school0 comments

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non Metals

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non Metals

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non Metals includes answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on Chemical reactions and equations chapter.

 

Page No: 40

1. Give an example of a metal which
(i) is a liquid at room temperature.

► Mercury

(ii) can be easily cut with a knife.
► Sodium

(iii) is the best conductor of heat.

► Silver

 
(iv) is a poor conductor of heat.
► Mercury and Lead
 

2.Explain the meanings of malleable and ductile.

Answer

Malleable:Substances that can be beaten into thin sheets are called malleable. For example, most of the metals are malleable.
Ductile: Substances that can be drawn into thin wires are called ductile. For example, most of the metals are ductile.

 
Page no: 46
 

1. Why is sodium kept immersed in kerosene oil?

Answer

Sodium is high reactive element. If it is kept in open it can explosively react with oxygen to catch fire. Hence to prevent accidental damage sodium is immersed in kerosene oil.

2. Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water

Answer

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

(ii) Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) + Heat
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) + Heat

3. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

Metal
Iron (II) sulphate
Cooper (II) sulphate
Zinc sulphate
Silver nitrate
A.
No reaction
Displacement
    
B.
Displacement
  
No reaction
  
C.
No reaction
No reaction
No reaction
Displacement
D.
No reaction
No reaction
No reaction
No reaction


Use the Table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.

Answer

(i) B is most reactive metal.
(ii) B will displace copper from copper sulphate.
(iii) Arrangement of metals in the order of decreasing reactivity B>A>C>D.

4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.

Answer

Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal.

When iron reacts with dilute H2SO4, iron (II) sulphate with the evolution of hydrogen gas is formed.
Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)

5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.


Answer

When zinc is added to iron (II) sulphate then it will displace the iron from iron sulphate solution as shown in the following chemical reaction.Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)

Page No: 49

1. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?

Answer

(i) The representation of elements with valence electrons as dots around the elements is referred to as electron-dot structure for elements.


(ii)


(iii) The ions present in Na2O are Na+ and O2– ions and in MgO are Mg2+ and O2– ions.

2. Why do ionic compounds have high melting points?

Answer

Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces. That is why ionic compounds have high melting points.

 
Page No: 53
 
1. Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
 
Answer
 

(i) Mineral: The naturally occurring compounds of elements are known as Mineral.
(ii) Ore: Minerals from which metals can be extracted profitably are known as ores.
(iii) Gangue: The impurities present in the ore such as sand, rocks etc are non as gangue.

2. Name two metals which are found in nature in the free state.

Answer

The metals at the bottom of the reactivity series are mostly found in free state. For example: gold, silver, and platinum.

3. What chemical process is used for obtaining a metal from its oxide?

Answer

A metal can be extracted from its oxide by the process of reduction.


Page No: 55

1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

Metal
Zinc
Magnesium
Copper
Zinc oxide
–
–
–
Magnesium oxide
–
–
–
Copper oxide
–
–
–


In which cases will you find displacement reactions taking place?

Answer

Metal
Zinc
Magnesium
Copper
Zinc oxide
No reaction
Displacement
No reaction
Magnesium oxide
No reaction
No reaction
No reaction
Copper oxide
Displacement
Displacement
No reaction


2. Which metals do not corrode easily?

Answer

Metals which have low reactivity such as silver, gold does not corrode easily.

3. What are alloys?

Answer

An alloy is the homogeneous mixture of two or more metals or metals and non metals. For example brass is an alloy of copper and zinc.

Excercise

1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2solution and aluminium metal
(c) FeSO4solution and silver metal
(d) AgNO3solution and copper metal.
► (d) AgNO3solution and copper metal.

2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) all of the above.
► (c) Applying a coating of zinc

3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron
► (a) calcium

4. Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.
► (c) zinc is more reactive than tin.

5. You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
 
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Anwer

(a) With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is malleable), then it is a metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and a switch to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.

(b) The above tests are useful in distinguishing between metals and non-metals as these are based on the physical properties. No chemical reactions are involved in these tests.
 

