Chemical Reactions and Equations: Important Questions and Explanation

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Anjali Mishra

Content Writer-SME | Updated On - Oct 3, 2024

CBSE Class 10th Science Exam consists of 4 important question sections. Section A consists of one mark questions. These questions include MCQs, very short answer type questions. Short answer type questions, long answer type questions and assertion-reason type questions are included in Sections B and C which carry questions of 3 marks and 5 marks respectively.

This article provides the reader with an exhaustive list of each type of questions from the scince chapter Chemical Reactions and equations along with their model answers. The HOTS questions and their answers from the chapter of Chemical Reactions and Equations can be downloaded from the pdf below:

Read Also: Chemical Reactions 


Multiple Choice Type Questions [1 Mark]

Question: Why is the magnesium ribbon rubbed with sandpaper before being burnt in the air?

(a) For removing the moisture from the surface of the ribbon.

(b) For removing the magnesium carbonate layer from the surface of the ribbon

(c) For making the surface of the ribbon shinier

(d) For removing the layer of magnesium oxide from the surface of the ribbon

Ans: (d) For removing the layer of magnesium oxide from the surface of the ribbon.

Click here for the explanation

Explanation: Magnesium (Mg) being a reactive element undergoes oxidation reaction in presence of air. This results into the formation of Magnesium Oxide (MgO) which slows down the rate of burning. Therefore, magnesium ribbon is rubbed with sandpaper before being burnt in the air. 

Question: The reaction H2+Cl→ 2HCl represents:

(a) Reduction

(b) Oxidation

(c) Decomposition

(d) Combination

Ans: (d) Combination

Click here for the explanation

Explanation: The reaction in which two or more reactants participates in the formation of one single product is called combination reaction. The reaction H2+Cl→ 2HCl is a classical example of combination reaction in chemistry

  • The combination reaction is expressed by the general formula: A+B→C.
  • Other examples of combination reactions include the formation of carbon dioxide by mixing carbon and oxygen in certain proportions.

Question: Name the gas that is helpful in the storage of fat and oil-containing foods for a longer period: 

(a) Carbon dioxide

(b) Oxygen

(c) Nitrogen

(d) Neon

Ans: (c) Nitrogen

Click here for the explanation

Explanation: Nitrogen is an important gas present in the earth's crust that prevents food products from rancid smell. Thus, nitrogen helps in storing foods containing fats and oils for a longer period of time.

Question: The substance which can oxidize itself and reduce others is:

(a) Oxidising and Reducing Agent

(b) Oxidising agent

(c) Reducing agent

(d) None of these

Ans: (c) Reducing agent

Click here for the explanation

Explanation: A reducing agent reduces electrons by oxidizing itself while the oxidizing agent gains electrons.. Here, in the redox reaction given below Sodium (Na) acts as reducing agent as the positive charge denotes the loss or donate of electrons. Also, Chlorine (Cl) acts as oxidizing agent due to the gain of electrons. Furthermore, chlorine (Cl) acts as an oxidizing agent due to the gain of electrons.

2Na(s) + Cl(g)→2Na+ + Cl-(s)

Question: Heat evolves in which type of reaction?

(a) During Displacement Reaction

(b) During Endothermic Reaction

(c) During Exothermic Reaction

(d) During Combination Reaction

Ans: (c) During Exothermic Reaction

Click here for the explanation

Explanation: The reaction in which heat is evolved is called exothermic reaction. The practical and real life examples of exothermic reaction are: 

  • Respiration
  • Burning of candle
  • Rusting of iron
  • Reaction of strong acid with water
  • Decomposition of vegetables by microbes.

Question: Copper displaces which metal from its salt solution:

(a) AgNO3

(b) FeSO4

(c) ZnSO4

(d) NiSO4

Ans: (a) AgNO3

Click here for the explanation

Explanation: In chemistry, displacement reaction occurs between a more reactive and less reactive element in which the more reactive element displaces the less reactive element. The reactivity of copper is higher than that of silver. Therefore, copper displaces silver metal or its compounds (AgNO3) from its salt solution.

