EASY
Earn 100

Describe the phenomena of rancidity.

Important Questions on Chemical Reactions and Equations

EASY
 Which of the following gases can be used for storage of fresh sample of an oil for a long time?
MEDIUM

Write the short note on:

Corrosion

MEDIUM
Fatty foods become rancid due to process of 
HARD

In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution:

(A) exchange of atoms takes place.

(B) exchange of ions takes place.

(C) a precipitate is produced.

(D) an insoluble salt is produced.

The correct option is:

EASY
Which gas is used as preservatives in the juice of fruits, in jam, and drying of fruits?
MEDIUM
Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light, and electricity.
MEDIUM
What is observed when a pinch of sodium hydrogen carbonate is added to 2 mL of acetic acid taken in a test tube? Write the chemical equation for the reaction involved in this case. 
MEDIUM
Silver articles when exposed to the air gradually turn blackish. Give reason.
MEDIUM
Manufacture of chips, flush the packets of chips with nitrogen gas. Why?
EASY
What is observed when a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube ? Write equation for the chemical reaction involved and name the type of reaction in this case.
EASY

Oil and fat containing food items are flushed with nitrogen. Why? 

HARD
1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the colour of the products formed in each case.
MEDIUM
The colour of NO2 and PbO formed when lead nitrate is heated are:
EASY
On heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O2 and a brown gas X is formed.
(a) Identify the type of reaction and the gas X.
(b) Write balanced chemical equation of the reaction.
(c) Write the pH range of aqueous solution of the gas X.
MEDIUM

When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a :

HARD
What would a student report nearly after 30 minutes of placing duly cleaned strips of aluminium, copper, iron and zinc in freshly prepared iron sulphate solution taken in four beakers?
MEDIUM

Write the short note on:

Rancidity

MEDIUM
Which gas is used as preservative in fruit juice and jams?