CHEMICAL REACTIONS AND EQUATIONS – 3 Mark Questions

Q1. State one example each along-with the chemical equation characterised by the  following:

(i)  Change in state  

(ii) Evolution of gas

(iii) Change in temperature             

Q2. Balance the following chemical equations along with the symbols of physical states of all the reactants and the products:-

(i) Pb3O4 +HNO3 → Pb(NO3)2 + PbO2 +H2O

(ii)  C2H5OH + O2 → CO2  + H2O + Heat

(iii)  Pb3O4  + HCl→ PbCl2 + Cl2 + H2O

Q3. Study the reactions given and indicate which of the following chemical reactions will occur with suitable reason for each.

(i)  Zn(s) + CuSO4 (aq) → ZnSO4 (aq) + Cu(s)

(ii)  Fe(s) + ZnSO4(aq) → FeSO4 (aq) + Zn(s)

(iii)  Zn(s)  + FeSO4 (aq) → ZnSO4 (aq) + Fe(s)

Q4. What is a Redox reaction? Identify  the substances that  are  oxidised  and  the substances that  are reduced  in  the following  reactions:

(i) Fe2O3 +2Al → Al2O3 +2Fe

(ii) 2PbO+ C → 2Pb     + CO2   

Q5.  On heating blue coloured powder of Copper  (II)  Nitrate in a boiling tube,  Copper Oxide (black), Oxygen gas and a brown gas X are formed.

(i) Write a balanced chemical equation of the reaction.             ,

(ii)  Identify the brown gas X evolved.

(iii)   Identify the type of reaction.

(iv)  What could be the pH range of the aqueous solution of the gas X?

Q6.         (a) Mention the four type of information given by an equation.

               (b) State the law of conservation of mass as applicable in a chemical reaction.

Q8. Give reasons:

(i) All decomposition reactions are endothermic reactions.

(ii) Colour of Copper Sulphate solution changes when an iron nail is dipped in it.

(iii) Respiration is an exothermic reaction.

Q9. Write the chemical equation when:

(i) Dilute hydrochloric acid is added to solid Sodium Carbonate.

(ii) Quicklime is treated with Water.

(iii) Sodium chloride solution is added to Lead Nitrate solution.

Q10. 2g of ferrous sulphate crystals are heated in a boiling tube. Answer the following

(i) Write the colour of Ferrous Sulphate crystals both before heating and after heating.

(ii) Name the gases produced during heating.

(iii) Write the chemical equation for the reaction.

Q11. Identify the colour and chemical name of the substance of coating in silver, copper and iron when they are exposed to air.

Q12. Write an example  in each of the following case to support that :

(i) Corrosion of some metals is an advantage.

(ii) Corrosion of a metal is a serious problem.

Q13. Name the salts that are used in black and white photography.   Write the reactions when they are exposed to light. Define the type of chemical reaction taking place.

Q14. What information do we get from a balanced chemical equation?

Q15.  In a container, solid calcium oxide was taken and water was added slowly to it.

(a) State the two observations made in the experiment.

(b) Write the name and chemical formula of the product formed

Q16. Give reasons:

(a) Magnesium ribbon should be cleaned before burning in air.

(b) Photosynthesis is considered as an endothermic reaction.

(c) Combustion reaction is an oxidation reaction.

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