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Lesson-Based Assessment (LBA) – Science| Chemical Reactions and Equations (SSLC / Class 10)

  • Oct 28, 2025
  • 9 min read

Lesson-Based Assessment (LBA) – Science| Chemical Reactions and Equations (SSLC / Class 10)
Part A: Multiple Choice Questions (1 Mark Each)

  1. An example for a chemical change

    1. Dissolving salt in water 

    2. Tearing of paper 

    3. Rusting of iron ✅ 

    4. Boiling of water

  2. This is not a property of a chemical reaction:

    1. Change in colour 

    2. Release of heat 

    3. Change in shape ✅ 

    4. Release of gas

  3. Fe₂O₃ + 2Al ....................................Al₂O₃ + 2Fe This is an example of

    1. Combination reaction

    2. Decomposition reaction

    3. Displacement reaction ✅

    4. Double displacement reaction

  4. The group of reactant  among the following which react with each other to exchange ions and form a precipitate is

    1. Bacl2 and  Na2SO4 ✅

    2. Al2O3 and HCl     

    3. NaOH and H2SO4     

    4. Na2O and CO2

  5. Electrolysis of water results in the evolution of hydrogen and oxygen gases

    1. Double displacement reaction 

    2. Exothermic reaction     

    3. Displacement reaction

    4. Decomposition reaction       

  6. Reaction in which reactants exchange their ions

    1. Double displacement reaction 

    2. Exothermic reaction     

    3. Displacement reaction

    4. Decomposition reaction  

  7. In CuO + H₂ ..........................Cu + H₂O, oxidation and reduction occur in

    1. Cuo + H2

    2. H2+ Cuo  

    3. Cu + H2O  

    4. H2O + Cu

  8. Silver nitrate dance into grey colour in the presence of Sunlight because

    1. Silver chloride decomposes to form silver

    2. Silver chloride decomposes to form chlorine

    3. Silver chloride undergoes oxidation

    4. Silver chloride undergo reduction

  9. The ratio of hydrogen to oxygen gases released in electrolysis of water is:

    1. Hydrogen :Oxygen :: 1:2          

    2. Oxygen : Hydrogen  ::  2 : 3        

    3. Hydrogen : Oxygen : : 2:1       

    4. Oxygen : Hydrogen ::  3:2

  10. The conversion of vegetable waste into compost is an example for

    1. Reduction reaction       

    2. Exothermic reaction       

    3. Endothermic reaction        

    4. Redox reaction

  11. The gas released at the cathode in the electrolysis of water is

    1. Oxygen    

    2. Hydrogen     

    3. Chlorine      

    4. Nitrogen

  12. Identify the chemical equation in which the chemical reaction takes place in the following

    1. FeSO4 + Pb ------ PbSO4 + Fe     

    2. ZnSo4 +Fe------ FeSO4 + Xn

    3. 2 AgNo3 + Cu -------- (CuNo3)2 + Ag     

    4. PbCl2 + Cu------  CuCl2 + Pb

  13. When dilute hydrochloric acid is added to iron fillings

    1. hydrogen gas and iron chloride are produced

    2. chlorine gas and ferric Hydroxide are produced

    3. no reaction takes place       

    4. ferrous salt and water produced

  14. The metal that displaces copper from copper sulphat

    1. Gold    

    2. silver    

    3. copper  

    4. iron

  15. Ferrous sulphate crystal lose their green colour when heated because this compound

    1. Breakdown into simpler compounds

    2. Losses water molecules 

    3. Releases Sulphur Dioxide gas

    4. Produces brown smoke

  16. Chip manufacture flush bags of chips with Nitrogen gas because

    1. To prevent corrosion    

    2. To prevent oxidation      

    3. To cause corrosion   

    4. To prevent reduction


Part B: Short Answer Questions (1 Mark Each)

  1. What is a chemical reaction?

    A process in which one or more substances (reactants) are converted into new substances (products).

  2. What is a chemical equation?

    A symbolic representation of a chemical reaction using symbols and formulae.

