Question

Why do elements combine? Calculate the number of molecules of sulphur ($S_8$ ) present in 16 g of solid sulphur. [3 MARKS]

Answer 1

Explanation - 1 Mark
Problem - 2 Marks

1. Elements combine to form chemical compounds and attain stability. For example, metals often react with nonmetals to form ionic compounds. These compounds are composed of positive and negative ions formed by adding or subtracting electrons from neutral atoms and molecules. Thus these compounds are stable in nature.

2. 1 mole of solid sulphur ($S_8$ ) = 8 x 32 g = 256 g

i.e., 256 g of solid sulphur contains = 6.022 x 10²³ molecules

Then, 16 g of solid sulphur contains = $6.022\times \frac{{10}^{23}}{256}\times 16$

= 3.76375 x 10²² molecules