Select washing soda from the following : (A) NaHCO_3 (B) Na_2CO_3.5H_2O (C) Na_2CO_3.10H_2O (D) NaOH

ScienceCBSE Class 10 · Board exam 2023, set 31/1/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 6

Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, section A, question 6, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q6 · 1 mark · MCQAcids, Bases and Salts

Select washing soda from the following :

(A) $NaHC O_{3}$
(B) $N a_{2} C O_{3} .5 H_{2} O$
(C) $N a_{2} C O_{3} .10 H_{2} O$
(D)NaOH

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Washing soda is made by recrystallising sodium carbonate.

Hint 2

How many water molecules of crystallisation does it contain?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

Washing soda is sodium carbonate decahydrate, which has 10 molecules of water of crystallisation.
Its formula is $N a_{2} C O_{3} .10 H_{2} O$ , which is option (C). $NaHC O_{3}$ is baking soda and NaOH is caustic soda.
1 mark

Answer: Option (C) Na₂CO₃·10H₂O

Where the marks are

Chooses $N a_{2} C O_{3} .10 H_{2} O$ (1 mark)

Revise the chapter

Chapter: Acids, Bases and Salts (notes, formulas, where marks are lost and every past question)
Topic: Baking Soda, Washing Soda and Plaster of Paris

Practise this chapterBoard-style questions from Acids, Bases and Salts, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/1/1: every question, by section.

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CBSE Class 10 Science 2023: question 6

Hints

Step-by-step solution

Revise the chapter

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