chemistry (6 to 10 are case study)

Rusting of an article made up of iron is called

• corrosion and it is a physical as well as chemical change

• dissolution and it is a physical change

• corrosion and it is a chemical change

• dissolution and it is a chemical change.

A mixture of sulphur and carbon disulphide is

• heterogeneous and shows Tyndall effect

• homogeneous and shows Tyndall effect

• heterogeneous and does not show Tyndall effect

• homogeneous and does not show Tyndall effect.

ASSERTION:- Alloys are homogenous mixtures

REASON:- Alloys can not be separated into their components by physical methods

• Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

• Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

• Assertion (A) is true but reason (R) is false.

• Assertion (A) is false but reason (R) is true.

Assertion: Oxygen is an element.

Reason: It cannot be decomposed by a physical or a chemical process.

• Both A and R are true and R is the correct explanation of A.

• Both A and R are true but R is not the correct explanation of A.

• A is true but R is false.

• A is false but R is true.

Assertion : True solution exhibits Tyndall effect.

Reason : Particles are very large in size.

• Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

• Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

• Assertion (A) is true but reason (R) is false.

• Assertion (A) is false but reason (R) is true.

We take some ammonium chloride in a china dish and place the china dish on a tripod stand (see Figure). The china dish is covered with an inverted glass funnel. A loose cotton plug is put in the upper, open end of the funnel to prevent the ammonium chloride vapours from escaping into the atmosphere. The china dish is heated by using a burner. On heating, ammonium chloride changes into white vapours. These vapours rise up and get converted into solid ammonium chloride on coming in contact with the cold, inner walls of the funnel (see Figure). In this way, ammonium chloride collects on the inner sides of the funnel in the form of a sublimate and can be removed.

What name is given to the phenomenon which takes place ?

• condensation

• evaporation

• sublimation

• vaporization

One of the following does not undergo sublimation. This one is :

• iodine

• sodium chloride

• ammonium chloride

• camphor

The conversion of a solid into vapors without passing through the liquid state is called :

• vaporisation

• fusion

• sublimation

• freezing

When heat is constantly supplied by a burner to boiling water, then the temperature of water during vaporisation :

• rises very slowly

• first rises and then becomes constant

• rises rapidly until steam is produced

• does not rise at all

During summer days, water kept in an earthen pot (pitcher) becomes cool because of the phenomenon of :

• diffusion

• transpiration

• osmosis

• evaporation