CLASS 10TH Chapter 1 - Chemical Reactions and Equations

Question 1:

Zinc oxide (ZnO) reacts with carbon (C) to produce zinc (Zn) and carbon monoxide (CO). The balanced chemical equation for the given reaction is 

ZnOs + Cs →Zns + COg

Which of the following substances is reduced in the given reaction?

Solution :

The given reaction is an example of a redox reaction. In a redox reaction, the substance that either gains oxygen or loses hydrogen is oxidised and the substance that loses oxygen or gains hydrogen is reduced.

In the given reaction, zinc oxide (ZnO) loses oxygen to form zinc (Zn). Hence, ZnO is reduced in the given reaction.

Hence, the correct answer is option A.

Option1 :

ZnO

Option2 :

C

Option3 :

Zn

Option4 :

CO

Option5 :

Question 2:

Calcium reacts with hydrochloric acid to produce

Solution :

It is an example of a displacement reaction. Calcium reacts with hydrochloric acid to produce calcium chloride and hydrogen gas. The chemical equation involved in the reaction can be represented as:

  Ca s     +     2HCl aq    →    CaCl2 aq   +   H2 gCalcium   Hydrogen chloride   Calcium chloride   Hydrogen

Hence, the correct answer is option C.

Option1 :

Cl2

Option2 :

H2

Option3 :

H2 and CaCl2

Option4 :

CaCl2 and Cl2

Option5 :

Question 3:

Use the following information to answer the next question.

The given equation represents the reaction of sodium metal with water. Sodium + Water → Sodium hydroxide + Hydrogen

Which of the following chemical equations represents a complete balanced chemical equation for the given word equation?

Solution :

In a balanced chemical equation, the number of atoms of every element on both sides of the equation must be equal. Among the given alternatives, the equation in alternative D represents a balanced chemical equation for the given reaction as the numbers of atoms of sodium, hydrogen, and oxygen on both sides of the equation are equal.

The given table shows that the number of atoms of each element on the reactant and product sides of the chemical equation.

Elements	Number of atoms in reactants	Number of atoms in products
Na	2	2
O	2	2
H	4	4

Therefore, the equation given in alternative D represents the balanced chemical equation for the given reaction.

Hence, the correct answer is option D.

Option1 :

2Na (s)+ H2O (l)→2NaOH (aq) + H2 (g)

Option2 :

Na (s)+ 2H2O (l)→NaOH (aq) + 2H2 (g)

Option3 :

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

Option4 :

2Na (s)+ 2H2O (l)→2NaOH (aq) + H2 (g)

Option5 :

Question 4:

In the process of respiration, glucose combines with oxygen in the cells of our body and a large amount of energy is . Hence, respiration is an process.

The information in which alternative completes the given statements?

Solution :

In the process of respiration, glucose reacts with oxygen in the cells of our body to produce carbon dioxide and water. Large amount of energy is released during this process. This chemical reaction can be represented by the following equation.

C6H1206 + 6O2 � →  6CO2 �  +  6H2O � + EnergyGlucose    Oxygen    Carbon dioxide   water                                    

The reactions in which energy is released are known as exothermic reactions. Therefore, respiration is an exothermic process.

Hence, the correct answer is option C.

Option1 :

i	ii
released	endothermic

Option2 :

i	ii
absorbed	endothermic

Option3 :

i	ii
released	exothermic

Option4 :

i	ii
absorbed	exothermic

Option5 :

Question 5:

Aluminium reacts with copper sulphate to produce

Solution :

The given reaction is a displacement reaction. As aluminium is more reactive than copper, it displaces copper from the copper sulphate solution to produce copper and aluminium sulphate.

The correct answer is A.

Option1 :

Cu and Al2(SO4)3

Option2 :

CuO and Al2(SO4)3

Option3 :

Cu, Al2S3 and SO2

Option4 :

CuO, Al2S3 and SO2

Question 6:

Use the following information to answer the next question.

Barium chloride reacts with sodium sulphate to produce barium sulphate and sodium chloride.

Which of the following chemical equations represents a complete balanced chemical equation for the given process?

Solution :

In a balanced chemical equation, the number of atoms of every element on both the sides of the equation must be equal. Among the given alternatives, the equation given in alternative A, represents a complete balanced chemical equation of the given process as the number of atoms of barium, chlorine, sodium, sulphur, and oxygen on both the sides of the equation are equal.

  BaCl2 aq   +     Na2SO4 aq  →    BaSO4 s  +   2NaCl aqBarium chloride  Sodium sulphate  Barium sulphate  Sodium chloride

The given table shows the number of atoms of each element on the reactant and product sides of the chemical equation.

