In this post we are going to share the detailed solution for class 10th science chapter 1. All the solutions are prepared by our esteemed teachers who are very well experienced in the teaching.
-
Complete Science Solutions Chapter Wise : Class 10th NCERT Science Solutions – All Chapters
Chapter 1 Solutions
EXERCISE :-1
QUE:-1. Why should a magnesium ribbon be cleaned before burning in air?
ANS:- Magnesium is very reactive metal it react with oxygen and form megnesium oxyde on the surface of megnesium ribbon like
Magnesium + Oxygen = Magnesium oxide
(Reactants) (Product)
Mg + O2 →2MgO
to remove megnesium oxyde layer from ribbon before burning it cleaned by sand paper so we get the surface of megnisium for burning .
QUE:-2. Write the balanced equation for the following chemical reactions.
(i) Hydrogen + Chlorine →Hydrogen chloride
(ii) Barium chloride + Aluminium sulphate →Barium sulphate +Aluminium chloride
(iii) Sodium + Water → Sodium hydroxide + Hydrogen
ANS:-
(i) H2 + Cl2 → 2HCl
(ii) 3 BaCl2 + Al2(SO4)3 → BaSO4 + 2 AlCl3
(iii) 2Na + 2H2O → 2NaOH + H2
QUE;-3. Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
ANS:-
(i) BaCl2 (aq) + Na2SO4 (aq) → BaSO4(s) + 2NaCl (aq)
(ii) NaOH (aq) + HCl(aq) → NaCl(aq) + H2O(l)
EXERCISE :-2
QUE:-1. A solution of a substance ‘X’ is used for whitewashing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X’ named in (i) above with water.
ANS:-
(i) The substance whose solution in water is used for white washing is calcium oxide (or quick lime). Its formula is CaO.
(ii) CaO +H2O(l) →Ca(OH)2
QUE:-2. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
ANS:- In Activity 1.7, water is electrolysed to give H2 gas at one electrode and O2 gas at the other electrode.
2H2O(l) → 2H2(g) + O2(g)
Thus two molecules of water on electrolysis give two molecules of hydrogen gas and one molecule of oxygen gas or in other words the amount of hydrogen gas collected would be double than that of oxygen gas.
EXERCISE :-3
QUE:-1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
ANS:- When an iron nail is dipped in copper sulphate solution, the displacement reaction takes place. The colour of copper sulphate solution fades due to the formation of light green solution of iron sulphate.
Fe(s) +CuSO4 →FeSO4 +Cu
QUE:-2. Give an example of a double displacement reaction other than the one given in Activity 1.10.
ANS:- Sodium hydroxide and hydrochloric acid react to form sodium chloride and water.
NaOH +HCl → NaCl +H2O(l)
QUE:-3. Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i) 4Na(s) + O2(g) →2Na2O(s)
(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
ANS:-
(i) Substances oxidised is Na as it gains oxygen and oxygen is reduced.
(ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen.
EXERCISE :-4 (CHAPTER END)
QUE:-1. Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) →2Pb(s) + CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all
ANS:- (i) (a) and (b)
QUE:-2. Fe2O3 + 2Al → Al2O3 + 2Fe The reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
ANS:- (d) Displacement reaction.
QUE:-3 . What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.
ANS:- (a) Hydrogen gas and iron chloride are produced.
QUE:- 4. What is a balanced chemical equation? Why should chemical equations be balanced?
ANS:- A balanced chemical equation has an equal number of atoms of different elements in the reactants and products.The chemical equations should be balanced to satisfy the law of conservation of mass .
QUE:-5. Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
ANS:- (a) 3H2 (g) + N2 (g) → 2NH3 (g)
(b) H2S (g) + 3O2 (g) → SO2 (g) + 2H2O(l)
(c) 3BaCl2 (aq) + Al2(SO4)3 (aq) → 2AlCl3 (aq) + 3BaSO4 ↓(s)
(d) 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)
QUE:-6. Balance the following chemical equations.
(a) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
(b) NaOH + H2SO4 → Na2SO4 + H2O
(c) NaCl + AgNO3 →AgCl + NaNO3
(d) BaCl2 + H2SO4 → BaSO4 + HCl
ANS:-
(a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O
(b) 2NaOH + H2SO4 → Na2SO4 + 2H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2 + H2SO4 → BaSO4 + 2HCl
QUE:-7 Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
ANS:-
(a) Ca (OH)2 + CO2 → CaCO3 + H2O
(b) Zn + 2AgNO3 → Zn(NO3)2 + 2 Ag
(c) 2Al + 3 CuCl2 → 2AlCl3 + 3 Cu
(d) BaCl2 + K2SO4 → BaSO4 + 2KCl
QUE:- 8. Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g) →Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)
ANS:-
(a) 2KBr (aq) + Bal2(aq) → 2Kl(aq) + BaBr2(s)
Type of reaction : Double displacement reaction
(b) ZnCO3 (s) → ZnO (s) + CO2 (g)
Type of reaction : Decomposition reaction
(c) H2 (g) + Cl2 (g) → 2HCl(g)
Type of reaction : Combination reaction
(d) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)
Type of reaction : Displacement reaction
QUE:-9 . What does one mean by exothermic and endothermic reactions? Give examples.
ANS:-
Exothermic reactions : Those reactions in which heat is evolved are known as exothermic reactions. An exothermic reaction is indicated by writing “+ Heat”on the products side of an equation.
Example :
(i) C (s) + O2 (g) → CO2 (g) + Heat
(ii) N2 (g) + 3H2 (g) → 2NH3 (g) + Heat
Endothermic reactions : Those reactions in which heat is absorbed are known as endothermic reactions. An endothermic reaction is usually indicated by writing “Heat” on the product side of a chemical equation.
