NCERT Exemplar Solutions Class 10 Science Chemical Reactions And Equations

Read NCERT Exemplar Solutions Class 10 Science Chemical Reactions And Equations below, students should study NCERT Exemplar class 10 Science available on Studiestoday.com with solved questions and answers. These chapter wise answers for class 10 Science Exemplar problems have been prepared by teacher of Grade 10. These NCERT Exemplar class 10 Science solutions have been designed as per the latest NCERT syllabus for class 10 and if practiced thoroughly can help you to score good marks in standard 10 Science class tests and examinations

Multiple Choice Questions.......................


Question 1: Which of the following is not a physical change?

(a) Boiling of water to give water vapour

(b) Melting of ice to give water

(c) Dissolution of salt in water

(d) Combustion of Liquefied Petroleum Gas (LPG) 

Solution 1:  (d) Combustion of Liquefied Petroleum Gas (LPG) 

Combustion is often a chemical change since it results in the formation of a new compound that is unstoppable.

 

Question 2:  The following reaction is an example of a:

4NH3 (g) + 5O2 (g) → 4NO(g) + 6H2O(g)

(i) displacement reaction

(ii) combination reaction

(iii) redox reaction

(iv) neutralisation reaction

(a) (i) and (iv)

(b) (ii) and (iii)

(c) (i) and (iii)

(d) (iii) and (iv) 

Solution 2:  (c)  (i) and (iii) 

The given reaction is a hybrid of displacement and redox reactions. The displacement reaction occurs when oxygen displaces hydrogen in ammonia. A redox reaction occurs when nitrogen is oxidised and oxygen is reduced.

 

Question 3:  Which of the following statements about the given reaction are correct?

3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2 (g)

  1. Iron metal is getting oxidised
  2. Water is getting reduced
  3. Water is acting as a reducing agent
  4. Water is acting as an oxidising agent

(a) (i), (ii) and (iii)

(b) (iii) and (iv)

(c) (i), (ii) and (iv)

(d) (ii) and (iv) 

Solution 3:  (c) (i), (ii) and (iv) 

Here, oxygen reacts with water to produce oxidation. The amount of oxygen in water is decreasing as a result of the removal of oxygen. Water is an oxidising agent as well as a source of oxygen.

 

Question 4:  Which of the following are exothermic processes? 

(i) The reaction of water with quick lime

(ii) Dilution of an acid

(iii) Evaporation of water

(iv) Sublimation of camphor (crystals)

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv) 

Solution 4:  (a) (i) and (ii) 

Exothermic reactions release a lot of heat, so when water reacts with fast lime and acid reacts with water, a lot of heat is released.

 

Question 5:  Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas, in the case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?

(i) In beakers A and B, the exothermic process has occurred.

(ii) In beakers A and B, the endothermic process has occurred.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

(a) (i) only

(b) (ii) only

(c) (i) and (iv)

(d) (ii) and (iii) 

Solution 5: (c) (i) and (iv)

Temperature will rise in exothermic processes, and temperature will fall in endothermic processes.

 

Question 6:  A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?

(a) KMnO4 is an oxidising agent, it oxidises FeSO4

(b) FeSO4 acts as an oxidising agent and oxidises KMnO4

(c) The colour disappears due to dilution; no reaction is involved

(d) KMnO4 is an unstable compound and decomposes in the presence of FeSO4 to a colourless compound. 

Solution 6:  (a) KMnO4 is an oxidising agent, it oxidises FeSO4 

The oxidising agent in this reaction is potassium permanganate (KMnO4).

The KMnO4 in the solution gives it a purple colour, which fades when all of the KMnO4 in the solution is used up.

 

Question 7:  Which among the following is (are) double displacement reaction(s)?

(i) Pb + CuCl2 → PbCl2 + Cu

(ii) Na2 SO4 + BaCl2 → BaSO4 + 2NaCl

(iii) C + O2 → CO2

(iv) CH4 + 2O2 → CO2 + 2H2O

(a) (i) and (iv)

(b) (ii) only

(c) (i) and (ii)

(d) (iii) and (iv) 

Solution 7: (b) (ii) only 

It's a double displacement reaction because sodium and barium are displaced from each other's salts.

