5. Read the following and answer any four questions from (i) to (v) Oxidation has damaging effect on metals as well as on food. The damaging effect of oxidation on metal is studied as corrosion and that on food is studied as rancidity. The phenomenon due to which metals are slowly eaten away by the reaction of air, water and chemicals present in atmosphere, is called corrosion. For example, iron articles are shiny when new, but get coated with a reddish brown powder when left for sometime. This process is known as rusting of iron. Rancidity is the process of slow oxidation of oil and fat (which are volatile in nature) present in the food materials resulting in the change of smell and taste in them.

(i) Rancidity can be prevented by
(a) adding antioxidants
(b) packaging oily food in nitrogen gas
(c) both (a) and (b)
(d) none of these.
Ans: (c) both (a) and (b)
(ii) Combination of phosphorus and
oxygen is an example of

(a) oxidation
(b) reduction
(c) rancidity
(d) none of these.
Antioxidants and nitrogen gas prevent
oxidation of food.
4P + 3O2 → 2P2O3,
4P + 5O2 → 2P2O5
Ans: (a) oxidation
(iii) A science teacher wrote the following
statements about rancidity:
(I) When fats and oils are reduced, they
become rancid.
(II) In chips packet, rancidity is prevented
by oxygen.
(III)Rancidity is prevented by adding
antioxidants.
Select the correct option.
(a) (I) only
(b) (II) and (III) only
(c) (III) only
(d) (I), (II) and (III)
The oils and fats are slowly oxidised to certain
bad smelling compounds,
which release foul smell. This is known as
rancidity. Rancidity is prevented
by filling nitrogen gas in chips packets.
Ans: (c) (III) only
(iv) Two statements are given below
regarding rusting of iron.
(I) The rusting of iron is a redox reaction
and reaction occurs as,
(II) 4Fe + 3O2 → 4Fe3+ + 6O2–
(II) The metallic iron is oxidised to Fe2+
and O2 is reduced to O2–.
Select the correct statement(s).
(a) I only
(b) II only
(c) (c) Both I and II

(d) (d) None of these
Ans: (a) I only
(v) Which of the following measures can
be adopted to prevent or slow down
rancidity?
(I) Food materials should be packed in air
tight container.
(II) Food should be refrigerated.
(III)Food materials and cooked food
should be kept away from direct sunlight.
(a) Only II and III
(b) (b) Only I and III
(c) (c) Only II and III
(d) (d) I, II and III
Ans; (d) I, II and III