Question: Chemical equations satisfies the law of:

(a) Conservation of motion

(b) Conservation of momentum

(c) Conservation of energy

(d) Conservation of mass

Ans: (d) Conservation of mass

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Explanation: All chemical reactions and equations of class 10 follow a universal principle of chemistry called conservation of mass. According to the principle of mass conservation, "total mass can neither be created nor destroyed in a chemical reaction.

Question: What’s the ratio in which hydrogen and oxygen are available in water by volume?

(a) 1:2

(b) 1:1

(c) 2:1

(d) 1:8

Ans: (c) 2:1

Click here for the explanation

Explanation: The chemical formula of water is written as H2O which is made up of two hydrogen and one oxygen atoms. Thus, the ratio of hydrogen and oxygen in water is 2:1. 

Question: Name the chemical reaction that takes place when electricity is passed through water.

(a) Displacement

(b) Combination

(c) Decomposition

(d) Double displacement

Ans: (c) Decomposition

Click here for the explanation

Explanation: The chemical reaction that occurs when electricity is passed through water is called electrolysis of water. This is a type of decomposition reaction. The chemical reaction and equation for electrolysis of water is given as follows:

2H2O→O+ 2H2 

Question: Pb + CuCl2 → PbCl2 + Cu

The above reaction is an example of:

(a) Combination reaction

(b) Double displacement reaction

(c) Decomposition reaction

(d) Displacement reaction

Ans: (d) Displacement reaction

Click here for the explanation

Explanation: Displacement reaction is a type of reaction in which a reactant that is more reactive displaces a less reactive element. Real life examples of displacement reactions are:

  • Rusting of iron
  • Formation of soap scum
  • Iron or metal extraction
  • Acid indigestion

Very Short Answer Type Questions [1 Mark]

Question: State the reason for the combustion of Liquefied Petroleum Gas (LPG) being a chemical change. 

Ans: Combustion of Liquefied Petroleum Gas (LPG) is a Chemical Change because it is an irreversible reaction which means the substances formed cannot be turned back into LPG. The new products Carbon Dioxide and Water Vapour are formed and a lot of heat is also produced during the reaction. 

Question: Identify the mistake and balance the following equation.

Mg + O →MgO 

Ans: Here, Oxygen should be in molecular form (O2) as oxygen exists as bimolecular gas 

2Mg + O→ 2MgO

Question: Potassium chlorate (KCIO3), after heated, results in oxygen and potassium chloride. State the balanced equation for this reaction. 

Ans: 2KClO3(s) → 2KCl(s) + 3O2(g)

2 molecules of Potassium chlorate (KClO3) on heating form 2 molecules of potassium chloride and 3 molecules of oxygen.

Question: After heating copper(II) nitrate, blue colored powder in a boiling tube, copper oxide (black), oxygen gas, and a brown gas 'X' is formed. Can you Identify the brown gas 'X'?

Ans: The equation of the reaction after balancing it is-

2Cu(NO3)2(S) → 2CuO(S) + 4NO2(g) + O2(g)

So, The "X" is nitrogen dioxide(brown).

Question : Write the chemical equation for : an aq. solution of ferrous sulphate reacting with an aq. solution of sodium hydroxide to form a ppt. of ferrous hydroxide and sodium sulphate remaining in solution.

Also, Balance the equation. 

Ans: FeSO4(aq) + 2NaOH(aq) → Fe(OH)2(s) + Na2SO4(aq)

Question: Balance this chemical reaction: 

Pb(NO3)2 → PbO + NO2 + O2

Ans: 2Pb(NO3)2 → 2PBO + 4NO2 + O2

Question: Give an example of a combination exothermic reaction.

Ans: When quicklime(CaO) reacts with water, slaked lime [Ca(OH)2] is formed. A heavy amount of heat is released during the reaction. So, this reaction is exothermic.

CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat

Question: State the reason: 

Copper powder that is heated becomes black when air is passed on it.

Ans: When air is passed on brown colored copper powder, it turns into black color due to the formation of black Copper Oxide. 

2Cu(s) + O2(g) → 2CuO(s)

Question: Can you identify the differences between these two types of reactions? 

AgNO3 + HCl → AgCl + HNO3 

Mg + 2HCl → MgCl2 + H2 

Ans: The first one is Double Displacement Reaction whereas the second one is displacement reaction. 

