NCERT Class 9 Science Solutions: Chapter 3 –Atoms and Molecules Part 2

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Image of Sodium Oxide for Atoms and Molecules

Image of Sodium Oxide for Atoms and Molecules

Question 1:

Q. Write down the formulae of

(i) Sodium oxide

A. Sodium oxide

(ii) Aluminium chloride

A. Aluminium chloride

(iii) Sodium sulfide

A. Sodium sulfide

(iv) Magnesium hydroxide

A. Magnesium hydroxide

Question 2:

Write down the names of compounds represented by the following formulae:

(i)

A. Aluminium sulphate

(ii)

A. Calcium chloride

(iii)

A. Potassium sulfate

(iv)

A. Potassium nitrate

(v)

A. Calcium carbonate

Question 3:

Q. What is meant by the term chemical formula?

A. The chemical formula of a compound means the symbolic representation of the composition of a compound. From the chemical formula of a compound, we can know the number and kinds of atoms of different elements that constitute the compound. For example, from the chemical formula of carbon dioxide, we come to know that one carbon atom and two oxygen atoms are chemically bonded together to form one molecule of the compound, carbon dioxide.

Question 4:

Q. How many atoms are present in a

(i) Molecule and

A. In a Molecule, three atoms are present; two of hydrogen and one of sulphur.

(ii) Ion?

A. In an ion, five atoms are present; one of phosphorus and four of oxygen.

Question 1:

Q. Calculate the molecular masses of,,,, , , ,, .

A. Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

Molecular mass of

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