Question 61 markMCQSection A

Select washing soda from the following:

Acids, Bases and Salts
Salts and their derivatives

Options

(a)NaHCO3\mathrm{NaHCO}_3
(b)Na2CO3⋅5H2O\mathrm{Na}_2\mathrm{CO}_3 \cdot 5\mathrm{H}_2\mathrm{O}
(c)Na2CO3⋅10H2O\mathrm{Na}_2\mathrm{CO}_3 \cdot 10\mathrm{H}_2\mathrm{O}
(d)NaOH\mathrm{NaOH}

Official answer

The correct option is (c). Washing soda is sodium carbonate decahydrate, represented by the chemical formula Na2CO3⋅10H2ONa_2CO_3 \cdot 10H_2O.

Answer keywords:Washing sodaSodium carbonate decahydrateNa2CO3.10H2O

Marking scheme

  1. 1.Identification of the correct option (c) (1 mark)

Hint

Washing soda is a sodium carbonate salt containing ten molecules of water of crystallization.

Quick oral answer

The chemical formula of washing soda is sodium carbonate decahydrate, written as Na2CO3⋅10H2ONa_2CO_3 \cdot 10H_2O.

Common mistakes

  1. 1.Confusing washing soda (Na2CO3⋅10H2ONa_2CO_3 \cdot 10H_2O) with baking soda (NaHCO3NaHCO_3).
  2. 2.Selecting the incorrect number of water molecules of crystallization (e.g., choosing 5H2O5H_2O instead of 10H2O10H_2O).

Analysis and explanation

Washing soda is a sodium-derived salt obtained by recrystallization of sodium carbonate. Its chemical formula is Na2CO3⋅10H2ONa_2CO_3 \cdot 10H_2O (sodium carbonate decahydrate), where the 10H2O10H_2O represents the ten molecules of water of crystallization.


  • Option (a) is incorrect because NaHCO3NaHCO_3 is the chemical formula for baking soda (sodium hydrogencarbonate).
  • Option (b) is incorrect because washing soda specifically contains ten molecules of water of crystallization (10H2O10H_2O), not five (5H2O5H_2O).
  • Option (d) is incorrect because NaOHNaOH is sodium hydroxide (caustic soda), which is a strong base, not a carbonate salt.

Interesting facts

The ten water molecules in washing soda are not 'wet' water; they are part of the crystal structure (water of crystallization) that gives the salt its crystalline shape.

Question details

Q6 of 39 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2023
Section
Section A
Marks
1
Type
MCQ
Chapter
Acids, Bases and Salts
Topic
Salts and their derivatives
Bloom's level
Remembering
Syllabus topic
Sodium compounds: Washing soda.

Spotted a mistake or something unclear?

Tell us and we will fix it.

Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2023?

This question carries 1 mark in the CBSE Class 10 Science 2023 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Acids, Bases and Salts" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Salts and their derivatives" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2023 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2023 paper.