Lecture 7

Question 1

What happens when magnesium burns?

Answer 1

Magnesium burns in air with a white flame.

Question 2

Magnesium Oxidation formula?

Answer 2

2Mg+ 02 = 2MgO
Magnesium is oxidised because it loses electrons and increases in oxidisation state from 0 to +2. Oxygen is reduced because it gains electrons and decreases in oxidation state from 0 to -2.

Question 3

What happens when hydrogen is passed over heated copper oxide?

Answer 3

The black compound turns pink

Question 4

Write the Reduction Formula for copper oxide reacting with hydrogen?

Answer 4

CuO + H2 = Cu + H2O

Question 5

What happens when calcium burns in air?

Answer 5

Calcium burns in air with a red flame and forms the white compound calcium oxide.

Question 6

Write the formula for calcium reacting with oxygen

Answer 6

2Ca + O2 = 2CaO

Question 7

What is a oxidizing agent?

Answer 7

A substance that gains electrons and is thereby reduced to a low valency state.

Question 8

What is a reducing agent?

Answer 8

A substance that loses electrons and is thereby oxidized to a higher valency state.

Question 9

What is the formula and half equations of sodium reacting with chlorine?

Answer 9

2Na + Cl2 = 2NaCl
Na = Na+ + e-
Cl2 + 2e- = 2Cl-

Question 10

What is an oxidation number?

Answer 10

A number given to each atom or ion in a compound that shows us its degree of oxidation. It can be +,- or 0.

Question 11

What is hydrogens usual oxidation state in compounds?

Answer 11

+1

Question 12

What is sodium and other group 1 metals usual oxidation state in compounds?

Answer 12

+1

Question 13

What is calcium and group 2 metals usual oxidation state in compounds?

Answer 13

+2

Question 14

What is Aluminium usual oxidation state in compounds?

Answer 14

+3

Question 15

What is chlorine and group 7 metals usual oxidation state in compounds?

Answer 15

-1

Question 16

What is oxygen usual oxidation state in compounds?

Answer 16

-2

Question 17

Why does fluorine show a -1 oxidation number?

Answer 17

Fluorine is the most electronegative halogen, meaning it has strong attraction for electrons. When fluorine chemically bonds to another element, it pulls the shared electrons towards itself, creating a partial negative charge.

Question 18

Why is fluorine an excellent oxidizing agent?

Answer 18

It can easily accept electrons to achieve a stable electron configuration.

Question 19

Difference between oxidation state and oxidation number?

Answer 19

Oxidation state refers to the actual charge of an atom however oxidation number is the hypothetical charge assigned to an atom due to a set of rules.

Question 20

What are the applications of redox reactions ?

Answer 20

Battery- used for generating DC current. Storage cells are used in vehicles to supply all the electrical needs.
Combustion- explosions
Photosynthesis- conversion of water and C02 into carbohydrates.
Production of chemicals based on electrolysis such as chlorine.
Sanitising water and bleaching materials.
Electroplating