Question

Which of the following properties does not describe a compound?

A) It is composed of two or more elements

B) It is a pure substance

C) It cannot be separated into constituents by physical means

D) It is mixed in any proportion by mass

Answer 1

Hint: Matter is anything that occupies space and has mass. It is divided into two categories, mixtures and pure substances. Mixtures are divided into homogeneous mixtures and heterogeneous mixtures. Pure substances are further divided into elements and compounds.

Complete answer:

For the above question let us examine each option one by one.

We know that elements consist of only one type of particle. These particles can be singular atoms or molecules of that element. Now, when two or more atoms of different elements combine than we get the molecules of a compound. Hence option  $ A$  is correct.

As we saw above, matter is divided into mixtures and pure substances. These pure substances are further divided into elements and compounds. Hence option  $ B $  is also correct.

Compounds are chemical substances which form when atoms of different elements bind together. These chemical bonds are very strong and it is impossible to break these bonds through physical means. These bonds can only be broken down through chemical means (by chemical reaction of the compound to get the elements back). Hence option  $ C $  is incorrect.

In a compound, two or more elements combine chemically in a constant ratio by mass. This ratio is maintained even when the compound is broken down by chemical means. For example: in a water molecule, hydrogen and oxygen combine in a ratio of  $ 2:1 $  to form the  $ {H_2}O $  molecule. Hence, two hydrogen atoms and one oxygen atom in combination give one water molecule. Therefore option  $ D $  is incorrect.

Hence, option  $ C $  and option  $ D$  is incorrect.

Hence option (A) and (B) is correct.

Note:

Mixtures can be physically separated by means of filtration, sublimation, evaporation, magnetic separation etc. Physical separation does not cause change in the structure of a substance. Also remember that compounds only form during a chemical reaction. The numbers written below the symbols of different elements describe the exact number of atoms in the compound.