 

Question 8:  Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to

(i) the formation of silver by decomposition of silver chloride

(ii) sublimation of silver chloride

(iii) decomposition of chlorine gas from silver chloride

(iv) oxidation of silver chloride

(a) (i) only

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (iv) only 

Solution 8:  (a) (i) only 

When silver chloride is exposed to sunlight for long duration it turns grey due to the formation of silver by decomposition of silver chloride.

 

Question 9:  Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by the liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv) 

Solution 9: (b) (ii) and (iii) 

As solid calcium oxide reacts vigorously with water, calcium hydroxide is formed, along with heat generation. This occurrence demonstrates that the reaction is exothermic. Since metal oxides and hydroxides are alkaline, the pH of the solution will be greater than 7.

 

Question 10:  Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

(i) Displacement reaction

(ii) Precipitation reaction

(iii) Combination reaction

(iv) Double displacement reaction

(a) (i) only

(b) (ii) only

(c) (iv) only

(d) (ii) and (iv) 

Solution 10: (c) (iv) only 

The elements ammonium and barium are being displaced from their salts. As a result, we have a double displacement reaction.

 

Question 11:  Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

(a) 1:1

(b) 2:1

(c) 4:1

(d) 1:2 

Solution 11:  (b) 2:1 

2 moles of hydrogen and 1 mole of water make up 1 mol of water. As a result, the mole ratio of hydrogen to oxygen is 2:1.

 

Question 12:  Which of the following is(are) an endothermic process(es)?

(i) Dilution of sulphuric acid

(ii) Sublimation of dry ice

(iii) Condensation of water vapours

(iv) Evaporation of water

(a) (i) and (iii)

(b) (ii) only (c)

(c) (iii) only

(d) (ii) and (iv) 

Solution 12: (d) (ii) and (iv) 

Sublimation of dry ice and evaporation are also endothermic reactions since the change from solid to gas or liquid to gas absorbs heat. 

 

Question 13: In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

(a) Lead sulphate (insoluble)

(b) Lead acetate

(c) Ammonium nitrate

(d) Potassium sulphate 

Solution 13: (b) Lead acetate 

We need a lead-containing compound to make lead iodide, so ammonium nitrate and potassium sulphate are out. Since lead sulphate is insoluble, the correct answer is (b) lead acetate.

 

Question 14:  Which of the following gases can be used for storage of fresh sample of an oil for a long time?

(a) Carbon dioxide or oxygen

(b) Nitrogen or oxygen

(c) Carbon dioxide or helium

(d) Helium or nitrogen 

Solution 14: (d) Helium or nitrogen

Since oxygen is an oxidising agent, it cannot be used. Since helium is an inert gas, it can be used. Nitrogen is less reactive than Helium and is therefore less expensive. Nitrogen is often used in packets to avoid rancidity.

 

Question 15:  The following reaction is used for the preparation of oxygen gas in the laboratory

2KClO3(s)HeatCatalyst2KCl(s)+3O2(g)

Which of the following statement(s) is(are) correct about the reaction?

(a) It is a decomposition reaction and endothermic in nature

(b) It is a combination reaction

(c) It is a decomposition reaction and accompanied by the release of heat

(d) It is a photochemical decomposition reaction and exothermic in nature 

Solution 15:  (a) It is a decomposition reaction and endothermic in nature 

When potassium chlorate decomposes, potassium chloride and oxygen are released. This is a naturally occurring endothermic decomposition reaction.

 

Question 16:  Which one of the following processes involves chemical reactions?

(a) Storing of oxygen gas under pressure in a gas cylinder

(b) Liquefaction of air

(c) Keeping petrol in a china dish in the open

(d) Heating copper wire in presence of air at high temperature 

Solution 16:  (d) Heating copper wire in the presence of air at high temperature 

There is no chemical reaction in the first three options presented here. Copper undergoes an oxidation reaction in the presence of air at high temperatures, resulting in copper oxide.