Elements	Number of atoms in reactants	Number of atoms in products
Ba	1	1
Cl	2	2
Na	2	2
S	1	1
O	4	4

Hence, the equation given in alternative A represents the balanced chemical equation for the given reaction.

Hence, the correct answer is option A.

Option1 :

BaCl2 aq + Na2SO4 aq →BaSO4 s+ 2NaCl aq

Option2 :

BaCl2 aq + Na2SO4 aq →2BaSO4 s+ 2NaCl aq

Option3 :

2BaCl2 aq + Na2SO4 aq →2BaSO4 s+ NaCl aq

Option4 :

2BaCl2 aq + Na2SO4 aq →BaSO4 s+ NaCl aq

Option5 :

Question 7:

Use the following information to answer the next question.

Iron (Fe (s)) reacts with steam (H2O (l)) to produce iron (II, III) oxide (Fe2O3 (s)) and hydrogen gas (H2 (g)). The balanced chemical equation for the given reaction is

Which alternative contains the correct values of the coefficients for the given equation?

Solution :

A balanced chemical equation must have an equal number of atoms of all elements involved in the reaction on both sides of the equation.

The balanced chemical equation for the given reaction is written below.

3Fe �+ 4H2O �→Fe2O3 � +4H2 �Iron          Water      Ferric oxide   Hydogen 

As the numbers of carbon, oxygen, and hydrogen atoms are equal on both sides of the equation, it is a balanced chemical equation.

Hence, the coefficients of Fe, H2O, Fe3O4, and H2 in the given balanced chemical equation are 3, 4, 1, and 4 respectively.

Hence, the correct answer is option D.

Option1 :

i	ii	iii	iv
4	1	2	2

Option2 :

i	ii	iii	iv
1	3	2	3

Option3 :

i	ii	iii	iv
3	2	1	4

Option4 :

i	ii	iii	iv
3	4	1	4

Option5 :

Question 8:

Use the following information to answer the next question.

On heating calcium carbonate, calcium oxide and carbon dioxide are produced. It is an example of reaction and the process is in nature.

The information in which alternative completes the given statement?

Solution :

Calcium carbonate (CaCO3) decomposes on heating, to produce calcium oxide (CaO) and carbon dioxide (CO2). Since a single reactant breaks down to give two simpler products, therefore it is a decomposition reaction. Decomposition of calcium carbonate is carried out by heating. So, it is called thermal decomposition. The chemical equation involved in the reaction is given below.

       CaCO3 s     →Heat   CaO s     +    CO2 gCalcium carbonate      Calcium oxide     Carbon dioxide

The reactions in which energy is absorbed are known as endothermic reactions. Since heat has to be applied in order to decompose calcium carbonate, therefore it is an endothermic reaction.

Hence, the correct answer is option A.

Option1 :

i	ii
decomposition	endothermic

Option2 :

i	ii
combination	endothermic

Option3 :

i	ii
decomposition	exothermic

Option4 :

i	ii
combination	exothermic

Option5 :

Question 9:

Which of the following metals cannot displace copper from copper sulphate solution?

Solution :

In a displacement reaction, a more reactive element displaces a less reactive element from the compound of the latter. Some metals are arranged in the decreasing order of their reactivities as given below.

Zinc > Iron > Lead > Copper > Silver > Gold

Gold is less reactive than copper. Hence, it cannot displace copper from copper sulphate solution.

Hence, the correct answer is option C.

Option1 :

Fe

Option2 :

Zn

Option3 :

Au

Option4 :

Pb

Option5 :

Question 10:

Use the following information to answer the next question.

Ferric oxide reacts with aluminium to produce aluminium oxide and iron. The balanced chemical equation for the given reaction is   Fe2O3 s    +     2Al s     →     Al2O3 s     + 2Fe sFerric oxide      Aluminium      Aluminium oxide    Iron

Which of the following substances is oxidized in the given reaction?

Solution :

The given reaction is an example of a redox reaction. In a redox reaction, the substance that either gains oxygen or loses hydrogen is said to be oxidised and the substance that loses oxygen or gains hydrogen, is said to be reduced.

In the given reaction, aluminium (Al) gains oxygen to form aluminium oxide (Al2O3). Hence, Al is oxidised in the given reaction.

Hence, the correct answer is option C.

Option1 :

Al2O3

Option2 :

Fe2O3

Option3 :

Al

Option4 :

Fe

Option5 :

Question 11:

Which of the following reactions represents a double displacement reaction?

Solution :

Double displacement reactions are the reactions in which an exchange of ions between the reactants takes place. The given reaction is an example of a double displacement reaction in which an exchange of ions takes place between the two reactants (Na2SO4 and BaCl2). Here, barium chloride reacts with sodium sulphate to produce barium sulphate and sodium chloride.

