NCERT solution of class for class 10th // Science // Chapter 1 - Chemical reaction and equation

 NCERT solutions > class 10th > Science - Chapter 1. 

NCERT solution of class for class 10th // Science  // Chapter 1 - Chemical reaction and equation


Chapter 1 - Chemical reaction and equation

        Page no. 6 

Q1. Why should a magnesium ribbon be cleaned before burning in air?

Ans- A magnesium ribbon be cleaned before burning in air  to remove all the unwanted impurities  on it and only pure magnesium can burn.

Q2. 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 

    

Q3. Write a balanced chemical equation with state symbols for the following reactions.

i ) Solution 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 - 

                            Page no . 10 

Q1. 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 in ( i ) above with water.

Ans -  

                                Page no . 13. 

Q1. 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 then it colour becomes brownish due to displacement reaction as shown in below 

CuSO4 + Fe -------- FeSO4 + Cu

Q2. Identify the substance that are oxidized and the substances that are reduced in following reactions. 

i) 4Na (s) + O2 ( g) ______2Na2 O

ii) CuO( s)  + H2 ( g)______Cu (s)+  H2O( l)

Ans i)  Sodium is oxidized and oxygen is reduced 

ii) copper oxide is reduced into copper while hydrogen get oxides into water

                     Exercise 

Q1. Which of the statements about the reaction below are incorrect.

2PbO(s) + C (s)_____ 2Pb( s ) + CO2 (g).

a) lead getting reduced

b) carbon dioxide is getting oxidized 

c) carbon is getting oxidized

 d) lead oxide is getting reduced.

i) A and B  

ii) A and C 

iii) A , B and C .

iv)  all 

Q2. Fe2O3 + 2Al _____  Al2O3 + 2 Fe 

The above reaction is an example of a 

 a) combination reaction  

b) double displacement reaction  

c) decomposition reaction  

d) displacement reaction 

Q3. 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.

Q4. What is balanced chemical equation why should chemical equation be balanced.

Ans- The balance chemical equation is that type of equation in which the number of elements in reactant is equal to the number of elements in product that is the number of each element before and after reaction should be same the chemical reactions will be balanced with respect to mass and charge on it because mass and charge neither be created nor be destroyed

 eg-  Zn + H2SO4 ______ ZnSO4 + H2

Q5. 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 sulphur dioxide.

c) Barium chloride reacts with Aluminium sulphate to give aluminium chloride and precipitate of barium sulphate.

d) Potassium metals react with water to give potassium hydroxide and hydrogen gas 

Ans - 


Q6 . 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+2 H2O   

Nitric acid +  Calcium Hydroxide___ Calcium Nitrate+ water        

b) 2NaOH  + H2SO4 _______ Na2SO4+ 2H2O

sodium Hydroxide + Sulphuric acid _____Sodium Sulphate + Water 

c) NaCl + AgNO3   _______  AgCl + NaNO3

Sodium Chloride + Silver Nitrate ____ Silver Chloride + Sodium nitrate 

d) Bacl2+ H2SO4 ______BaSO4 + 2HCl

Barium Chloride + Sulphuric acid ___ Barium Sulphate + Hydrochloric acid 

_                 

Q7 . 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- 

Q8. Write the balanced chemical equation for the following and identify the type of the reaction in each case.

a) Potassium bromide (aq) + Barium iodide (aq)____ Potassium iodide (aq)+ Barium bromide(g) 

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 - 


Q9 . What does one mean by exothermic and endothermic reaction give examples?

Ans- Exothermic reaction 

Reaction in which heat is given out along with the products are called exothermic reaction

Eg - Burning of magnesium ribbon 

2Mg. + O2 ____ 2MgO + heat 

Endothermic reaction 

The reaction in which energy is absorbed in the form of heat are called endothermic reaction.

Eg. - Photosynthesis

6CO2  + 12H2O ___heat____C6H12O6 + 6 H2O + 6 O2 

Q10. Why is respiration considered an exothermic reaction explain?

Ans- In the process of respiration the complex food molecules that is carbohydrate are oxidized or breaking down into simple food molecules like glucose during this process the energy is liberated so respiration is called exothermic reaction.

C6H12O6 + 6 H2O + 6 O2 ______6CO2  + 12H2O 

Q11  why are decomposition reaction called opposite of combination reaction write equation for these reactions.?

Ans- In a decomposition reaction a single reactant breaks down to give simple product

 CO2______C + O2 

But in a combination reaction two or more react and combined together to form a single product..

C + O2 _____ CO2

Q12. Write one equation each for the decomposition reaction where energy is supplied in the form of heat light or electricity? 

Ans-

 Heat   -  CaCo3______  Cao + CO2

Light  - 2AgCl  ___  2Ag + Cl2

Electricity -   2H2O ___ 2H2 + O2

Q13. What is the difference between displacement and double displacement reaction write equations for these reactions? 

Ans- In a displacement reaction a more reactive element displays that is reactive element and form its compound .

Mg + 2HCl _____ MgCl2 + H2              Displacement Reaction 

 but in double displacement reaction two compounds  combine by an exchange of ions to form the new compounds.

2KBr     + BaI2 ______2KI + BaBr2     Double Displacement

Q14. In the refining of silver the recovery of silver from silver nitrate solution involved displacement by copper metal write down the reaction involved? 

Ans- The reaction is involved in the refining of silver and the recovery of silver from the silver nitrate solution is 

2AgNO3 (aq) + Cu (s)_____ Cu( NO3)2 ( aq) + 2Ag (s)

Q15. What do you mean by that precipitation reaction explain by giving example? 

Ans- The reaction in which the formation of an insoluble solid mass called precipitate is known as precipitation reaction example when silver nitrate is added to an aqueous solution of sodium chloride a white precipitate of silver chloride is formed 

AgNO3( aq  )+ NaCl(aq)_____ AgCl  (s)+ NaNO3 (aq)


Q16. Explain the following in terms of gain or loss of oxygen with two examples each 

a) oxidation

 b) reduction 

Ans- oxidation is a process in which a substance gain oxygen

eg - 4Na+ O2 ____ 2Na2O

Reduction it is a process in which the substance loses oxygen

 eg -  2KClO3  _____ 2KCl + 3O2

Q17. 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 a copper and the black coloured compound is copper oxide 

2Cu + O2 ____ 2CuO     copper oxide

Q18. Why do we apply paint on iron articles? 

Ans- We apply paint on iron articles because it can be prevented from corrosion pen does not allow the atmospheric Oxygen and water to come in contact with the surface of iron 


Q19. Oil and fat containing food items are flushed with nitrogen why? 

Ans- Oil and fat present in the food atoms get oxidized and become rancid in presence of the atmospheric oxygen but such reaction is prevented in presence of nitrogen because nitrogen is unreactive gas as compared to the oxygen therefore packed food atom like potato chips are packed with nitrogen gas to prevent them from rancidity

Q20. Explain the following terms with one example each 

a) corrosion  

b) rancidity 

Ans- a) corrosion 

Corrosion is the phenomenon due to which the metals are slowly  eaten away by the reaction of air ,water and chemicals present in the atmosphere is called corrosion .The corrosion of iron is called rusting

b) Rancidity 

It is a process of slow  oxidation of oils and fats present in the food materials resulting in the change of smell and taste in them








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