 

Question 17:  In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

a. 2H2(I)+O2(I)→2H2O(g)

b. 2H2(g)+O2(0)→2H2O(I)

c. 2H2(g)+O2(g)→2H2O(I)

d. 2H2(9)+O2(g)→2H2O(g) 

Solution 17: (c) 2H2(g)+O2(g)→2H2O(I) 

Since hydrogen and oxygen are gases at room temperature and water is a liquid in nature, choice c) reflects the correct states of reactants and products.

 

Question 18:  Which of the following are combination reactions?

  1. 2KClO3⟶ heat 2KCl+302
  2. MgO+H2O⟶Mg(OH)2
  3. 4Al+3O2⟶2Al2O3
  4. Zn+FeSO4⟶ZnSO4+Fe

(a) (i) and (iii)

(b) (iii) and (iv)

(c) (ii) and (iv)

(d) (ii) and (iii) 

Solution 18:  (d) (ii) and (iii) 

Option ii) and iii) describe combination reactions, in which two reactants react to form a single product.
 
 
Short Answer Questions............................

Question 19:  Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.

(b) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.

(c) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2 SO4.

(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light. 

Solution 19:

(a) N2(g)+3H2(g)= catalyst 773K2NH2(g)

It is a combination reaction. 

(b) NaOH(aq)+CH3COOH(aq)⟶CH3COONa(aq)+H2O(l)

It's a reaction in which a heavy base interacts with a weak acid to neutralise it, hence it is a neutralisation reaction. 

(c) C2H5OH(aq)+CH3COOH(l)⟶CH3COO C2H5(aq)+H2O(t)

It is a neutralisation reaction and double displacement reaction. 

(d) C2H4(g)+3O2(g)→2CO2(g)+2H2O(g)+ Heat + Light 

It is an oxidation reaction.

 

Question 20:  Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

(a) Thermite reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.

(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.

(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.

(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat. 

Solution 20:

(a) Fe2O3  + 2Al → Al2O3(s) + 2Fe (l)

It is Single displacement reaction. 

(b) 3Mg(s) + N→ Mg3N2

It is Combination reaction. 

(c) Cl2(g) + 2KI (aq) → 2KCl (Aq) + I2(s)

It is Single displacement reaction. 

(d) C2H5OH + 3O2 → 2CO2 + 3H2O + Heat

It is Combustion reaction.

 

Question 21:  Complete the missing components/variables given as x and y in the following reactions

(a) Pb(NO3 )2 (aq) + 2KI(aq) → PbI2 (x) + 2KNO3 (y)

(b) Cu(s) + 2Ag NO3 (aq) → Cu(NO3 )2 (aq) + x(s)

(c) Zn(s) + H2 SO4 (aq) → ZnSO4 (x) + H2 (y)

(d) CaCO3 (s) + x  CaO(s) + CO2 (g) 

Solution 21:

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

(b) Cu(s) + 2Ag NO3 (aq) → Cu(NO3 ) 2 (aq) + 2Ag(s)

(c) Zn(s) + H2 SO4 (aq) → ZnSO4 (aq) + H2 (g)

(d) CaCO3 (s) + Heat → CaO(s) + CO2 (g)

 

Question 22:  Which among the following changes are exothermic or endothermic in nature?