Question: State the reason behind keeping hydrogen peroxide in colored bottles.

Ans: Hydrogen peroxide is a very reactive chemical that can react with Light or heat to produce Water. It is highly unstable and slowly decomposes when kept in the presence of Light. So, to prevent this Hydrogen Peroxide is kept in colored bottles. 

Question: Observe these reactions: 

(i) Fe + CuSO4 → FeSO4 + Cu 

(ii) Cu + FeSO4 → CuSO4 + Fe 

Question: Which reactions can take place and why? 

Ans: The first reaction will take place because Fe (iron) is more reactive than Cu (copper), so it can displace Cu from its compound (CuSO4). On the other hand, copper (Cu) cannot displace iron (Fe), so the second reaction will not take place.

Question: Suggest one example of a reaction that is a double displacement reaction and also a precipitation reaction.

Ans: AgNO3(aq)+NaCl(aq)→AgCl(s)↓(ppt.)+NaNO3(aq)

Question: Digestion of food in our body is which type of reaction? 

Ans: Decomposition reaction takes place during the digestion of food in our body. 

Question: At the moment when the products are highly soluble or highly ionised, Can a double displacement reaction take place? 

Ans: No, Double displacement reaction cannot take place in this situation as it takes place only when there’s a formation of a slightly soluble salt after the reaction.

Question: Name the oxidising and reducing agent in this reaction: 2H2S + SO2 → 2H2O + 3S ↓ 

Ans: SO2 is the Oxidising Agent and 2H2S is the Reducing Agent.

Dowload :  Class 10th Science Sample paper 2021


Short Answer Type Questions [3 Marks] 

Question: Write the chemical equations for these and also balance them: 

  1. A Precipitate of lead sulphate and nitric acid is produced when Lead Nitrate and Sulphuric Acid react. 
  2. Magnesium being burnt in the availability of nitrogen and forming magnesium nitride. 
  3. To produce aluminium chloride and hydrogen gas, an Aluminium metal strip is added to hydrochloric acid.

Ans:

  1. Pb(NO3)2(aq) + H2SO4(aq) → PbSO4 (s) + 2HNO3 (aq)
  2. 3Mg(s) + N2(g) → Mg3N2(s)
  3. 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)

Question: State an example of thermal decomposition and photochemical decomposition reactions. Also, Write balanced equations for them.

Ans: Calcium carbonate decomposing to produce calcium oxide and carbon dioxide is an example of a Thermal Decomposition reaction. 

CaCO3(s) → CaO(s) + CO2(g)

When the silver chloride (AgCl) is kept in sunlight, it decomposes into silver and chlorine. It is a Photochemical Decomposition reaction. 

2AgCl(s) → 2Ag(s) + Cl2(g)

Question: Write the balanced chemical equations and also identify the type of reaction in the Following :

(i) Nitrogen gas reacts with hydrogen in the presence of a catalyst at 773 K temperature to form ammonia gas. 

(ii) Sodium hydroxide solution is reacted with acetic acid to produce sodium acetate and water. 

(iii) Ethene being burnt in the availability of oxygen to form carbon dioxide, water and releases heat and light. 

Ans: (i) N2 + 3H2 + Catalyst/773 K → 2NH3

It is a Combination Reaction. 

(ii) NaOH + CH3COOH → CH3COONa + H2

 It is a Double Displacement Reaction. 

(iii) C2H4 + 3O2 → 2CO2 + 2H2O + Heat + Light. 

It is a Redox reaction. 

Question: Name the type of chemical reaction taking place in the following equation:

(i) CaO + H2O → Ca(OH)2 

(ii) 3BaCl2 + Al2(SO4)3 → 2AICl3 + 3BaSO4 

(iii) 2FeSO4 → Fe2O3+ SO2 + SO3

Ans: (i) Combination reaction.

(ii) Double displacement reaction.

(iii) Decomposition reaction.

Question: Pen down the chemical equations and then balance the equations for: 

(i) Phosphorus Pentoxide being produced when Phosphorus is burnt in oxygen.

(ii) Aluminium metal replacing iron from ferric oxide, Fe2O3, producing aluminium oxide and iron. 