 
6. What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer
 
Those oxides that behave as both acidic and basic oxides are called amphoteric oxides.
Examples: aluminium oxide (Al2O3), zinc oxide (ZnO)
 

7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer

Iron and aluminium will displace hydrogen from dilute acids as they more reactive then hydrogen. Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.

Page No: 57

8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer

In the electrolytic refining of a metal M:
Anode → Impure metal M
Cathode → Thin strip of pure metal M
Electrolyte → Solution of salt of the metal M
 
9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.
(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?


(b) Write a balanced chemical equation for the reaction taking place.

Answer

(a)
(i) There will be no action on dry litmus paper.

(ii) The colour of litmus paper will turn red because sulphur is a non-metal and the oxides of non-metal are acidic in nature.

(b) S (s) + O2(g) → SO2 (g)

10. State two ways to prevent the rusting of iron.

Answer

Two ways to prevent the rusting of iron are:
→ Oiling, greasing, or painting: By applying oil, grease, or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.
→ Galvanisation:An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and moisture. Hence, rusting is prevented.
 

11. What type of oxides are formed when non-metals combine with oxygen?

Answer

When non-metals are combined with oxygen then neutral or acidic oxides are formed. Examples of acidic oxides are NO2, SO2 and examples of neutral oxides are NO, CO etc.

12. Give reasons

(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer

(a) Platinum, gold, and silver are used to make jewellery because they are very lustrous. Also, they are very less reactive and do not corrode easily.

(b) Sodium, potassium, and lithium are very reactive metals and react very vigorously with air as well as water.Therefore, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.
 

(c) Though aluminium is a highly reactive metal, it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make cooking utensils.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides.

13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Answer

Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in the lemon or tamarind neutralises the basis copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.

14. Differentiate between metal and non-metal on the basis of their chemical properties.

Answer

Metal
Non-metal
Metals are electropositive. Non-metals are electronegative.
Oxides of metal are basic in nature. Oxides of non-metals are acidic in nature.
Metals displace hydrogen from dilute acids. They can’t replace hydrogen from dilute acids.
Metals form chlorides which are electrovalent or ionic compounds. Non-metals form chlorides which are covalent compounds.
They react with water to form oxides and hydroxides. Some metals react with cold water, some with hot water, and some with steam. They do not react with water.

15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Answer

The solution he had used was Aqua regia. Aqua regia is Latin word which means ‘Royal Water’. It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It is capable of dissolving metals like Gold and Platinum. Since the outer layer of the gold bangles is dissolved in aqua regia so their weight was reduced drastically.

16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer

Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water. 3Fe + 4H2O → Fe3O4 + H2O
That is why copper is used to make hot water tanks, and not steel.

Important Links

Quick Revision Notes –Chapter 3 Metals and Non Metals

Most Important Questions-Chapter 3 Metals and Non Metals

Important MCQs- Chapter 3 Metals and Non Metals

Read More
school0 comments

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts includes answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on Chemical reactions and equations chapter.

 

Page No: 18

1. You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

Answer

If the colour of red litmus does not change then it is acid. If the colour of red litmus changes to blue then it is base. If there is slight change in the colour of red litmus (such as purple) then it is distilled water.

Page No: 22

1. Why should curd and sour substances not be kept in brass and copper vessels?

Answer

Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.

2. Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Answer

Hydrogen gas is usually liberated when an acid reacts with metal.

 
Take few pieces of zinc granules and add 5 ml of dilute H2SO4. Shake it and pass the gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas.
H2SO4 + Zn → ZnSO4 + H2 ↑
We can test the evolved hydrogen gas by its burning with a pop sound when a candle is brought near the soap bubbles.

3. Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Answer

CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)
Calcium Carbonate + Hydrochloric acid → Calcium Chloride + Carbon dioxide + Water

Page No: 25

1. Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Answer

When HCl or HNO3 are mixed with water then they dissolve in water to form H+ or H3O+ ions which shows their acidic character. For example just see the following reactions
HCl (aq) → H+ + Cl–
H+ + H2O → H3O+
When alcohols and glucose are mixed with water then they do not dissolve to form ions. Hence they do not show acidic character.

