Ch 1 Chemical Reactions and Equations Class 10 Important Questions | NCERT Science Chapter-1

Ch 1 Chemical Reactions and Equations Class 10 Important Questions

The start of class 10 marks the beginning of the foundation for class 11 and class 12. It is very important study the basics in order to understand each and every chapter properly. In this page, we have provided all the important question for cbse class 9 that could be asked in the examination. Students also need to study the ncert solutions for class 10 in order to gain more knowledge and understanding the lessons. Questions and Answers are way to learn the new things in a proper way. NCERT textbooks downloads for class 9 in pdf are also available for the students if they need more help. By downloading these books, they can study from it. Our experts also prepared revision notes for class 9 so that students should see the details of each and every chapters. Class 9 important questions are the best to revise all the chapters in the best way.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it? Write chemical equation for the reaction involved. 
Answer

Iron is more reactive than copper so it displaces copper from copper sulphate solution and forms iron sulphate, hence the colour of solution changes.Equation: Fe + CuSO₄ (aq) → FeSO₄ (aq) + CuO 

Q2. State reason for the following: (i) Potato chips manufactures fill the packet of chips with nitrogen gas. (ii) Iron articles are shining when new, but get coated with a reddish brown powder, when left for some time. 
Answer

(i) Potato chips manufactures fill the packet of chips with nitrogen gas to prevent rancidity.(ii) Rusting and corrosion. 

Q3. A student prepares aqueous solutions of the following salts: Copper sulphate : ferrous sulphate, Sodium sulphate, barium chloride. Write the colour of each solution thus formed. 
Answer

Copper sulphate — Green Ferrous sulphate — Pale green Sodium sulphate — Milky white Barium chloride — White 

Q4. Barium chloride reacts with aluminium sulphate to give, aluminium chloride and barium sulphate.(i) State the two types in which the above reaction can be classified. (ii) Translate the above statement into a chemical equation. 
Answer

(i) Double displacement reaction and Precipitation reaction. (ii) 3BaCl₂ + Al₂(SO₄)₃ → 2AlCl₃ + 3BaSO₄(↓)

Short Answer Questions-II (SAQs-II): 3 Marks

Q1. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity.
Answer

(i) Decomposition by heat of lead nitrate.

(ii) Decomposition by light of Silver Chloride

(iii) Decomposition by electricity of Water

Q2. State the kind of chemical reactions in the following examples in terms of loss and gain of energy:
(i) Digestion of food in stomach 
(ii) Combustion of coal in air 
(iii) Heating of limestone.
Answer

Digestion of food in StomachC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + EnergyEnergy is released in the process. It is exothermic reaction.Combustion of CoalCoal is Carbon. It is a combustion reaction.C+O₂→CO₂Energy is released in the process hence it is known as exothermic reaction.Heating of Limestone. Limestone is calcium carbonate. Ca₂CO₃

Energy is absorbed in the process. So, the reaction is endothermic reaction.

Q3. A solution of a substance ‘X’ is used for testing carbon dioxide. Write the equation of the reaction of X with carbon dioxide. (b) How is X obtained? Write chemical equation.
Answer
(a) Substance X is lime water which is aqueous solution of Calcium Hydroxide. Ca(OH)₂ (aq)+CO₂ (g)→CaCO₃ (s)+H₂O(l)When limewater reacts with Carbon di oxide, it turns milky, that is Calcium Hydroxide.
(b) Calcium oxide reacts vigorously with water to produced slaked time (calcium hydroxide) releasing a large amount of heat.

Q4. Write the steps for balancing the chemical equation for the formation of ammonia by the combination of nitrogen and hydrogen.
Answer
First, we write the skeletal chemical equation for the process.N₂+H₂→NH₃Examine the number of atoms of different elements present in the unbalanced equation.In the above reaction both the sides Nitrogen and Oxygen both are unbalanced.To balance hydrogen, H₂ is multiplied by 3 LHS. It makes 6H-atoms on the left hand side. Now, to balance hydrogen, in RHS, 2 is multiplied to NH3. Nitrogen is balanced automatically. N₂ (g)+3H₂ (g)→2NH₃ (g)

Long Answer Questions (LAQs): 5 Marks

Q1. (a) Explain the term “rancidity.” Name the type of chemical reaction responsible for causing rancidity and define it. (b) Write three methods for preventing rancidity of food.
Answer
We have seen food getting contaminated and having an unpleasant smell if it is left open in summer.  In a hot weather, Oil present in food get oxidized and become Rancid. Such food is not recommended for consumption. The food is getting oxidized so the reaction is oxidation reaction.Methods for preventing food from getting oxidized are:-(a) Food is kept in cool place like refrigerator.(b) Packaging should be air tight(c) Antioxidants should be added to food.

Q2. (a) List any three observations that determine that a chemical reaction has taken place. Also list three informations that cannot be obtained about a chemical reaction, merely by its chemical equation.(b) Balance the following chemical equations.(i) Fe + H₂O → Fe₃O₄ + H₂(ii) CO₂ + H₂O → C₆H₁₂O₆+O₂
Answer
The three observations are(i) Change of color(ii) Change of temperature(iii) Evolution of Gas The three informations are Atmospheric conditions(i) Catalyst involved(ii) Physical states of reactants and productsBalancing Equations(i)  3Fe+4H₂O→Fe₃O₄+4H₂(ii)  6CO₂+6H₂O→C₆H₁₂O₆+6O₂

Important Links

NCERT Quick Revision Notes- Ch 1 Chemical Reactions and Equations 

NCERT Solution- Ch 1 Chemical Reactions and Equations 

Important MCQs- Ch 1 Chemical Reactions and Equations 

For Free, Video Lectures Click here