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Thursday, June 7, 2018

MOST IMPORTANT QUESTIONS FOR CBSE CLASS 10 SCIENCE - CHEMICAL REACTIONS AND EQUATIONS


IMPORTANT QUESTIONS FOR CLASS 10 SCIENCE - CHEMICAL REACTIONS AND EQUATIONS

Class 10 science Chemical Reactions and Equations Important Questions



Chemical Reactions and Equations is the first chapter of CBSE Class 10 Science.In this chapter you are going to study about Chemical Reactions, writing of balanced chemical equations, Types of Chemical Reactions, Corrosion and Rancidity. This chapter has 5- 6 marks weightage in Board Exams. Here we are going to provide you the most Important Questions of this Chapter for Board Exams which are prepared by Experts.

Important Questions for Chemical Reactions and Equations from Previous Years CBSE Board Examinations


Very short questions (1 mark)

1. Write a chemical equation of double displacement reaction.

2. Why is respiration considered an exothermic reaction ?

3. Identify the chemical change: melting of ice or conversion of milk into curd.

4. Why do copper vessel lose shine when exposed to air ?

5. What changes do you observe in the iron nails and colour of copper sulphate solution, if iron nails are dipped in CuSO4 solution for 15 minutes ?

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

7. Potato chips manufacturers fill the packet of chips with nitrogen gas. Why?

8. Name the type of reaction:  N2 + 3H2 → 2NH3 

9. What happens when milk is left open at room temperature during summers?

10. Why does apple pieces become reddish brown if kept in air for a long time?

11. What happens when quick lime is added to water ?

Short type questions (2 marks)

1. Define combination reaction. Give one example of combination reaction which is exothermic in nature.

2. What is decomposition reaction ? Explain with the help of an example.

3. Name and state the law which is kept in mind when we balance a chemical equation.

4. Give one example of each :
(a) Chemical reaction showing evolution of gas.
(b) Change in substance’s colour during a chemical reaction.

5. What is rancidity ? Write two ways by which it can be prevented.

6. What are two conditions which promotes corrosion ?

7. A small amount of ferrous sulphate is heated in hard glass tube.
(a) write the chemical equation.
(b) what type of reaction is taking place.

8. What happens when Zn strip is dipped in CuSO4 solution ?

9. What happens when dilute HCl is added to iron fillings ?

Short type questions (3 marks)

1. In electrolysis of water :
(a) Name the gas collected at cathode and anode.
(b) Why is volume of one gas collected at one electrode is double of another ?
(c) Why are few drops of dil. H2SO4 added to water ?

2. Give Reasons :
(a) white silver chloride turns grey in sunlight.
(b) brown coloured copper powder on heating in air turns into black coloured substance.

3. A metal salt mx when exposed to light splits up to form metal m and gas x2. Metal m is used to make ornaments whereas gas x2 is used in making bleaching powder. The salt mx is used in black & white photography.
(a) identify the metal m and gas x2
(b) identify mx
(c) write down the chemical reaction when salt mx is exposed to sunlight.

4. A metal strip ‘x’ is dipped in blue coloured salt solution ySO4. After some time a layer of metal ‘y’ is formed on metal strip ‘x’. Metal ‘x’ is used in galvanization whereas metal ‘y’ is used for making electric wires.
(a) what could be metal ‘x’ and ‘y’ ?
(b) name the metal salt ySO4.
(c) what type of chemical reaction takes place between x and ySO4? Write the balanced chemical equation.

5. A white salt on heating decomposes to give brown fumes and a residue is left behind.
(a) Name the salt.
(b) Write the balanced chemical equation.

6. A zinc plate was put in a solution of copper sulphate kept in glass containe. It was found that blue colour of the solution gets fader and fader with the passage of time. After few days, when zinc plate was takenfrom the solution a number of holes were observed on it.
(a) State the reason for changes observed on the zinc plate.
(b) write the chemical equation for the reaction involved.


Long type questions (5 marks)

1. White wash was being done at Vikas’s house. Vikas saw that the painter added quick lime to drum having water. Vikas touched outer surface of drum, it is unbelievably hot.
(a) write the chemical equation for above reaction.
(b) what type of reaction is it ?

2. What types of reactions are represented by following :
(a) CaCO3 → CaO + CO2
(b) 2Ca + O2 → 2CaO
(c) Pb + CuCl2 → PbCl2 + Cu
(d) 2FeSO4 → Fe2O3 + SO2 + SO3
(e) Na2SO4 + BaCl2 → BaCl2 + 2NaCl

3. Balance the following equations :
(a) H2 + O2 → H2O
(b) MnO2 + HCl → MnCl2 + H2O + Cl2
(c) Pb(NO3) → PbO + NO2 + O2
(d) AgNO3 + NaCl → AgCl + NaNO3
(e) Ca(OH)2 + HNO3 → Ca(NO3)2 + H2O

4. Write down the balanced chemical equation for the following :
(a) silver chloride is decomposed in presence of sunlight to give silver and chlorine gas.
(b) calcium oxide reacts with water to give lime water.
(c) sodium hydroxide reacts with hydrochloric acid to give sodium chloride and water.
(d) dil. hydrochloric acid is added to copper oxide to give green coloured copper chloride and water.
(e) solution of barium chloride and sodium sulphate in water reacts to give insoluble barium sulphate and solution of sodium chloride.



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