Examples :
(i) C (s) + 2S (s) → CS2 (l) – Heat
(ii) N2 (g) + O2 (g) → 2NO(g) – Heat
QUE:- 10. Why is respiration considered an exothermic reaction? Explain.
ANS:-Respiration is an exothermic process because during respiration glucose combines with oxygen in the cells of our body to form carbon dioxide and water along with the production of energy.
C6 H12 O6 +6O2 →6CO2 +6H2 O + ENERGY
QUE:-11. Why are decomposition reactions called the opposite of combination reactions?Write equations for these reactions.
ANS :- In a decomposition reaction, a single compound breaks down to produce two or more simpler substances.
For example:
2H2 O(l) Elecricity(decomposition) →2H2 (g) +O2(g)
While, in a combination reaction, two or more substances simply combine to form a new substance.
For example:
2H2(g) +O2(g) combination→2H2 O(l)
QUE:-12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
ANS:-
CaCO3(s) (calcium carbonate) Heat → CaO(s) +CO2(g)
2 AgBr(s) (silver bromide) Light → 2Ag(s) + Br2(g)
2H2 O(l) Elecricity →2H2 (g) +O2(g)
QUE:-13. What is the difference between displacement and double displacement reactions?
Write equations for these reactions.
ANS:-
In displacement reactions, a more reactive metal displaces a less reactive metal from its solution. For example,
Fe(s) + CuSO4(aq) → Cu(s) + FeSO4(aq)
This is a displacement reaction where iron displaces copper from its solution.
In double displacement reactions, two reactants in solution exchange their ions. For example,
AgNO3(aq) + NaCl (aq) → AgCl(s) + NaNO3 (aq)
This is a double displacement reaction where silver nitrate and sodium chloride exchange Cl– and NO3– ions between them.
QUE:-14. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
ANS:-
2AgNO3 (aq)(siver nitrate)+Cu(s) (copper) → Cu(NO3)2(copper niterate) +2Ag(s)(silver)
QUE:-15. What do you mean by a precipitation reaction? Explain by giving examples.
ANS:-
A reaction in which an insoluble solid called precipitate is formed that separates from the solution is called a precipitation reaction.
Example : When a solution of iron (III) chloride and ammonium hydroxide are mixed, a brown precipitate of iron (III) hydroxide is formed.
QUE:-16 . Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
ANS:-
(a) Oxidation : The addition of oxygen to a substance is called oxidation.
Example :
(i) S(s) + O2(g) → SO2(g) (Addition of oxygen to sulphur)
(ii) 2Mg(s) + O2 (g) → 2MgO(s) (Addition of oxygen to magnesium)
(b) Reduction : The removal of oxygen from a substance is called reduction.
Example: (i) CuO + H2 Heat → Cu + H2O
Here, copper oxide is being reduced to copper because oxygen gets removed from copper oxide.
(ii) ZnO + C → Zn + CO
Here, zinc oxide is being reduced to zinc because oxygen gets removed from zinc oxide.
QUE:- 17. A shiny brown coloured element ‘X’ on heating in air becomes black in colour.
Name the element ‘X’ and the black coloured compound formed.
ANS:-
Element ‘X’ is copper (Cu).
The black coloured compound is copper oxide (CuO). The reaction involved is
QUE:-18. Why do we apply paint on iron articles?
ANS:-
Paint does not allow iron articles to come in contact with air, water and saves iron articles from damage due to rusting.
QUE:-19. Oil and fat containing food items are flushed with nitrogen. Why?
ANS:-
To keep food items fresh and save from getting oxidised, food items are flushed with nitrogen.
QUE:-20. Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
ANS:-
(a) Corrosion : It is the process in which metals are eaten up gradually by the action of air, moisture or a chemical (such as an acid) on their surface.
Example : When iron is exposed to moist air for a long period of time, its surface acquires a coating of a brown, flaky substance called rust. Rust is mainly hydrated iron (III) oxide [Fe2O3.xH20].
(b) Rancidity : The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called rancidity.
Rancidity spoils the food materials prepared in fats and oils which have been kept for a considerable time and makes them unfit for eating.
Rancidity can be prevented by adding anti-oxidants to foods containing fats and oils. It can also be prevented by flushing fat and oil containing foods with nitrogen before sealing.
SUMMARY:-
* A complete chemical equation represents the reactants, products and their physical
states symbolically.
* A chemical equation is balanced so that the numbers of atoms of each type involved
in a chemical reaction are the same on the reactant and product sides of the
equation. Equations must always be balanced.
* In a combination reaction two or more substances combine to form a new single
substance.
* Decomposition reactions are opposite to combination reactions. In a decomposition
reaction, a single substance decomposes to give two or more substances.
* Reactions in which heat is given out along with the products are called exothermic
reactions.
* Reactions in which energy is absorbed are known as endothermic reactions.
* When an element displaces another element from its compound, a displacement
reaction occurs.
* Two different atoms or groups of atoms (ions) are exchanged in double displacement
reactions.
* Precipitation reactions produce insoluble salts.
* Reactions also involve the gain or loss of oxygen or hydrogen by substances.
Oxidation is the gain of oxygen or loss of hydrogen. Reduction is the loss of oxygen
or gain of hydrogen.
You can see the other posts here :
- NCERT Class 10th Science Chapter 2- Acids, Bases and Salts Solutions
- NCERT Class 10th Science Chapter – 3 Metals and Non Metals
-
Complete Science Solutions Chapter Wise : Class 10th NCERT Science Solutions – All Chapters
Tags : class 10th science chapter 1 solutions, 10th class science solutions, 10th class solution, science class 10th, ncert class 10th solutions, chapter 1 class 10th science.
