Chemical Reactions and Equations (Activity Based Questions & Answers) : Chapter 1

Learning and solving the Activity-based problems of this chapter will really help you in understanding chemistry and its formula in a very easy way.

Once you will understand the Activities of the chapter then you will be able to make formulas on your own. Memorizing Formulas in this way is really a super-easy way. So, understand each and every activity of any chapter. It will become very easy for you to memorize the formulas of the chapter.

Chemistry is the only part of Science in which you can easily score full marks in your Board exams. And especially form this chapter every year in board exams one Activity-based Question of 5 marks asked. So that’s why you can’t leave this chapter.

Then let’s get started.

Activity 1.1 :-

In this Activity, From the above Image, you understand the Procedure to do the reaction. But what you will get after the Reaction will be completed.

Watch the video below to understand the full Procedure:-

When you heat the Magnesium in the Presence of Oxygen Then it starts burning with the White Dazzling white Flame and then converted into the White color powder that is Magnesium Oxide (MgO).
 

Important Questions Related to this Activity :-

Q. What will happen when magnesium ribbon is burnt in air?
Ans. Magnesium ribbon burns with a dazzling flame and white powder is collected on the watch glass placed under it. The white powder is magnesium oxide formed by the reaction of magnesium and oxygen present in the air.

 

Q. What is the Color of magnesium?
Ans. The color of magnesium is silvery-white. And after Burning in the presence of Oxygen, the color Changes to white.
Magnesium (Mg) ⎯⎯→ Silvery White Color
Magnesium oxide (MgO)  ⎯⎯→ White color

 

Activity 1.2 :-

 

Again from the Above image, you Understand what the procedure to do for performing this reaction. Watch this video till end to understand the procedure with more clarification.

In this activity of NCERT, When Lead Nitrate [Pb(NO3)2] reacts with Potassium Iodide(KI), a yellow color of Precipitate (ppt.) is Formed. You can see above in the video, How the reaction takes place.

When two Colourless compound Lead nitrate and Potassium Iodide combine with each other, they form a new yellow color semi-soluble compound that is Lead Iodide (PbI2) which is insoluble in water. This reaction was also an example of a Double Displacement reaction.

Important Questions Related to this Activity :-

Q. What is Precipitation Reaction ?
Ans. This is a type of reaction in which when two Aqueous soluble solutions Combine/React together to form a semi-soluble Salt, that salt is called as Precipitate. And in any reaction, when Precipitate is formed then that is called a Precipitation reaction.

Q. Give some More Examples of Precipitation Reaction ?
Ans. Some more examples of Precipitation reactions are:-
        AgNO3(aq) + KCl(aq)  ⎯⎯→  AgCl(ppt.) + KNO3(aq)
        2KOH(aq) + CaCl2(aq)  ⎯⎯→  Ca(OH)2(aq) + 2KCl(aq)

Activity 1.3 :-

Once Again watch this Video and see the above image you will get the Clear-cut Knowledge about how to do perform this Activity.

 

In this activity, When you add Zn granules (very small pieces of zinc) to the dilute HCl (Hydrochloric acid) then you will observe the rise in Temperature of the Conical Flask and also hydrogen gas will produce.

You can feel the heat just by touching the Conical Flask and for Testing the Hydrogen, you can do a soap water test.

This is also an Exothermic Reaction as well as Displacement Reaction.

Important Questions Related to this Activity :-

Q. Why it is Recommended always to use Dilute Acids?
Ans. Because, If the Concentration of the Acid will be higher, then it will be a more Exothermic Reaction and if the activity will not be completed in the presence of the right mentor then it can be very harmful.

As you all know how acids are harmful if the concentration will be higher, it can even burn the skin. And to prevent Danger, we use the highly dilute Acid.

Q. What happens to zinc granules when dilute hydrochloric acid or sulphuric acid is added to it? Is there any change in its temperature?
Ans. Zinc being an active metal readily reacts with dil. hydrochloric acid at room temperature to form soluble zinc chloride and hydrogen. We can observe bubbles of hydrogen gas being formed around zinc granules. If we touch the conical flask, we can feel a sense of hotness as there is a rise in temperature. So, it’s a exothermic reaction.