(iii) To produce carbon dioxide and sulphur dioxide, Carbon disulphide is burnt in the air. 

Ans: (i) P4 + 5O2 2P2O5

(ii) 2Al + Fe2O3 Al2O3+ 2Fe

(iii) CS2 + 3O2 CO2 + 2SO2

Question: Identify the oxidant in the following reactions. 

(i) Pb3O+ 8HCL → 3PbCl2 + Cl2 + 4H2

(ii) 2Mg + O2 → 2MgO 

(iii) CuSO4 + Zn → Cu + ZnSO4

(iv) V2O5 + 5Ca → 2V + 5CaO 

(v) 3Fe + 4H2O → Fe3O4 + 4H2 

(vi) CuO + H2 → Cu + H2

Ans: (i) Pb3O4 gets reduced to PbCl2 and oxidises HCl to Cl2

(ii) O2 is an Oxidant as it Oxidises Mg to MgO.

(iii) CuSO4 is an Oxidant as it oxidises Zn to ZnSO4.

(iv) V2O5 is an Oxidant as it oxidises Ca to CaO

(v) H2O is an Oxidant. Iron Metal is Oxidised. 

(vi) CuO is an Oxidant. CuO is reduced to Cu while H2 gets oxidised to H2O.

Question: Identify the type of reaction in these examples: 

(i) Na2SO4(ag) + BaCl2(aq) → BaSO4(s) + NaCl(ag) 

(ii) Fe(s) + CuSO4(aq) →FeSO4(aq) + Cu(s) 

(iii) 2H2(g) + O2(g) →2H2O(l) 

Ans: (i) Double Displacement Reaction

(ii) Displacement Reaction

(iii) Combination Reaction

Question: These observations were made when some metals were treated with dilute hydrochloric acid : 

(i) Silver Metal does not show any Change. 

(ii) The temperature of the reaction mixture increases when aluminium is being added. 

(iii) The reaction of sodium metal is seen to be highly explosive. 

(iv) Some bubbles of gas are noticed when lead (Pb) is reacted with the acid.

Explain these observations stating suitable reasons. 

Ans: (i) This happens because silver lies below hydrogen in the reactivity series and cannot displace hydrogen when reacted with acid.

(ii) The reaction of Aluminium with dilute HCl is exothermic, i.e. heat is evolved in the reaction. So, the temperature of the reaction mixture increases.

(iii) Sodium is a highly reactive metal. It reacts explosively with hydrochloric acid to form sodium chloride and hydrogen with the evolution of heat too. H2 Gas produced catches fire immediately. 

(iv) Lead lies just above the hydrogen in the activity series of metals. So, it is a little more reactive and displaces hydrogen from acid very slowly and to a small extent. Therefore, only bubbles of H2 are seen to evolve.

Pb(s) + 2HCl(Aq) → PbCl2 + H2(g)

Question: A White Compound X is produced accompanied by emission of light when A magnesium ribbon is burnt in oxygen. If we keep the burning ribbon in an atmosphere of nitrogen, it keeps on Burning and forms a compound Y. 

(i) Pen down the chemical formula of X and Y. 

(ii) Also show the balanced chemical equation when X is dissolved in water. 

Ans: (i) Magnesium ribbon burns in oxygen(O2) to form magnesium oxide (MgO). 

2Mg + O→ 2MgO

Therefore X is MgO.

Burning magnesium ribbon reacts with nitrogen(N2) to form magnesium nitride(Mg3N2).

3Mg + N→ Mg3N2

Therefore, Y is Mg3N2

(ii) If X is dissolved in water, it produces magnesium hydroxide.

MgO(s) + H2O(l) → Mg(OH)2(Aq.)

Question: (i) What do you notice in a test tube when a potassium iodide solution is added to a lead nitrate solution?

(ii) What type of reaction is this? 

(iii) Also write a balanced chemical equation.

Ans: (i) A precipitate of lead iodide (PbI2) Is formed that is Yellow.

(ii) Precipitation Reaction/Double displacement reaction.

(iii) Pb(NO3)2(aq.) + 2KI(aq.) → PbI2(s) + 2KNO3(aq.)


