Page 76 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

dioxide molecule, the ratio of carbon atoms to oxygen atoms is
always 1 : 2. Thus carbon dioxide molecule can be represented CO
2
as CO . This type of representation is known as the chemical
2
formula of the compound. H O
2
The table shows some molecules and the atoms present in them.
Try to find more examples.

Molecule Atoms present Chemical formula
Carbon dioxide Carbon - 1 CO
2 CH
4
Oxygen - 2
Models of carbon dioxide,
Water Hydrogen - 2 H O
2 water and methane molecules.
Oxygen - 1 - Fig. 5.4 (a)
Table 5.9

• The chemical formula of sulphuric acid is H SO . How many
2 4
hydrogen atoms are present in one molecule of sulphuric acid?

• How many sulphur atoms are present? How about oxygen
atoms?

• Altogether, how many atoms are present?
What if it is 2H SO ?
2 4
Determine the total number of atoms present in the molecules Ball and stick model of
given below. methane (CH )
4
Fig. 5.4 (b)
$ CO $ 2C H O
2 12 22 11
$ 5H O $ 3NaCl
2
$ 7NH $ ZnCl
3 2
Chemical Equations
Write the symbol of the element, zinc.
What is the chemical formula of hydrochloric acid?

You have seen earlier the reaction between hydrochloric acid
and zinc. What are formed as a result of this reaction?

The substances taking part in a chemical reaction are called the
reactants. Substances formed as a result of the reaction are called Different molecular
models can be
the products.
produced using
Note down the reactants and the products in the reaction given ghemical in IT @
schoolEdubuntu.
above.

Basic Science VIII
Basic Science VIII 75 75