Question

Question 1 A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.

Class 9 - Science - Atoms and Molecules Page 43

Answer 1

Mass of the compound = 0.24g
Mass of boron = 0.096g
Mass of oxygen = 0.144g
Percentage of Boron = Mass of boron/ Mass of compound ×100
=0.096g/0.24g×100
=40%
Percentage of oxygen= Mass of oxygen/ masys of compound ×100
=0.144g/0.24g×100=60%
Alternative method
Percentage of oxygen = 100 - percentage of boron
=100-40
=60%

Answer 2

Answer:mark it as expert answer

Total mass of compound = 0.24 g

Mass of boron in it = 0.096 g

Therefore % composition by weight of boron = (Mass of boron/ Total mass of compound)*100

= (0.096/0.24)*100

= 40 %

Mass of oxygen in the compound = 0.144 g

Therefore % composition by weight of oxygen = (Mass of oxygen/ Total mass of compound)*100

= (0.144/0.24)*100

= 60 %.

The compound is made up of only boron and oxygen, therefore the % composition of the componenets sum to 100% (60% + 40%)