Page 88 - Chemistry_Form_2

Chemistry
for Secondary Schools

Step 3: List the number of atoms on both sides
Reactants (left side):
H : 2 hydrogen atoms
2
Cl : 2 chlorine atoms
2
FOR ONLINE READING ONLY
Products (right side):
HCl: 1 hydrogen atom and 1 chlorine atom per molecule.
There are two hydrogen atoms and two chlorine atoms on the left but only one of
each on the right.

Step 4: Balance the equation
The HCl molecule contains one hydrogen atom and one chlorine atom on the
right side. Thus, two HCl molecules are required to balance for both hydrogen
atoms and chlorine atoms on the left.

Step 5: Verify the balancing
Count atoms of all elements on both sides to make sure they are equal.
Reactants (left side):

H : 2 hydrogen atoms
2
Cl : 2 chlorine atoms
2
Products (right side):

2HCl: 2 hydrogen atoms and 2 chlorine atoms.
Since the number of atoms is equal on both sides, the equation is balanced.

Steps 6: Write a balanced chemical equation
Write a balanced chemical equation with its state symbols.

2

Example 4.2
Zinc dissolves in dilute hydrochloric acid to form zinc chloride solution and
hydrogen gas. Write a balanced chemical equation for this reaction.

Step 1: Write the equation in word form

Student’s Book Form Two 81

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 81 01/08/2025 11:20:58
CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 81