How many molecules of water of crystallisation are present in one molecule of washing soda?
Answer and explanation
Correct answer: 10
Washing soda has the formula \(\mathrm{Na_2CO_3\cdot10H_2O}\). The term \(10\mathrm{H_2O}\) shows that each formula unit of sodium carbonate is associated with 10 molecules of water of crystallisation. Therefore, option A is correct. Five water molecules occur in copper sulfate pentahydrate, \(\mathrm{CuSO_4\cdot5H_2O}\), not in washing soda. Exam tip: In a hydrated salt formula, the coefficient before \(\mathrm{H_2O}\) after the dot gives the number of water molecules of crystallisation.
Frequently asked questions
What is the correct answer to this question?
10
Why is this the correct answer?
Washing soda has the formula \(\mathrm{Na_2CO_3\cdot10H_2O}\). The term \(10\mathrm{H_2O}\) shows that each formula unit of sodium carbonate is associated with 10 molecules of water of crystallisation. Therefore, option A is correct. Five water molecules occur in copper sulfate pentahydrate, \(\mathrm{CuSO_4\cdot5H_2O}\), not in washing soda. Exam tip: In a hydrated salt formula, the coefficient before \(\mathrm{H_2O}\) after the dot gives the number of water molecules of crystallisation.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
