Home · Schooling · CBSE · Class 10 · Science · Chemical Reactions and Equations · In-text questions (page 13)
NCERT Class 10 Science Chemical Reactions and Equations: In-text questions (page 13) 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 13) 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.
Tap “why?” under a step to see the textbook rule it uses — from Shishya's fixed list of NCERT Class 9-10 rules, not written by AI for this page. A step without one has no rule from the list yet.
Stuck on a step?
Ask the AI tutor about this chapter — it gives hints before answers — or snap a photo of your own question to get worked steps. You will be talking to an AI, not a person. For ages 13 and up; the first answer of each is free.
In-text (page 13) Q1
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
- Iron is more reactive than copper, so it displaces copper from the copper sulphate solution.
why?
A more reactive metal displaces a less reactive metal from a solution of its salt (reactivity series); a less reactive metal cannot displace a more reactive one.
- The iron nail reacts with copper sulphate to form iron sulphate and copper metal.
- The copper metal deposits on the surface of the iron nail.
- The solution now contains iron sulphate, which is pale green in colour.
- The original blue colour of copper sulphate fades as the copper ions are removed from the solution.
Answer: The colour changes from blue to pale green because iron displaces copper, forming iron sulphate in the solution.
- Iron is more reactive than copper, so it displaces copper from the copper sulphate solution.
In-text (page 13) Q2
Give an example of a double displacement reaction other than the one in Activity 1.10.
- In a double displacement reaction two compounds exchange their ions to form two new compounds.
- Activity 1.10 uses sodium sulphate and barium chloride, so take a different pair: silver nitrate and sodium chloride solutions.
- When they are mixed, silver ions (Ag⁺) and chloride ions (Cl⁻) join to form a white precipitate of silver chloride, while sodium nitrate stays in solution.
- AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq).
Answer: AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq) (another example: Pb(NO₃)₂(aq) + 2KI(aq) → PbI₂(s) + 2KNO₃(aq))
In-text (page 13) Q3
Identify the substances oxidised and reduced: (i) 4Na(s) + O₂(g) → 2Na₂O(s) (ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l).
- (i) In the reaction 4Na(s) + O₂(g) → 2Na₂O(s), sodium (Na) gains oxygen.
- Sodium is therefore oxidised.
why?
Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.
- Oxygen combines with sodium; it is the substance that gets reduced (it is the oxidising agent).
why?
Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.
- Oxygen is reduced in this reaction.
why?
Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.
- (ii) In the reaction CuO(s) + H₂(g) → Cu(s) + H₂O(l), copper oxide (CuO) loses oxygen.
- Copper oxide is therefore reduced.
why?
Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.
- Hydrogen (H₂) gains oxygen to form water.
- Hydrogen is therefore oxidised.
why?
Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.
Answer: (i) Oxidised: Na, Reduced: O₂; (ii) Oxidised: H₂, Reduced: CuO
Other exercises in this chapter
- In-text questions (page 6) — 3 questions
- In-text questions (page 10) — 2 questions
- End-of-chapter exercises — 20 questions
← Chemical Reactions and Equations: notes, practice and all exercises
Saves these solutions in this browser on this phone. No sign-in; nothing about you is saved or sent. A saved copy is not updated until you save it again. Parts that load from the server when you use them (the AI tutor, adaptive practice, sign-in) still need a connection.