2. Why does an aqueous solution of an acid conduct electricity?

Answer

The presence of hydrogen (H+) or hydronium (H3O+) ions in the aqueous solution of an acid are responsible for conducting electricity.

3. Why does dry HCl gas not change the colour of the dry litmus paper?

Answer

Dry HCl gas not change the colour of the dry litmus paper because it has no Hydrogen ions (H+) in it.

4. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
 
Answer
 
Since the process of dissolving an acid in water is exothermic, it is always recommended that acid should be added to water. If it is done the other way, then it is possible that because of the large amount of heat generated, the mixture splashes out and causes burns.

5. How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?

Answer

When an acid is diluted, the concentration of hydronium ions (H3O+) per unit volume decreases. This means that the strength of the acid decreases.

6. How is the concentration of hydroxide ions (OH−) affected when excess base is dissolved in a solution of sodium hydroxide?

Answer

The concentration of hydroxide ions (OH−) would increase when excess base is dissolved in a solution of sodium hydroxide.

Page No: 28

1. You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

Answer

A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution. Therefore, the solution with pH = 6 is acidic and has more hydrogen ion concentration than the solution of pH = 8 which is basic.

2. What effect does the concentration of H+ (aq) ions have on the nature of the solution?

Answer

If the concentration of H+ (aq) ions is increased (>10-7) then the solution become acidic and if the concentration of H+ (aq) ions is decreased (<10-7) then the solution become basic in nature.

3. Do basic solutions also have H+ (aq) ions? If yes, then why are these basic?

Answer

Yes, basic solution also has H+ ions. However, their concentration is less as compared to the concentration of OH– ions that makes the solution basic.

4. Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?

Answer

If the soil is acidic and improper for cultivation, then to increase the basicity of soil, the farmer would treat the soil with quick lime or slaked lime or chalk.

Page No: 33

1. What is the common name of the compound CaOCl2?
► Bleaching Powder.

2. Name the substance which on treatment with chlorine yields bleaching powder?
► Calcium hydroxide [Ca(OH)2]

3. Name the sodium compound which is used for softening hard water.
► Washing soda (Na2CO3.10H2O)

4. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

Answer

When sodium hydrogen carbonate is heated then sodium carbonate and water is formed along with the evolution of carbon dioxide gas.

5. Write an equation to show the reaction between Plaster of Paris and water.

Answer

Exercise

1. A solution turns red litmus blue, its pH is likely to be
(a) 1
(b) 4
(c) 5
(d) 10
► (d) 10

2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains
(a) NaCl
(b) HCl 
(c) LiCl 
(d) KCl
► (b) HCl

3. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be
(a) 4 mL
(b) 8mL
(c) 12 mL 
(d) 16 mL
► (d) 16 mL

4. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
► (c) Antacid

5, Write word equations and then balanced equations for the reaction taking place when −
(a) dilute sulphuric acid reacts with zinc granules.
 
(b) dilute hydrochloric acid reacts with magnesium ribbon.
 
(c) dilute sulphuric acid reacts with aluminium powder.
 
(d) dilute hydrochloric acid reacts with iron filings.

Answer

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

(b) 2HCl (aq) + Mg (s) → MgCl2 (aq) + H2 (g)

(c) 3H2SO4 (aq) + 2Al (s) → Al2(SO4)3 (aq) + 3H2 (g)

(d) 6HCl (aq) + 2Fe (s) → 2FeCl3 (aq) + 3H2 (g)

6. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

Answer

Two nails are fitted on a cork and are kept it in a 100 mL beaker. The nails are then connected to the two terminals of a 6-volt battery through a bulb and a switch. Some dilute HCl is poured in the beaker and the current is switched on. The same experiment is then performed with glucose solution and alcohol solution.

Observations:
It will be observed that the bulb glows in the HCl solution and does not glow in the glucose solution.