Long Answer Type Questions [5 Marks] 

Question: Observe the below Equation and then answer the questions

CuO + H2 → Cu + H2O

(i) Which Substance is getting oxidised. 

(ii) Which Substance is getting reduced. 

(ii) Which is the oxidising agent. 

(iv) Which is the reducing agent. 

(v) What type of reaction is this? 

Ans: (i) The substance getting oxidised is H2

(ii) The substance getting reduced is CuO. 

(iii) CuO is the oxidising agent. 

(iv) H2 is the reducing agent. 

(v)This is a redox reaction as oxidation and reduction is taking place.

Question:.You have: 

(a) Quick lime

(b) Cu powder

(c) Bacl2

(d) CuSO4 solution

(e) Ferrous sulphate crystal

(f) Iron Nails

Write at least 5 reactions that can take place from these substances

Ans: (i) Fe + CuSO4FeSO4 +Cu

(ii) CuSO4 + BaCl2BaSO4 + CuCl2

(iii) CaO+ FeSO4 CaSO4 + Fe2O3

(iv) BaCl2+CaOBaO+CaCl2

(v) BaCl2+FeSO4→BaSO4+FeCl2

Question: Give the Characteristic tests for the following gases: (i) H2 (ii) SO2 (iii) O2 (iv) CO2

Ans: (i) H2 gas produces a pop sound when a burning candle is brought near it.

(ii) When SO2 gas is passed through acidic potassium permanganate solution (purple), SO2 being a Strong Reducing Agent Changes it to colorless. 

2KMnO4+ 2H2O+ 5SO2 → K2SO4+ 2MnSO4+ 2H2SO4

(iii) When we bring a burning candle near the test tube that contains the reaction mixture. The intensity of the flame rises as oxygen(O2) supports burning.

(iv) When CO2 gas is passed through lime water, it turns milky because insoluble calcium carbonate is formed.

Ca(OH)2 + CO2 → CaCO3 + H2O

Question: Show through an experiment that hydrogen and oxygen are released when electric current is passed through water. 

Ans: 

Show through an experiment that hydrogen and oxygen are released when electric current is passed through water

(i) Take a plastic vessel and make two holes at the bottom. Set rubber stoppers and Insert carbon electrodes. Also, make a Connection to these electrodes with a 6-12 volt battery and a switch. 

(ii) Fill the vessel with water and immerse the electrodes. Also, add some drops of dilute sulphuric acid.

(iii) Take two graduated test tubes and fill them with water. Then put them in an inverted Position over the two carbon electrodes. 

(v) Switch on the current. 

(vi)Wait for some time and you will notice the bubbles at both electrodes. These bubbles displace water in the graduated tubes. 

(vii) Remove the test tubes when they are filled with gases. 

(viii) Test these gases by bringing a burning candle to the mouth of test tubes. When the candle is brought close to the mouth of one test tube, the intensity of flame rises and when it is brought close to the mouth of another test tube, the gas burns with a pop. Oxygen is the only common gas that increases the intensity of the flame and hydrogen gas burns with a pop.

Question: ‘Iron is more reactive than copper’. Justify the statement with the help of an experiment. 

Ans: A more reactive metal displaces the less reactive metal. With the help of the Reactivity Series of Metals, We can say that Iron is More reactive than Copper and Can displace Copper Sulphate from its Salts. 

(i) Take a solution of Copper Sulphate in a Test Tube.

(ii) Dip an iron nail in that Solution.

(iv)Notice the Reaction after some time.

You’ll notice that the reaction has occurred in iron nail and copper sulphate solution. The Initial Blue Color of the Solution turns to light green. Iron takes the sulphate away from copper. A brown coating can be seen on the iron nail. The color change is due to the formation of Iron Sulphate Solution which is light green. 

Copper sulphate + Iron → Iron sulphate + Copper

Now, We can say that more reactive metal i.e. iron has displaced less reactive metal i.e, Copper, from Copper Sulphate Solution. 

Question: Explain these terms with at least one example each.

  1. Corrosion
  2. Rancidity

Ans: Corrosion: It is the natural process in which metals are slowly transformed into undesirable substances by the action of water, air moisture, or chemicals. Rusting of iron is an example of corrosion where iron is eaten up by the action of air and moisture and a reddish-brown coating of iron oxide is formed.