Zn + 2HCl ⎯⎯→ ZnCl2 + H2

As zinc displaces hydrogen from HCl, this a displacement reaction. Hydrogen gas is usually prepared in the laboratory by this reaction.

When zinc granules are added to dilute sulphuric acid, there occurs a change in the state of zinc granules and they are converted to zinc sulphate(ZnSO4) and hydrogen gas is evolved.

Zn + H2SO4 ⎯⎯→ ZnSO4 + H2

This reaction is exothermic, i.e., it involves release of heat and so the flask becomes hot and temperature of the system increases.

Activity 1.4 :-

Calcium oxide(CaO) is also known as Quick Lime. & Calcium Hydroxide{Ca(OH)2} is Known as Slaked Lime.

In this Above Activity(1.4) when Calcium oxide (CaO) or Quick lime Reacts with H2O water then it produces Calcium Hydroxide[Ca(OH)2] or Slaked Lime. Also the heat is produced During this reaction. That’s why this is also an Example of Exothermic Reaction.

Important Questions Related to this Activity :-

Q. What happened when Calcium Oxide reacts with H2O? OR… What happened when Quick lime reacts with water?
Ans. When CaO (Quick lime/Calcium oxide) Reacts with the water to form a new compound called Slaked lime [Ca(OH)2]. Also, the heat is produced at the time of reaction.

Q. What are combination reactions ?
Ans. Such a reaction in which a single product is formed from two or more reactants is known as a combination reaction.

Q. Write some more examples of Combination Reactions?
Ans. (i) Burning of coal:-
        C(s) + O2(g) ⎯→ CO2(g)
        (ii) Formation of water:-
        2H2(g) + O2(g) ⎯→ 2H2O(l)

Activity 1.5 :-

In this Activity, When we heat the Green color crystals of FeSO4 (Iron Sulphate) then it gets converted into Fe2O3 (Iron oxide/ferric oxide) a reddish-brown colored Compound. Also the SO2 (Sulphur dioxide) and SO3 (Sulfur tri-Oxide) gas Releases.

Important Questions Related to this Activity :-

Q. Do you observe any change in the colour of ferrous sulphate crystals when they are heated in the boiling tube over the flame of a burner or spirit lamp?
Ans. The green colour of ferrous sulphate crystals changes to brownish black oxide and smell of burning sulphur will be observed. Ferrous sulphate decomposes to form ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide (SO3). So, the gas emitted smells like burning sulphur.

Q. Which type of reaction is taking place in this activity ?
Ans. In this reaction, the single reactant FeSO4 decomposes to form three different products. So, the reaction is a decomposition reaction.

Q. Give some examples of Decomposition Reaction?
Ans. 2FeSO4(s)  ⎯⎯→   Fe2O3(s) + SO2(g) + SO3(g)
        CaCO3(s)  ⎯⎯→  CaO(s) + CO2(g)
        2Pb(NO3)2(s)  ⎯⎯→  Heat 2PbO(s) + 4NO2(g) + O2(g)

Q. What is Wafting gas?
Ans. SO2 and SO3 are the colorless gases which are colorless and have pungent smell. These gases are harmful to health.

Activity 1.6 :-

Basically, This reaction is a Thermal Decomposition Reaction such as the upper one.

In this activity, When you will heat Lead nitrate [Pb(NO3)2] in the presence of heat then a brown color Nitrogen di-oxide (NO2) gas will produce.

• [message]
• NOTE :
  
•  Pb(NO3)2  ⎯⎯→   This is a White color compound and when we heat it in the Presence of Oxygen then NO2 gas is produced which is Brown in Colour.
  

Important Questions Related to this Activity :-

Q. What do you observe when a boiling test tube containing lead nitrate powder is heated it over a flame?
Ans. On heating lead nitrate decomposes with a crackling sound along with the evolution of brown fumes of nitrogen dioxide(NO2) which has an irritating smell. The gas turns blue Litmus red; hence, it is acidic in nature. A yellow solid residue of lead oxide (PbO) remains in the test tube. 

Q. What is the Equation for the Following Reaction?
Ans.

 

Activity 1.7 :-

Does this activity tell us about the Electroyotic decomposition Reaction?

Important Questions Related to this Activity :-

During the electrolysis of water, we observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes.

Q. Is the volume of the gas collected the same in both the test tubes?
Ans. The volume of the gas collected in both the test tubes is not the same. The volume of one of the gases, namely, hydrogen, is twice the volume of the gas(oxygen) collected in the other test tube.