Result:
HCl dissociates into H+and Cl−ions. These ions conduct electricity in the solution resulting in the glowing of the bulb. On the other hand, the glucose solution does not dissociate into ions. Therefore, it does not conduct electricity.


Conclusion:
From this activity, it can be concluded that all acids contain hydrogen but not all compounds containing hydrogen are acids.
That is why, though alcohols and glucose contain hydrogen, they are not categorised as acids.
 

7. Why does distilled water not conduct electricity, whereas rain water does?

Answer

Distilled water cannot conduct electricity because it does not contain ions while rain water conducts electricity as it contains ions due presence of dissolved salts in it.

8. Why do acids not show acidic behaviour in the absence of water?

Answer

Acids do not show acidic behaviour in the absence of water because the dissociation of hydrogen ions from an acid occurs in the presence of water only.

9. Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Answer

(a) Neutral →Solution D with pH 7
(b) Strongly alkaline →Solution C with pH 11
(c) Strongly acidic →Solution B with pH 1
(d) Weakly acidic →Solution A with pH 4
(e) Weakly alkaline →Solution E with pH 9
The pH can be arranged in the increasing order of the concentration of hydrogen ions as: 11 < 9 < 7 < 4 < 1.

10. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?

Answer

The fizzing will occur strongly in test tube A, in which hydrochloric acid (HCl) is added. This is because HCl is a stronger acid than CH3COOH and therefore produces hydrogen gas at a faster speed due to which fizzing occurs.

11. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Answer

The pH of milk is 6. As it changes to curd, the pH will reduce because curd is acidic in nature. The acids present in it decrease the pH.

12.A milkman adds a very small amount of baking soda to fresh milk.
 

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
 
Answer
 
(a) The milkman shifts the pH of the fresh milk from 6 to slightly alkaline because in alkaline condition, milk does not set as curd easily.

(b) Since this milk is slightly basic than usual milk, acids produced to set the curd are neutralized by the base. Therefore, it takes a longer time for the curd to set.

13. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Answer

The Plaster of Paris should be stored in a moisture-proof container as it absorbs water from moisture and turn into hard substance (Gypsum) as shown in following chemical equation.
 
14. What is a neutralization reaction? Give two examples.

Answer

A reaction in which an acid and base react with each other to give a salt and water is termed as neutralization reaction.For Example:
(i) NaOH + HCl → NaCl + H2O
(ii) HNO3 + KOH → KNO3 + H2O

15. Give two important uses of washing soda and baking soda.

Answer

Two important uses of washing soda are:
→ It is used in glass, soap, and paper industries.
→ It is used to remove permanent hardness of water.

Two important uses of baking soda are:
→ It is used as baking powder. Baking powder is a mixture of baking soda and a mild acid known as tartaric acid. When it is heated or mixed in water, it releases CO2 that makes bread or cake fluffy.
→ It is used in soda-acid fire extinguishers.

Important Links

Quick Revision Notes -Chapter 2 Acids, Bases and Salts

Most Important Questions-Chapter 2 Acids, Bases and Salts

Important MCQs- Chapter 2 Acids, Bases and Salts

Read More
school0 comments

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations includes answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on Chemical reactions and equations chapter.

 

NCERT Solutions for Class 10 Science Chapter 1 Intext Questions

(Page No. 6)

Question 1: Why should a magnesium ribbon be cleaned before burning in air?

Answer: A magnesium ribbon should be cleaned before burning because it is a reactive metal that reacts with oxygen from the air to form a stable, protective layer of magnesium oxide (MgO) on its surface. This layer prevents the magnesium underneath from burning properly. Cleaning the ribbon with sandpaper removes this oxide layer, allowing the pure magnesium to react with oxygen when heated.

Question 2: 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

Answer:
(i) H₂(g) + Cl₂(g) → 2HCl(g)

(ii) 3BaCl₂(aq) + Al₂(SO₄)₃(aq) → 3BaSO₄(s) + 2AlCl₃(aq)

(iii) 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

Question 3: Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions 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.

Answer:
(i) BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)
(Note: This is a precipitation reaction.)