  3. Why is a magnesium ribbon cleaned before burning?

    To remove the oxide layer so that magnesium burns easily in air.

  4. Why should chemical equations be balanced?

    To obey the Law of Conservation of Mass.

  5. Why are decomposition of vegetable matter and respiration exothermic reactions?

    Because heat is evolved in both cases.

  6. What is a precipitation reaction? Give an example.

    A reaction in which an insoluble solid (precipitate) forms.Example: BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl

  7. What is corrosion?

    Gradual deterioration of metals due to air, moisture, or acids.

  8. Why are chip packets flushed with nitrogen?

    Nitrogen prevents oxidation and spoilage of food.

  9. Why should iron articles be painted?

    To prevent rusting.

  10. What is rancidity?

    Oxidation of food that changes its smell and taste.

  11. Methods to prevent rancidity:

    1. Store in airtight containers

    2. Refrigerate-Keep Food in Refrigerator

    3. Oil food flushed with nitrogen

  12. Identify oxidized and reduced substances:Zn + CO → ZnO + C

    1. Oxidized: Zn 

    2. Reduced: CO

  13. When sodium sulphate solution is added to Barium Chloride solution a white precipitate of Barium sulphate is formed which are the ions responsible for this precipitate formation?

    1. Barium ( Ba++)

    2. Sulphate (SO4 --)

  14. Product formed when CaO reacts with water

    Calcium hydroxide (slaked lime)

  15. The magnesium ribbon burns with a dazzling white flame in air and changes into magnesium oxide identify the type of reaction

    Combination reaction


Part C: Two-Mark Questions

  1. List out the observation that help us to determine that a chemical reaction has taken place

    Chemical reaction take place

    1. Change in state

    2. Change in colour

    3. Evolution of a gas

    4. Change in temperature

  2. What is a combination reaction? Give an example

    A reaction in which 2 or more reaction combined to give a singke product is caled combination reaction Mg + O2--------- MgO

  3. What is a decomposition reaction give an example

    A reaction in which single reactant breaks up in to  2 or more product is called  decomposition reactiom FeSO4 -------------------- Fe2O3 + SO2 + SO3

  4. What is a displacement reaction give an example

    More reactive element diaplaces the least one is called displacement reaction.

    2Pb(No3)2-----------2 PbO + 4 NO2 + O2

  5. Why does an iron nail change its colour when immersed in copper sulphate solution write the chemical equation for this reaction

    Because it is a displacement reaction here iron displaces the copper from copper sulphate solution Fe + CuSO4 ---------- FeSO4 + Cu

  6. FeSO4 + Cu ------- CuSO4  + Fe Is it possible for the above chemical reaction to take place justify your answer

    It is not possible. Because copper is less reactive than iron

  7. What is a double displacement reaction give an example

    Exchange of Ions from the reactant side is called double displacement or double decomposition reaction Nacl + AgNO3 --------- AgCl + NaNO3

  8. Which colour precipitation is formed when the lead nitrate solution is mixed with potassium iodide solution?name the precipitate and identify the type of chemical reaction?

    Pb( NO3)2 + 2 KI ------------ PbI2 + 2 KNO3 . Yellow colour precipitate, Precipitate name is Lead iodide, Double decomposition reaction

  9. Name the brown fumes liberated when Lead Nitrate is heated write the balanced chemical equation for this reaction

    Nitrogen dioxide ( NO2)  2 Pb(NO3)2   ------------ 2 PbO + 4 NO2 + O2

  10. What are endothermic and exothermic reaction? Give an example for each

    Endothermic reaction is a chemical reaction that consumes heat to form products . Ex: N2 + O2 ---------2 NO

    Exothermic reaction is a reaction in which energy is evolved. Ex: adding water to calcium oxide CaO + H2O ------- Ca( OH)2  + heat

  11. When calcium carbonate is heated calcium oxide and carbon dioxide are produced. write the balanced chemical equation for this reaction and state the type of chemical reaction

