Calculate the percentage mass of water in crystals of washing soda.
Answers
The percentage mass of water in crystals of washing soda is 63.38 %
• Washing soda crystals contain water of crystallisation. The chemical formula for the same is Na₂CO₃.10H₂O.
• The percentage mass of water in crystals of washing soda is given by the ratio of mass of water present in a crystal to the total mass of the crystal, multiplied by 100.
• Molecules of water present in a crystal = 10
Therefore, mass of water present in a crystal = 10 × mass of each molecule of water
= 10 × (2 g +16 g) [ H = 1 g, O = 16 g ]
= 10 × 18 g
= 180 g
• Mass of one crystal of washing soda (Na₂CO₃.10H₂O) = (2 × 22 g) + 12 g + (3 × 16 g) + 180 g
= 44 g + 12 g + 48 g + 180 g
= 284 g
• Therefore, percentage mass of water in a crystal of washing soda = (180 g / 284 g ) × 100 %
= 63.38 %
Percentage mass of water in crystals of washing soda = 63.38%
Explanation:
The chemical formula of washing soda is Na₂CO₃.10H₂O.
Molar mass of water in one molecule of washing soda = 10 * molar mass of water, as each molecule of washing soda contains 10 water molecules.
= 10 × (2 +16)
= 180 g
Molar Mass of washing soda (Na₂CO₃.10H₂O) = (2 × 22) + 12 + (3 × 16) + 180
= 284 g
The percentage mass of water in crystals of washing soda = mass of water present in a crystal / total mass of the crystal * 100.
= (180 / 284) * 100
= 63.38%