(ii) NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)
(Note: This is a neutralization reaction.)

(Page No. 10)

Question 1: 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 (i) above with water.

Answer:
(i) The substance ‘X’ used for whitewashing is Calcium Oxide, also known as quicklime. Its chemical formula is CaO.

(ii) When calcium oxide (CaO) reacts with water (H₂O), it forms calcium hydroxide (Ca(OH)₂), also known as slaked lime. This reaction is highly exothermic, releasing a large amount of heat.

Chemical Equation:
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
(Quicklime) + (Water) → (Slaked Lime)

Question 2: Why is the amount of gas collected in one of the test tubes in Activity 1.7 (electrolysis of water) double of the amount collected in the other? Name this gas.

Answer:
In the electrolysis of water (H₂O), water decomposes into hydrogen gas (H₂) and oxygen gas (O₂). The balanced chemical equation for this reaction is:
2H₂O(l) →Electrolysis 2H₂(g) + O₂(g)

From the equation, we can see that two molecules of water produce two molecules of hydrogen gas and only one molecule of oxygen gas. This means the mole ratio of hydrogen to oxygen is 2:1.

Therefore, the volume of gas collected at the cathode (hydrogen) is double the volume of gas collected at the anode (oxygen).

The gas collected in double the amount is **Hydrogen gas (H₂)
**.

(Page No. 13)

Question 1: Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Answer:
When an iron nail is dipped in a copper sulphate solution, a displacement reaction occurs. Iron (Fe) is more reactive than copper (Cu). Therefore, iron displaces copper from the copper sulphate (CuSO₄) solution.

The blue colour of the copper sulphate solution fades and turns light green due to the formation of iron(II) sulphate (FeSO₄). A reddish-brown coating of copper metal is deposited on the iron nail.

Chemical Equation:
Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)
(Iron) + (Blue solution) → (Light green solution) + (Brown deposit)

Question 2: Give an example of a double displacement reaction other than the one given in Activity 1.10.

Answer:
An example of a double displacement reaction is the reaction between silver nitrate (AgNO₃) and sodium chloride (NaCl). When their aqueous solutions are mixed, a white precipitate of silver chloride (AgCl) is formed along with a solution of sodium nitrate (NaNO₃).

Chemical Equation:
AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
(Silver Nitrate) + (Sodium Chloride) → (Silver Chloride – white ppt) + (Sodium Nitrate)

Question 3: Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i) 4Na(s) + O₂(g) → 2Na₂O(s)
(ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l)

Answer:

  • Oxidation: Gain of oxygen or loss of hydrogen.
  • Reduction: Loss of oxygen or gain of hydrogen.

(i) 4Na(s) + O₂(g) → 2Na₂O(s)

  • Sodium (Na) is gaining oxygen to form Sodium Oxide (Na₂O). Therefore, Sodium (Na) is oxidised.
  • Oxygen (O₂) is being combined with sodium. Therefore, Oxygen (O₂) is reduced.

(ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l)

  • Copper Oxide (CuO) is losing oxygen to form Copper (Cu). Therefore, CuO is reduced.
  • Hydrogen (H₂) is gaining oxygen to form Water (H₂O). Therefore, H₂ is oxidised.

NCERT Solutions for Class 10 Science Chapter 1 Exercise Questions

Exercises

Page No: 14

1. Which of the statements about the reaction below are incorrect?
2PbO (s) + C (s) → 2Pb (s) + CO2 (g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.

(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all
► (i) (a) and (b)

2. Fe2O3 + 2Al → Al2O3 + 2Fe
The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
► (d) displacement reaction.

Page No: 15

3. What happens when dilute hydrochloric acid is added to iron filings? 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.
► (a) Hydrogen gas and iron chloride are produced.

4. What is a balanced chemical equation? Why should chemical equations be balanced?

Answer

A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation.Chemical reaction should be balanced to follow law of conservation of mass.

