The formula of washing soda shows sodium carbonate decahydrate. What does the word decahydrate indicate?
Answer and explanation
Correct answer: Ten water molecules in the crystal
The prefix “deca-” means ten, and “hydrate” refers to water associated with a compound. Thus, sodium carbonate decahydrate, Na₂CO₃·10H₂O, contains ten water molecules of crystallisation for each formula unit of sodium carbonate. Therefore, option A is correct. The term does not indicate ten metals or ten acids, and it cannot mean that the crystal has no water. The water is present in a definite chemical ratio.
Frequently asked questions
What is the correct answer to this question?
Ten water molecules in the crystal
Why is this the correct answer?
The prefix “deca-” means ten, and “hydrate” refers to water associated with a compound. Thus, sodium carbonate decahydrate, Na₂CO₃·10H₂O, contains ten water molecules of crystallisation for each formula unit of sodium carbonate. Therefore, option A is correct. The term does not indicate ten metals or ten acids, and it cannot mean that the crystal has no water. The water is present in a definite chemical ratio.
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.
