Question

(a) What do you see when a magnesium ribbon is burnt? Is magnesium oxidized or reduced in this reaction?
(b) Define corrosion?

Answer 1

Hint: Magnesium ribbons burn in air to form magnesium oxide and. Both magnesium and oxygen combine together to form magnesium oxide which is a white powder.
Corrosion is a type of combination reaction in which two or more elements or compounds combine to form a single compound.

Complete step by step answer:
First question:
Magnesium oxide gives two electrons to oxygen which leads to the formation of this white powder. Before identifying the oxidizing agent let’s understand what the basic terms like oxidation, reduction, oxidizing agent and reducing agent means.
Oxidation is the loss of electrons or it is the increase in the oxidation state of an element or addition of oxygen to an element or removal of hydrogen from an element.
Reduction is the gain of electrons or it is the decrease in the oxidation state of an element or addition of hydrogen to an element or removal of oxygen from an element.
An oxidizing agent is a substance which gains electrons and gets reduced which leads to the decrease in oxidation state. It oxidizes the other substance.
A reducing agent is a substance which loses electrons and gets oxidized which leads to the increase in oxidation state. It reduces the other substance.
The reaction followed is:
\[2Mg+{{O}_{2}}\to 2MgO\]
In the reaction metal oxide is oxidized to its metal oxide state hence it undergoes oxidation.
Second question:
A combination reaction is a type of reaction in which two or more elements or compounds combine to form a single compound corrosion is a type of combination reaction.
Corrosion is a process in which a refined metal is converted to convert it into a more stable form such as its oxides or hydroxides. This leads to the deterioration of the metal.
The general reaction is:
\[metal+{{O}_{2}}\to \text{metal oxide}\]

Note: In order to start the burning of magnesium ribbon it requires a source of energy, the flame provides a source of heat which acts as a source of energy. Activation energy is the minimum energy required for the completion of a chemical reaction.
Corrosion is a spontaneous and electrochemically favored reaction.it is a reduction-oxidation type of reaction. Examples- rusting of iron, tarnish of silver etc.