5. 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 a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Answer

(a) 3H2 (g) + N2 (g) → 2NH3 (g)

(b) 2H2S (g) + 3O2 (g) → 2H2O (l) + 2SO2 (g)

(c) 3BaCl2 (aq) + Al2(SO4)3 (aq) → 2AlCl3 (aq) + 3BaSO4 (s)

(d) 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

6. Balance the following chemical equations.

(i) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
(ii) NaOH + H2SO4 → Na2SO4 + H2O
(iii) NaCl + AgNO3 → AgCl + NaNO3
(iv) BaCl2 + H2SO4 → BaSO4 + HCl

Answer

(i) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O
(ii) 2NaOH + H2SO4 → Na2SO4 + 2H2O
(iii) NaCl + AgNO3 → AgCl + NaNO3
(iv) BaCl2 + H2SO4 → BaSO4 + 2HCl

7. 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

Answer

(a) Ca(OH)2 + CO2 → CaCO3 + H2O

(b) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag

(c) 2Al + 3CuCl2 → 2AlCl3 + 3Cu

(d) BaCl2 + K2SO4 → BaSO4 + 2KCl

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

(a)Potassium bromide (aq) + Barium iodide (aq)­ → Potassium iodide (aq) + Barium bromide(s)
(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)


Answer
 
(a) 2KBr (aq) + BaI2 (aq) → 2KI (aq) + BaBr2 (s): Double displacement reaction
 
(b) ZnCO3 (s) →  ZnO (s) + CO2 (g): Decomposition reaction

(c) H2 (g) + Cl2 (g) → 2HCl (g): Combination reaction
 


(d) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) : Displacement Reaction

9. What does one mean by exothermic and endothermic reactions? Give examples.

Answer

Chemical reactions that release energy in the form of heat, light, or sound are called exothermic reactions.
Example: C (g) + O2 (g) → CO2 + Heat Energy

Reactions that absorb energy or require energy in order to proceed are called endothermic reactions.
Example:

10. Why is respiration considered an exothermic reaction? Explain.
 
Answer
 
Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of heat energy.
C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) + Energy
 


11. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Answer

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.For Example:
Decomposition Reaction:
Combination Reaction:
CaO (s) + H2O (l) → Ca(OH)2 (aq)

Page No: 16

12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
 
Answer
 

13. What is the difference between displacement and double displacement reactions? Write equations for these reactions.

Answer

In a displacement reaction, a more reactive element replaces a less reactive element from a compound.
For Example: CuSo4 (aq) + Zn (s) → ZnSO4 (aq) + Cu (s)
 

In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.
For Example: Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl (aq)
 
14. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Answer

2AgNO3 (aq) + Cu (s) → Cu(NO3)2 (aq) + 2Ag (s)
Silver Nitrate + Copper → Copper Nitrate + Silver

15. What do you mean by a precipitation reaction? Explain by giving examples.

Answer

A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.For Example:
Na2CO3 (aq) + CaCl2 (aq) → CaCO3 (s) + 2NaCl (aq)
 

Sodium Carbonate + Calcium Chloride → Calcium Carbonate + Sodium Chloride
In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction.

16. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction

Answer

Oxidation Reaction: It is a chemical reaction in which gain of oxygen or loss of hydrogen takes place.
Reduction Reaction: It is a chemical reaction in which loss of oxygen or gain of hydrogen takes place.

17. A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Answer

‘X’ is copper (Cu) and the black-coloured compound formed is copper oxide (CuO). The equation of the reaction involved on heating copper is given below.

18. Why do we apply paint on iron articles?
Answer

Iron articles are painted because it prevents them from rusting. When painted, the contact of iron articles from moisture and air is cut off. Hence, rusting is prevented.

19. Oil and fat containing food items are flushed with nitrogen. Why?

Answer

Oil and fat containing food items flushed with nitrogen because nitrogen acts as an antioxidant and it prevents them from being oxidised.

20. Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity

Answer

Corrosion is defined as a process where materials, usually metals, deteriorate as a result of a chemical reaction with air, moisture, chemicals, etc.
For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.
4Fe + 3O2 + nH2O → 2Fe2O3.nH2O

Rancidity is the process of oxidation of fats and oils that can be easily noticed by the change in taste and smell is known as rancidity.
For example, the taste and smell of butter changes when kept for long.
 

