involves the addition of oxygen or loss of hydrogen.

Question 2

Define a redox reaction. (1)

Answer 2

where one substance loses electrons (oxidation) while another gains electrons (reduction).

Question 3

What is an oxidation state? (1)

Answer 3

indicate the number of electrons that an atom has gained or lost to form a chemical bond.

Question 4

What are oxidising agents? (1)

Answer 4

Substances that cause other substances to undergo oxidation are called oxidizing agents. They gain electrons themselves during the reaction.

Question 5

What are some examples of oxidation reactions? (3)

Answer 5

-Combustion reactions
-corrosion of metals
-biological oxidation (cellular respiration)

Question 6

What is the oxidation state of a compound? (1)

Answer 6

Always zero

Question 7

What is the oxidation state of oxygen? (1)

Answer 7

-2

Question 8

What are the exceptions to oxygens oxidation state? (1)

Answer 8

In peroxides such as H2O2 oxidation state is -1

Question 9

What is the oxidation state of hydrogen? (1)

Answer 9

+1

Question 10

What are the exceptions to hydrogens oxidation state? (1)

Answer 10

In metal hydrides such as NaH, oxidation state is -1

Question 11

Define reduction. (1)

Answer 11

Reduction refers to the gain of electrons by a substance, leading to a decrease in its oxidation state.

Question 12

What is meant by electron transfer? (1)

Answer 12

In a reduction reaction, electrons are gained by a substance. This can occur through the direct transfer of electrons from another substance or through the gain of electrons from an external source.

Question 13

What are reducing agents? (1)

Answer 13

Substances that cause other substances to undergo reduction are called reducing agents. They lose electrons themselves during the reaction.

Question 14

How does reduction alter oxidation states? (1)

Answer 14

Reduction leads to a decrease in the oxidation state of a substance.

Question 15

What are hydrogenation reactions? (1)

Answer 15

Reduction reactions often involve the addition of hydrogen atoms to unsaturated compounds, converting them into saturated compounds.

Question 16

How are reduction reactions important biologically? (1)

Answer 16

Reduction plays a crucial role in biological processes such as photosynthesis, where carbon dioxide is reduced to glucose in plants using energy from sunlight.

Question 17

Define disproportionation. (1)

Answer 17

Disproportionation is a type of redox reaction where the same element undergoes both oxidation and reduction within the same chemical reaction.

Question 18

What reactions are usually disproportionation? (2)

Answer 18

often involve an element in an intermediate oxidation state being converted to two different oxidation states. One species of the element is oxidized, while another is reduced.

Question 19

Why are disproportionation reactions important? (1)

Answer 19

are important in various industrial processes, such as the production of bleach and in biological systems, such as the decomposition of hydrogen peroxide in cells.

Question 20

What are some common oxidising agents? (3)

Answer 20

H2SO4, Al3+ and Cl2

Question 21

What are some common reducing agents? (4)

Answer 21

Na, O2-, I2 and H2O32-