    Caco3----------- CaO + CO2.  It is  thermal decomposition reaction

  12. What is Redox reaction? Give example

    A chemical reaction in which both oxidation reduction takes place simultaneously

    ZnS + Cu ------- Zn + CuS

  13. The chemical reaction that takes place between sodium sulphate solution and Barium Chloride solution is called double displacement reaction. Why? Write a balance chemical equation for this reaction

    Na2SO4 + BaCl2 --------- BaSO4 + 2 NaCl . It is called double displacement reaction because here exchange of ions in the reactant side will take place

  14. Which is the type of chemical reaction where the quicklime is obtained from limestone calcium carbonate. Write the chemical equation for this reaction

    It is a thermal decomposition reaction. CaCO3 ------ CaO + CO2

  15. Mention any two measures to prevent corrosion ( rusting of iron)

    Preventive measures are  : painting,galvanizing,anodizing, chrome plating, oiling etc

  16. Shiny brown coloured element X on heating in air becomes a black colour compound  Y then

    1. A. Name the element X: Copper

    2. Name the compound Y: CuO

  17. The given equation represent reaction of copper sulphate with an element  X

    CuSO4 + X -----------Cu + Y

    1. Which element is represented by X among Fe and Ag? Justify your answer:  X is Fe because it displace copper fast than Ag

    2. Write the molecular formula of the compound  Y: B-----FeSO4

  18. Draw a diagram of the Apparatus used in electrolysis of water and label the following parts

    1. Graphite rod

    2. Oxygen


Part D: Three Mark Questions

  1. To a solution of 5 ml of sodium sulphate solution if the same amount of Barium Chloride is added then

    1. Name the white precipitate formed

    2. Name the ions responsible for the formation of white precipitate

    3. Mention the type of chemical reaction

    Answer :

    1. BaSO4 Barium sulphate

    2. Ions are barium and sulphate

    3. Double displacement

  2. Strips of zinc,  iron, magnesium  and copper are taken in test tube A, B, C, D respectively equal amount of ferrous sulphate solution added to these test tubes in each of these test tube does the chemical reaction takes place why? Write the chemical equation for the reaction taking place here

    Chemical reaction occur in test tube A and C, because zinc and magnesium are more reactive than iron or zinc and magnesium are found about Iron in the reactivity series of metal.zinc + ferrous sulphate -------zinc sulphate + iron

    or

    Zn + FeSO4 ------ ZnSO4  + Fe magnesium + ferrous sulphate --------- Magnesium Sulphate  + iron

    or

    Mg + FeSO4 --------- MgSO4 + Fe

  3. Explain with an example each for the decomposition reaction that takes place when energy is supplied in the form of heat light and electricity

    The Three Types of decomposition reactions are

    • Thermal decomposition reaction: Rreaction in which decomposition of a reaction takes place by heating. Ex: CaCO3------- CaO + CO2

    • Electrolytic decomposition reaction: Reaction takes place by passing electricity.  Ex : 2H2O -------- 2 H2 + O2

    • Light decomposition reaction : Decomposition reaction in the presence of light.Ex: 2 AgCl --------- 2Ag + Cl2

  4. Name the salts that are used in black and white photography write the equation for the reaction when they are exposed to sunlight

    Silver Chloride and Silver Bromide

    AgCl-------- Ag + Cl2

    AgBr --------- Ag + Br2

  5. A solution of substance Z is used for whitewashing

    1. Name the substance Z: Calcium oxide ( quicklime )

    2. Write its molecular formula: CaO

    3. Write a balanced chemical equation when Z is reacts with water: CaO + H2O ------Ca( OH)2

  6. What type of chemical reaction takes place when an iron nail is immersed in a copper sulphate solution? Why? Write balance chemical equation for this chemical reaction

    Displacement reaction, Because iron is more reactive than copper. Fe + CuSO4---------- FeSO4 + Cu

  7. The reaction of Barium Chloride with Aluminium Sulphate solution is an example for which type of chemical reaction? Why? Write the balance chemical equation for this reaction

    Double displacement reaction,Exchange of iron takes place in reactant side.3 BaCl2 + Al2 ( SO4)3 ---------- 3 BaSO4 + 2 AlCl3