Q. What happens to these gases when we bring a burning candle close to the mouth of each of the test tubes containing the gases?
Ans. When we bring a burning candle close to the mouth of one of the test tube, the gas in the test tube catches fire and burns with a pop sound indicating that the gas in the test tube is hydrogen whereas when a burning candle was introduced into the other test tube, the candle started burning brightly indicating that the test tube contained oxygen because the abundance of oxygen accelerates the combustion reaction. The higher the oxygen concentration is, the more vigorously the candle will burn.

Q. Which gas is present in each test tube?
Ans. The gas collected at the anode is oxygen and the gas collected at the cathode is hydrogen.

Q. Why the amount of one gas produced in one Test tube is Double than the other one?
Ans:- H2 + O2 ⎯→  H2O

Hydrogen gas and the oxygen gas formed are always in the ratio of 2:1 in 1 molecules of water. Therefore the volume of gas collected in the first test tube is double the volume of the gas collected in the second test tube.

Activity 1.8 :-

This reaction is the Example of Photolytic decomposition Reaction. In the above image, it is clearly defined as the procedure of the Reaction.

In this activity, When we keep Silver Chloride (AgCl) in the presence of Sunlight then the Silver-white color of the Silver Chloride changes to Grey.

This is Because of the Decomposition of the AgCl to Silver and Chlorine gas.

2AgCl(s) ⎯→2Ag(s) + Cl2(g)

Important Questions Related to this Activity :-

Q. Why AgCl kept in a Black color of Bottle ?
Ans. As you know now, AgCl is a photolytic decomposing material that’s why we keep AgCl in a black color bottle to protect it from the Sunlight. Because when AgCl comes in contact with Sunlight, then it starts decomposing.

Q. Give some examples of more Photolytic Docomposing Substances and their Relations ?
Ans. 2AgBr(s) + Sunlight   ⎯→  2Ag(s) + Br2(g)

Q. Which Reaction is Used for Black and White Photography?
Ans. 2AgBr(s) + Sunlight  ⎯→  2Ag(s) + Br2(g)

This reaction is also Similar to the Above one(2AgCl  ⎯→  2Ag + Cl2). And this Reaction (Photolytic Decomposition of Silver Bromide) is used for the Black and white Photography.

• [message]
•  Name and write the reaction which is used in black and white photography.
• Silver chloride when kept in the sun decomposes to form silver and chlorine gas.
  
  The white silver chloride powder turns grey due to the formation of silver and with the release of chlorine gas.
  
  
   
  Similarly, silver bromide also undergoes decomposition to give silver with the release of bromine gas when exposed to air.
  
  
  Since the reactions are sensitive to light they are used in black and white photography.

Activity 1.9 :-

See the above Image, What will be the Procedure to do this Activity.

This activity tells us About the Displacement Reaction that how it takes place what changes we can observe after the reaction will takes place.

Important Questions Related to this Activity :-

Q. Why does the Iron nail become brownish in color and the blue color of copper sulfate solution fade?

Ans. In this reaction, the Iron nail becomes brownish in color and the blue color of copper sulfate solution fade Because Iron displaces Cu (Copper) from its Positon (CuSO4) Copper Sulphate. Because Iron is more reactive than Copper and it easily displaces Cu(Copper) from Copper Sulphate(CuSO4).
And that’s why the color of CuSO4 solution changes from Blue color to fade because finally the solution of Copper sulfate was got to converted into Iron Sulphate (FeSO4).
Fe(s) + CuSO4(aq)  ⎯⎯→  FeSO4(aq) + Cu(s)

Activity 1.10 :-

Q. What do you observe ?
Ans. As you know, This reaction is an Example of Double Displacement Reaction. When 3 ml of sodium sulphate solution is mixed with 3 mL of barium chloride solution in a test tube, a white precipitate of barium sulphate is formed. Any reaction that produces a precipitate can be called a precipitation reaction.

Activity 1.11 :-

Q. What happens to the Copper ?
Ans. The surface of copper powder becomes coated with black copper(II) oxide. This is because oxygen is added to copper and copper oxide is formed.

Hope you all find your answer if you have any doubt related to this topic then please let me known in the comment section.

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