Is Matter Around Us Pure Test - 16

Sulphur is insoluble in water, while common salt is soluble in water. Hence, the mechanical mixture of sulphur and common salt can be separated by making use of the solubility of salt in water.

The correct answer is B.

Why alternative A is wrong:

Slaked lime and quick lime are both soluble in water.

Why alternative C is wrong:

Sulphur and iron filings are both insoluble in water.

Why alternative D is wrong:

Sugar and salt are both soluble in water.

The change of a substance from its solid state to its gaseous state, directly, without forming a liquid, is called sublimation.

The correct answer is B.

Why alternative A is wrong:

The change from liquid to gaseous state, at a temperature that is less than the boiling point of the liquid, is known as evaporation.

Why alternative C is wrong:

Precipitation is the term used to describe rainfall.

Why alternative D is wrong:

In condensation, a change from a lighter to a denser state takes place (such as, from the gaseous state to the liquid state).

A mixture is said to be homogeneous if its composition is uniform throughout. For example, air is a homogeneous mixture that contains a number of gases.

The correct answer is D.

Why alternative A is wrong:

If the components of a mixture exist in more than one state then the mixture cannot be homogeneous as the composition will not be constant.

Why alternative B is wrong:

If the composition of a mixture is not uniform throughout, then the mixture cannot be homogeneous.

Why alternative C is wrong:

Homogeneous mixtures can be in solid, liquid or gaseous states.

In order to answer this question, the student should know the physical properties of various compounds that are to be distilled. Two miscible liquids can be separated from each other using simple distillation only if the difference between their boiling points is less than 25 K.

Hence, the correct answer is option A.

A homogeneous mixture consists of only one phase. This single phase may be gaseous, liquid, or solid.

The correct answer is A.

Why alternative B is wrong:

A homogeneous mixture consists of only one phase. However, it is not necessarily liquid. It can be solid or gaseous also.

Why alternative C is wrong:

A mixture that has two or more phases is known as a heterogeneous mixture.

Why alternative D is wrong:

A homogeneous mixture consists of only one phase.

A heterogeneous mixture comprises visibly different substances or phases. For example, the mixture of iron fillings and sulfur is heterogeneous as iron can be separated from the mixture by the simple application of a magnetic field on the mixture.

The correct answer is D.

Why alternative A is wrong:

Mixtures that have only one phase are known as homogeneous mixtures. A heterogeneous mixture always has two or more phases.

Why alternative B is wrong:

If the composition of a mixture is uniform throughout, then the mixture is said to be homogeneous, and not heterogeneous.

Why alternative C is wrong:

If the components of a mixture are not visible to the naked eye, then the mixture cannot be heterogeneous as the components of a heterogeneous mixture are visibly different from each other.

Brass is an alloy of copper and zinc. These two metals cannot be separated by physical methods as they exist in a single phase. Hence, brass is an example of a homogeneous mixture of metals.

The correct answer is D.

Why alternative A is wrong:

The mixture of iron and calcium is a heterogeneous mixture as iron and calcium can be separated by the application of a magnetic force.

Why alternative B is wrong:

The mixture of iron and copper is a heterogeneous mixture as iron and copper can be separated by the application of a magnetic force.

Why alternative C is wrong:

Iron, existing in its pure form, is an element, and not a mixture.

Brass is an alloy of copper and zinc. These two metals cannot be separated by physical methods as they exist in a single phase. Hence, brass is an example of a homogeneous mixture existing in the solid phase.

The correct answer is C.

Why alternative A is wrong:

The mixture of salt and chalk powder is a heterogeneous mixture as salt and chalk can be separated physically.

Why alternative B is wrong:

The mixture of iron and sulphur is a heterogeneous mixture as iron and sulphur can be separated physically.

Why alternative D is wrong:

Sand contains many particles and phases. Therefore, it is a heterogeneous mixture.

On constant stirring of milk, the fats suspended in milk coagulate and eventually separate.

The correct answer is D.

Why alternative A is wrong:

When sugar is dissolved in water, the mixture becomes one medium. Therefore, sugar dissolved in water is a homogeneous mixture, and not a mechanical one.

Why alternative B is wrong:

When salt is dissolved in water, the mixture becomes one medium. Therefore, salt dissolved in water is a homogeneous mixture, and not a mechanical one.

Why alternative C is wrong:

The components of petrol exist in a single phase. Therefore, petrol is a homogeneous mixture, and not a mechanical one.

Muddy water is a mechanical mixture. This mixture can be separated by simple physical methods.

The correct answer is D.

Why alternative A is wrong:

The components of petrol exist in a single phase. Therefore, petrol is a homogeneous mixture, and not a mechanical one.

Why alternative B is wrong:

The components of diesel exist in a single phase. Therefore, diesel is a homogeneous mixture, and not a mechanical one.

Why alternative C is wrong:

When salt is dissolved in water, the mixture becomes one medium. Therefore, saline water is a homogeneous mixture, and not a mechanical one.