  8. Write balanced chemical equation for the following chemical reactions

    1. Calcium carbonate-------------- calcium oxide + carbon dioxide

    2. Hydrogen + chlorine ------------ hydrogen chloride

    3. Magnesium + hydrochloric acid --------- magnesium chloride + hydrogen

    Answer:

    1. CaCO3  ------------ CaO + CO2

    2. H2 + Cl2  ----- 2HCl

    3. Mg + 2Hcl   ------------  MgCl2 + H2

  9. Balance the following chemical equations

    1. H2 + O 2 -------- H2O

    2. Na2CO3 + HCl -------- NaCl + H2O + CO 2

    3. N2 + H2 ------- NH3

    Answer:

    1. 2H2 +  O2 ---------- 2H2O

    2. Na2Co3 + 2HCl ----------2 NaCl + H2O + CO2

    3. N2 + 3H2 ------- 2NH3

  10. Write balanced equation for the following chemical reactions

    1. Quickline has reacted with water

    2. Zinc flakes were added to copper sulphate solution

    3. sodium chloride solution is added to Silver Nitrate solution

    Answer

    1. CaO + H2 O -------- Ca ( OH)2   + heat

    2. Zn + CuSO4 ------ ZnSO4 + Cu

    3. NaCl + AgNO3 --------- AgCl + NaNO3

  11. Translate the following statements into balanced chemical equation

    1. Hydrogen sulphide gas burns in air to give water and sulphur dioxide

    2. Barium Chloride reacts with Aluminium Sulphate to give aluminium Chloride and Barium sulphate

    3. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas

    Answer

    1. 3H2S + 3O2------ 3H2O + 3SO2

    2. 3BaCl2 + Al2( SO4)3 --------- 3BaSO4 + 2AlCl3

    3. 2K+ 2H2O ------ 2KOH + H2

  12. Write the balanced equation for the following chemical reaction

    1. Combustion of natural gas: CH4 + 2O 2 ------- CO2  + 2H2O

    2. Reaction of potassium metal with water: 2K+ 2H2O ------2 KOH + H2

    3. Reaction of iron with copper sulphate:Fe + CuSO4---------- FeSO4 + Cu

  13. Explain the following with chemical equation

    1. Oxidation: Addition of oxygen or removal of hydrogen is called oxidation.Ex: CuO + H2 -------- Cu + H2O. Here  H2 oxidises to H2O

    2. Reduction:Removal of oxygen or addition of hydrogen is called reduction. Ex: CuO + H2 -------- Cu + H2O. Here CuO reduces to Cu


Part E: Four Mark Questions

  1. Lead Nitrate is mixed with potassium iodide solution answer the following questions related to the above chemical reaction

    1. Write the balance equation for this reaction:: Pb(NO3)2  + 2 KI  --------  PbI2 + 2 KNO3

    2. Name the precipitate formed in this reaction: Lead iodide (PbI2)

    3. Name the colour of the precipitate: Yellow colour

    4. What type of chemical reaction this is: Double displacement or precipitation reaction

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

    1. Hydrogen + oxygen ------- water: 2 H2 + O2 ----- 2 H2O.Combination reaction

    2. Zinc sulphate + copper --------- copper sulphate + zinc: ZnSO4 + Cu -------- CuSO4 + Zn.  Displacement reaction

    3. Zinc carbonate --------- zinc oxide  + carbon dioxide: ZnCO3-------- ZnO + CO2.Decomposition reaction

    4. Sodium chloride +  silver nitrate -------------  silver chloride  + sodium nitrate: NaCl + AgNO3 ------- AgCl + NaNO3.Double displacement reaction

  3. Give reasons

    1. Objects made of copper lose their luster when exposed to air: Because copper is a metal when it is reacts with carbon dioxide in air to form copper carbonate hence it loses its luster

    2. .An iron nail place it in a solution of copper sulphate slowly turns Brown: due to displacement iron is more reactive than copper it changes its colour

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