Important Links

Quick Revision Notes – Chemical Reactions and Equations

Most Important Questions- Chemical Reactions and Equations

Important MCQs- Chemical Reactions and Equations

Read More
school0 comments

Ch 11 Human Eye and Colourful World | Ch-11 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Ch 11 Human Eye and Colourful World | Ch-11 Class 10 Science Quick Revision Notes

  The ability of the eye lens to adjust its focal length is called accommodation. Focal length can be changed with the help of ciliary muscles.

Pdf is Loading Please Wait …….

NCERT Solution –  Ch 11 Human Eye and Colourful World

Most Important Questions –Ch 11 Human Eye and Colourful World

Most Important MCQs –Ch 11 Human Eye and Colourful World

For Free, Video Lectures Click here

Read More
school0 comments

Sustainable Management of Natural Resources | Ch-16 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Sustainable Management of Natural Resources | Ch-16 Class 10 Science Quick Revision Notes

  Human activities lead to environmental problems such as depletion of ozone layer and production of huge amount of garbage.

Pdf is Loading Please Wait …….

NCERT Solution –  Sustainable Management of Natural Resources

Most Important Questions –Sustainable Management of Natural Resources

Most Important MCQs –Sustainable Management of Natural Resources

For Free, Video Lectures Click here

Read More
school0 comments

Our Environment | Ch-15 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Our Environment | Ch-15 Class 10 Science Quick Revision Notes

  Human activities lead to environmental problems such as depletion of ozone layer and production of huge amount of garbage.

Pdf is Loading Please Wait …….

NCERT Solution –  Our Environment

Most Important Questions –Our Environment

Most Important MCQs –Light -Our Environment

For Free, Video Lectures Click here

Read More
school0 comments

Sources of Energy | Ch-14 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Sources of Energy | Ch-14 Class 10 Science Quick Revision Notes

  A source of energy is one which provide adequate amount of energy in a convenient form over a long period of time.

Pdf is Loading Please Wait …….

NCERT Solution –  Sources of Energy

Most Important Questions –Sources of Energy

Most Important MCQs – Light -Sources of Energy

For Free, Video Lectures Click here

Read More
school0 comments

Magnetic Effects of Electric Current | Ch-13 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Magnetic Effects of Electric Current | Ch-13 Class 10 Science Quick Revision Notes

  Electromagnets and electric motors involve the magnetic effect of electric current, and electric generators involve the electric effect of moving magnets.

Pdf is Loading Please Wait …….

NCERT Solution –  Magnetic Effects of Electric Current

Most Important Questions –Magnetic Effects of Electric Current

Most Important MCQs –Light -Magnetic Effects of Electric Current

For Free, Video Lectures Click here

Read More
school0 comments

Electricity | Ch-12 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Electricity | Ch-12 Class 10 Science Quick Revision Notes

  Direction of current is taken opposite to flow of electrons as electrons were not known at the time when the phenomenon of electricity was discovered first and current was considered to be flow of positive charge.

Pdf is Loading Please Wait …….

NCERT Solution –  Electricity

Most Important Questions –Electricity

Most Important MCQs –Light – Electricity

For Free, Video Lectures Click here

Read More
school0 comments

Light – Reflection & Refraction| Ch-10 Class 10 SCIENCE Quick Revision Notes | NCERT CBSE | Edugrown

Light – Reflection & Refraction | Ch-10 Class 10 Science Quick Revision Notes

  Some common phenomena associated with lights are image formation by mirrors, the twinkling of stars, the beautiful colours of a rainbow, bending of light by a medium and so on.

Pdf is Loading Please Wait …….

NCERT Solution –  Light – Reflection & Refraction

Most Important Questions –Light – Reflection & Refraction

Most Important MCQs –Light – Reflection & Refraction

For Free, Video Lectures Click here

Read More