(a) Decomposition of ferrous sulphate

(b) Dilution of sulphuric acid

(c) Dissolution of sodium hydroxide in water

(d) Dissolution of ammonium chloride in water 

Solution 22:

(a) Decomposition of ferrous sulphate: Endothermic reaction

(b) Dilution of sulphuric acid: Exothermic reaction

(c) Dissolution of sodium hydroxide in water: Exothermic reaction

(d) Dissolution of ammonium chloride in water: Endothermic reaction

 

Question 23:  Identify the reducing agent in the following reactions

(a) 4NH3 + 5O2 → 4NO + 6H2O

(b) H2O + F2 → HF + HOF

(c) Fe2O3 + 3CO → 2Fe + 3CO2

(d) 2H2 + O2 → 2H2O 

Solution 23:

(a) 4NH3 + 5O2 → 4NO + 6H2O

Reducing agent is NH3 

(b) H2O + F2 → HF + HOF

Reducing agent is F2 

(c) Fe2O3 + 3CO → 2Fe + 3CO2

Reducing agent is CO 

(d) 2H2 + O2 → 2H2O

Reducing agent is H2

 

Question 24:  Identify the oxidising agent (oxidant) in the following reactions

(a) Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O

(b) 2Mg + O2 → 2MgO

(c) CuSO4 + Zn → Cu + ZnSO4

(d) V2O5 + 5Ca → 2V + 5CaO

(e) 3Fe + 4H2O → Fe3O4 + 4H2

(f) CuO + H2 → Cu + H2O 

Solution 24:

(a) Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O

Oxidising agent is Pb3O4 

(b) 2Mg + O2 → 2MgO

Oxidising agent is O2 

(c) CuSO4 + Zn → Cu + ZnSO4

Oxidising agent is CuSO4 

(d) V2O5 + 5Ca → 2V + 5CaO

Oxidising agent is V2O5 

(e) 3Fe + 4H2O → Fe3O4 + 4H2

Oxidising agent is H2

(f) CuO + H2 → Cu + H2O

Oxidising agent is CuO

 

Question 25:  Write the balanced chemical equations for the following reactions

(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.

(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.

(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2 I2 ), liberates iodine gas and also forms potassium sulphate. 

Solution 25:

(a) Na2CO3 + HCl → NaCl + NaHCO3

(b) NaHCO3 + HCl → NaCl + H2O + CO2

(c) 2CuSO4+4Kl →2K2SO4+CU2I2+I2

 

Question 26:  A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of chemical reaction? 

Solution 26:   KCl (aq) + AgNO3 (aq) → AgCl (s) + KNO3 (aq)

This is a reaction of double displacement and precipitation.

  

Question 27:  Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction. 

Solution 27:   2FeSO4 → Fe2O3 +SO2+  SO3

This is a reaction of decomposition.

 

Question 28:  Why do fireflies glow at night? 

Solution 28:   Fireflies shine at night due to a chemical reaction that occurs within their bodies. In the presence of an enzyme called luciferase, oxygen interacts with calcium, ATP, and luciferin. Bioluminescence is the result of this process.

 

Question 29:  Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change? 

Solution 29:   Because of the plant's protective mechanism, grapes on the vine do not ferment. When grapes are plucked from the vine, yeast reacts with them to start the fermentation process. A chemical transition occurs as sugar converts into alcohol.

 

Question 30:  Which among the following are physical or chemical changes?

(a) Evaporation of petrol

(b) Burning of Liquefied Petroleum Gas (LPG)

(c) Heating of an iron rod to red hot.

(d) Curdling of milk                     

(e) Sublimation of solid ammonium chloride 

Solution 30:  

(a) Evaporation of petrol is Physical change.

(b) Burning of Liquefied Petroleum Gas (LPG) is Chemical change.

(c) Heating of an iron rod to red hot is Physical change.

(d) Curdling of milk is Chemical change.

(e) Sublimation of solid ammonium chloride is Physical change.

 

Question 31:  During the reaction of some metals with dilute hydrochloric acid, the following observations were made.

(a) Silver metal does not show any change

(b) The temperature of the reaction mixture rises when aluminium (Al) is added.

(c) The reaction of sodium metal is found to be highly explosive

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

Explain these observations giving suitable reasons. 

Solution 31:

(a) Since silver belongs to the low reactive series of metals, there will be no reaction between it and dilute HCL.

(b) As aluminium (Al) is applied to the reaction mixture, the temperature of the reaction mixture increases since it is an exothermic reaction.

