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NCERT Class 10 Science Chemical Reactions and Equations: In-text questions (page 10) Solutions
AI-written, checked on 23 Oct 2026
Solutions written by Shishya, checked — not the board's official answers
Step-by-step working for every question of In-text questions (page 10) in NCERT's Class 10 Science book, chapter “Chemical Reactions and Equations”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.
How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.
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In-text (page 10) Q1
A substance X is used for whitewashing. (i) Name X and write its formula. (ii) Write its reaction with water.
- (i) The substance used for whitewashing is calcium oxide.
- (i) Its chemical formula is CaO.
- (ii) Calcium oxide reacts with water to form calcium hydroxide.
- (ii) The balanced chemical equation is CaO + H2O → Ca(OH)2.
why?
A balanced equation has the same number of atoms of each element on both sides, because atoms are neither created nor destroyed in a chemical reaction (law of conservation of mass). Only the numbers in front (coefficients) change, never the formulas.
Answer: (i) calcium oxide, CaO; (ii) CaO + H2O → Ca(OH)2
In-text (page 10) Q2
In the electrolysis of water (Activity 1.7), why is the gas collected in one test tube double the amount in the other? Name this gas.
- Water has the chemical formula H₂O, which means each molecule contains two hydrogen atoms and one oxygen atom.
- During electrolysis, water splits into hydrogen gas and oxygen gas in a 2:1 ratio by volume.
- Therefore, the test tube collecting hydrogen gas will have twice the volume of gas compared to the test tube collecting oxygen gas.
- The gas collected in the larger amount is hydrogen.
Answer: The gas collected in one test tube is double the amount in the other because water splits into hydrogen and oxygen in a 2:1 ratio by volume; the gas with the double amount is hydrogen.
Other exercises in this chapter
- In-text questions (page 6) — 3 questions
- In-text questions (page 13) — 3 questions
- End-of-chapter exercises — 20 questions
← Chemical Reactions and Equations: notes, practice and all exercises
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