2Fe+3H2O→Fe2O3+3H2

Rancidity: This is the process in which the substance containing oils and fats that are exposed to air gets oxidised and becomes rancid due to which their smell, taste, and color change. Change in smell and taste of butter due to exposure to air for a long time is an example of Rancidity. 

Question: Pen down the Chemical equation when zinc granules are treated with a dilute solution of HNO3, H2SO4, NaCl, HCl, and NaOH?

Ans: The reaction of Zn granules with

(i) Dilute HNO3 

4Zn(s) + 10HNO3(aq) → 4Zn(NO3)2(aq) + 5O2(l) + N2O(g)

(ii) Dilute H2SO4

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) 

(iii) NaCl solution

Zn(s) + NaCl(aq) → No reaction.

(iv) Dilute HCl 

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) 

(v) NaOH solution  

Zn(s) + 2NaOH(Aq.) → Na2ZnO2(Aq.) + H2(g)

Question: (i) Crystals of copper sulphate are being heated for a small time in a beaker. 

(a) What’s the color of copper sulphate crystals before and after they have been heated? 

(b) Name the source of liquid droplets observed on the inner upper side of the test tube while heating? 

(ii) A metal 'X' is dipped in an Aq. solution of aluminium sulphate and no reaction is seen whereas when it is dipped in an aq. solution of ferrous sulphate, the pale green solution changes to colorless. Can You Identify the metal 'X' with reason? 

Ans: (i) (a) The copper sulphate crystals Color before heating is blue and changes to white after heating. 

(b) The liquid droplets are the water droplets. The source of these liquid droplets is the water of crystallisation of hydrated copper sulphate crystals (CuSO4.5H2O). 

(ii) When metal ‘X' is dropped in an aqueous solution of aluminium sulphate, no reaction is noticed which signifies it is less reactive than aluminium. But when it is dropped in iron sulphate solution, the initial pale green solution turns colorless, so 'X' is more reactive than iron and thus displaces it from its solution. 

So, 'X' must be zinc. 

Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)

Question: (a) Justify combustion reaction being an oxidation reaction.

(b) State the reason behind silver not evolving hydrogen on reacting with dilute sulphuric acid?

(c) State the method to test that the hydrogen gas is evolved in a reaction. 

Ans: (a) Yes, combustion is an example of an oxidation reaction because when combustion takes place, oxygen is added up to the thing which is burning, this burning can only occur in the presence of Oxygen. 

(b) Silver is less reactive than hydrogen and so placed below hydrogen in the reactivity series. Less reactive Metals than hydrogen cannot displace hydrogen from acids. So, Silver does not displace H2 in dilute sulphuric acid solution. When silver metal is added to dilute sulphuric acid, no reaction takes place.

(c) Pop test is a common test used to check the evolution of hydrogen gas in any Reaction. When a candle is brought near the hydrogen gas, it produces a pop sound. Moreover, it Produces a pungent and irritating smell when evolved.

Question: Define neutralisation reactions. State the reason behind being named so and Give one example of this reaction. 

Ans: The reaction between an acid and bases is called a neutralization reaction.

The reaction produces salt and water. It is named so because the Acid and Base neutralize each other to form Water and Salt. The H+ ion and H- ions react to form H2O. 

Acid + Base → Salt + Water

Example: Formation of Sodium Chloride (Common Salt):

HCl + NaOH → NaCl + H2O

Read more:

CBSE X Related Questions

1.
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

      2.
      Balance the following chemical equations.
      (a) HNO3 +Ca(OH)2 \(→\) Ca(NO3)2 + H2
      (b) NaOH + H2SO4 \(→\) Na2SO4 + H2
      (c) NaCl + AgNO3 \(→\) AgCl + NaNO3 
      (d) BaCl + H2 SO4 \(→\) BaSO4 + HCl

          3.
          Why does the sky appear dark instead of blue to an astronaut?

              4.
              Show how you would connect three resistors, each of resistance 6 Ω, so that the combination has a resistance of 
              1. 9 Ω
              2. 4 Ω

                  5.
                  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

                      6.
                      Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m s−1.

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