(c) Sodium is a highly reactive metal that forms an exothermic reaction with atmospheric oxygen, resulting in an increase in temperature.

(d) As lead reacts with acid, it creates hydrogen gas, which is what causes bubbles to form.

 

Question 32:  A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved. 

Solution 32:  Calcium oxide is Compound X. In the cement industry, calcium oxide is widely used. When CaO is treated with water, it produces Ca(OH)2, an alkaline compound that changes the colour of red litmus to blue.

Ca + H2O → Ca(OH)2                                                                                                                       

  

Question 33:  Write a balanced chemical equation for each of the following reactions and also classify them.

(a) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.

(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.  

(c) Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.

(d) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water. 

Solution 33:

(a) Pb(CH3COO)2 + 2HCI → PbCl2 + CH3COOH

This is a reaction of double displacement.

 

(b) 2Na + 2C2H5OH → 2C2H5ONa+ H2

This is a reaction of displacement.

 

(c) Fe2O3 + 3CO → 2Fe + 3CO2

This is a reduction-oxidisation reaction.

 

(d) 2H2S+O→ 2S + 2H2O

This is a reaction of displacement.

 

Question 34:  Why do we store silver chloride in dark coloured bottles? 

Solution 34:   As silver chloride is exposed to sunlight, it decomposes into silver and chlorine gas. Consequently Dark-coloured bottles are used to store silver chloride.

 

Question 35:  Balance the following chemical equations and identify the type of chemical reaction.

(a) Mg (s) + Cl2 (g) → MgCl2 (s)

(b) HgO (s) Heat → Hg (l) + O2 (g)

(c) Na (s) + S (s) → Fuse Na2S (s)

(d) TiCl4 (l) + Mg (s) → Ti (s) + MgCl2 (s)

(e) CaO (s) + SiO2 (s) → CaSiO3 (s)

(f) H2O2 (l) → H2O (l) + O2 (g) 

Solution 35:

(a) Mg (s) + Cl2(g) → MgCl2 (s)

A synthesis reaction or a mixture reaction is the name for this form of reaction.

 

(b) 2HgO (s) — (Heat) → 2 Hg(I) + O2(g)

This is a thermal decomposition reaction in reality.

 

(c) 2Na(s) + S(s) — (Fuse) → Na2S(s)

This is a Combination reaction in nature.

 

(d) TiCI4 (l) + Mg(s) → Ti(s) + 2MgCl2 (s)

This reaction is classified as a displacement reaction.

 

(e) Cao(s) + SiO2(s) + CaSiO3(s)

This is a reaction of synthesis.

 

(f) 2H2O2 (I) — UV → 2H2O (I) + O2 (g)

This is a reaction of decomposition.

 

Question 36:  A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.

(a) Write the chemical formulae of X and Y.

(b) Write a balanced chemical equation, when X is dissolved in water. 

Solution 36:  

2Mg + O₂ → 2MgO

(a) Compound X is MgO [Magnesium Oxide]

Compound Y is Mg₃N₂ [Magnesium Nitride]

(b) Magnesium Hydroxide is formed when magnesium oxide is dissolved in water.

MgO  + H₂O → Mg(OH)₂

 

Question 37:  Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why? 

Solution 37:   Zinc is more reactive than copper since it is placed above hydrogen in the activity sequence of metals whereas copper is placed below hydrogen. As a consequence, Zinc interacts with HCl, while Copper does not.

 

Question 38:  A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining. 

(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.

(b) Name the black substance formed and gives its chemical formula. 

Solution 38:

(a) Silver combines with H2S in the atmosphere to form Silver Sulphide, a black-coloured compound. Corrosion is the name for this occurrence.

(b) Silver Sulphide is the dark-coloured substance that results.

2Ag + H2S → Ag2S + H2

 

Long Answer Questions.............................


Question 39:  On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed

(a) Write a balanced chemical equation of the reaction.

(b) Identity the brown gas X evolved.

