Ncert Class 10 Science Chapter 1 Chemical Reactions Equations

Chapter practice

1. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction.

1. KCL(aq) + AgNO3(aq)--------> AgCl(s) + KNO3(aq)
2. It is a double displacement reaction. It is also a precipitation reaction as AgCl is a white precipitate.

2. Write the balanced chemical equations for the following reactions.

1. (a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogen-carbonate.
2. (b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
3. (c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2I2), liberates iodine gas and also forms potassium sulphate.

3. Why do fireflies glow at night?.

1. It is because protein present in fireflies undergoes oxidation in presence of air and an enzyme. This chemical reaction involves emission of visible light. Therefore, fireflies glow at night.

4. Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?.

1. Grapes when attached to plants are living and therefore they have their immune system due to which they cannot get fermented. When microbes attack plucked grapes in absence of air, they undergo fermentation to form alcohol. This is a chemical process.

5. A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.

1. The substance ‘X’ is calcium oxide (CaO), element is calcium. Calcium oxide is used in cement industry. Calcium is present in bones in form of calcium phosphate. Calcium oxide dissolves in water forming alkali which turns red litmus blue. CaO(s)

6. Why do we store silver chloride in dark coloured bottles?

1. It is because silver chloride decomposes to silver and chlorine gas in presence of sunlight.
2. 2AgCl(s) ----------------> 2Ag(s) + Cl2(g)

7. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound

1. Write the chemical formulae of X and Y.
2. Write a balanced chemical equation, when X is dissolved in water.
3. 2Mg(s) + O2(g) ------------> 2MgO(s) + light
4. MgO(s) + H2O(l) ----------> Mg(OH)2(aq)

8.Which among the following changes are exothermic or endothermic in nature?

1. Decomposition of ferrous sulphate
2. Dilution of sulphuric acid
3. Dissolution of sodium hydroxide in water
4. It is exothermic process.
5. It is exothermic process.
6. It is endothermic process.

9. On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.

1. Write a balanced chemical equation of the reaction involved
2. What other name can be given to this precipitation reaction?
3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

1. BaCl2(aq) + Na2SO3(aq) --------> BasO3(s) + 2naCl

10.You are provided with two containers made up of (A) copper and (B) aluminium. You are also provided with solutions of (a) dilute HCl (b) dilute HNO3(c) ZnCl2 and (d) H20. In which of the above containers these solutions can be kept?

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