(c) Identify the type of reaction.

(d) What could be the pH range of aqueous solution of the gas X? 

Solution 39:

NCERT Exemplar Solutions Class 10 Science Chemical Reactions And Equations

(b) Nitrogen dioxide, or NO2, is the brown gas X.

(c) Thermal decomposition is the reaction involved.

(d) Since NO2 dissolves in water and forms an acidic solution, the pH is 7. (pH range below 7).

 

Question 40:  Give the characteristic tests for the following gases

(a) CO2

(b) SO2

(c) O2

(d) H2 

Solution 40:

(a) CO2 is injected into limewater, which allows the water to turn milky. This is the carbon-dioxide presence validation measure.

(b) The scent of SO2, which smells like a rotten egg, is a distinguishing attribute.

(c) An oxygen test involves lighting a match stick near oxygen, which causes it to burn brighter.

(d) When a burning matchstick is brought close to H2 gas, the flame pops out. This is the procedure used to prove the presence of hydrogen gas.

 

Question 41:  What happens when a piece of

(a) zinc metal is added to copper sulphate solution?

(b) aluminium metal is added to dilute hydrochloric acid?

(c) silver metal is added to copper sulphate solution?

Also, write the balanced chemical equation if the reaction occurs. 

Solution 41:  

a) As zinc is applied to a copper sulphate solution, copper is displaced and Zinc sulphate is formed.

Zn(s) + CuSo4(aq) → ZnSo4(aq) + Cu(s)

 

b) Aluminium metals react with dilute HCl to form Aluminium Chloride, which creates hydrogen gas.

2Al (s) + 6HCl(aq) → 2AlCl3(aq) + 3H2

 

c) There will be no reaction when silver metal is applied to Copper Sulphate solution since silver is a non-reactive metal.

 

Question 42:  What happens when zinc granules are treated with a dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if a reaction occurs. 

Solution 42:   As zinc granules react with dilute H2SO4, a displacement reaction occurs, resulting in the formation of ZnSo4 and the release of H2

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

As zinc granules react with diluted HCl, a displacement reaction occurs, resulting in the formation of ZnCl2 and the release of H2

Zn (s) + H2Cl (aq) → ZnCl(aq) + H2 (g)                                                                            

Zinc granules react with dilute HNO3 to form Zinc nitrate, which creates H2O and nitrous oxide.

4Zn (s) + 10HNO3 (aq) → 4Zn(NO3)2 (aq) + 5H2O (i) + N2O (g) 

There will be no reaction when zinc granules react with NaCl.                            

When Zinc granules react with diluted NaOH solution, resulting in the formation of Na2ZnOaqueous solution and release of Hydrogen gas will take place.

Zn (s) + NaOH (aq) → Na2ZnO(aq)  + H2 (g)

 

Question 43:  On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, a white precipitate is obtained.

(a) Write a balanced chemical equation of the reaction involved

(b) What other names can be given to this precipitation reaction?

(c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why? 

Solution 43:

a) When a drop of Barium Chloride solution is applied to an aqueous solution of sodium sulphite, barium sulphite, a white precipitate, is created.

BaCl2 + Na2SO3—>BaSO3 + 2NaCl

 

b) The precipitation reaction is a double displacement in this case.

 

c) Barium chloride, Sulphur dioxide, and water are produced when dilute HCl is added to this reaction mixture. Since barium chloride is a soluble material, it can dissolve the white precipitate.

BaSO3 + HCl→ BaCl3 + SO2 + H2O

 

Question 44:  You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and H2O. In which of the above containers these solutions can be kept? 

Solution 44:   Since copper is a noble metal that does not react with HCl or even HNO3, these solutions can be stored in a copper jar. Aluminium reacts with acids to form zinc chloride if the solution is stored in an aluminium container.

Copper and aluminium do not react with each other, so water can be contained in either.

 

Chapter 16 Sustainable Management of Natural Resources
NCERT Exemplar Solutions Class 10 Science Management of Natural Resources