Na2SO4 aq    +       BaCl2aq     →      2NaCl aq   +    BaSO4 sSodium sulphate  Barium chloride      Sodium chloride     Barium sulphate

Hence, the correct answer is option C.

Option1 :

2FeSO4s→Fe2O3s + SO2g+ SO3g

Option2 :

2PbNO32aq→2PbOs +4NO2g+ O2g

Option3 :

Na2SO4aq + BaCl2aq→2NaClaq +BaSO4s

Option4 :

Zns+ 2AgNO3aq→ZnNO32aq + 2Ags

Option5 :

Question 12:

The heating of lead nitrate is an example of reaction and the burning of magnesium is an example of reaction.

The information in which alternative completes the given statement?

Solution :

In decomposition reactions, a compound breaks down or decomposes to form two or more simpler substances.

Lead nitrate, when heated, decomposes to form lead oxide, nitrogen dioxide, and oxygen. The balanced chemical equation for this thermal decomposition reaction can be written as

2PbNO32 s →Heat2PbO s + 4NO2 g+ O2 gLead nitrate           Lead oxide   Nitrogen dioxide  Oxygen

Hence, the heating of lead nitrate is an example of decomposition reaction.

In combination reactions, two or more substances combine to form a new compound. Only one product is obtained in a combination reaction. Magnesium when burns, combines with air to form magnesium oxide. The chemical equation involved in the reaction can be written as:

  2Mg s  +   O2 g → 2MgO sMagnesium  Oxygen  Magnesium oxide

Hence, burning of magnesium is an example of combination reaction.

Hence, the correct answer is option B.

Option1 :

i	ii
combination	decomposition

Option2 :

i	ii
decomposition	combination

Option3 :

i	ii
combination	displacement

Option4 :

i	ii
displacement	decomposition

Option5 :

Question 13:

What are the products obtained when potassium sulphate reacts with barium iodide in an aqueous medium?

Solution :

The given reaction is an example of a double displacement reaction in which an exchange of ions takes place between the two reactants. Here, potassium sulphate and barium iodide react to give potassium iodide and barium sulphate as the products. The chemical equation involved in the reaction can be represented as

       K2SO4 aq    +     BaI2 aq    →        2KI aq     +     BaSO4 sPotassium sulphate   Barium iodide   Potassium iodide  Barium sulphate

Hence, the correct answer is option A.

Option1 :

KI and BaSO4

Option2 :

KI, Ba and SO2

Option3 :

K, I2 and BaSO4

Option4 :

K, Ba, I2 and SO2

Option5 :

Question 14:

Which of the following reactions represents a combination reaction?

Solution :

In a combination reaction, two or more substances combine to form a new compound. Only one product is obtained in a combination reaction. Calcium oxide reacts with water to form calcium hydroxide. Therefore, it is a combination reaction. The chemical equation involved in this reaction can be represented as given below.

CaO s     +     H2O l    →    Ca(OH)2 aqCalcium oxide   Water        Calcium hydroxide

Hence, the correct answer is option A.

Option1 :

CaO s + H2O l→Ca(OH)2 aq

Option2 :

CaCO3 s→CaO s + CO2 g

Option3 :

Zn s+ CuSO4 aq→ZnSO4 aq+ Cu s

Option4 :

2FeSO4 s→Fe2O3 s + SO2 g+ SO3 g

Option5 :

Question 15:

Use the following information to answer the next question.

Some metals are arranged in decreasing order of their reactivities as given below. Magnesium > Zinc > Iron > Lead > Copper > Silver > Gold

Which of the following metals can displace iron from iron sulphate solution?

Solution :

A more reactive element displaces a less reactive element from the compound of the latter.

Zinc (Zn) is more reactive than iron (Fe) and therefore, it can displace iron from iron sulphate solution. The chemical equation involved in the reaction can be represented as:

Zn s + FeSO4 aq→ZnSO4 aq + Fe sZinc      Iron sulphate    Zinc sulphate    Iron

Hence, the correct answer is option D.

Option1 :

Ag

Option2 :

Cu

Option3 :

Pb

Option4 :

Zn

Option5 :

Question 16:

Use the following information to answer the next question.

Magnesium nitride is produced by burning magnesium metal in a pure nitrogen atmosphere.

Which equation correctly represents the activity described in the given statement?

Solution :

In a balanced chemical equation, the number of atoms of every element on both the sides of the equation must be equal. Also, the physical states of the reactants and products must be mentioned. The equation given in alternative C represents the balanced chemical equation for the given process.

The given table shows the number of atoms of each element on both sides.

Elements	Number of atoms on the reactant side	Number of atoms on the product side
Nitrogen	2	2
Magnesium	3	3

Hence, the balanced chemical equation for the given reaction can be written as

    3Mg s   +   N2 g  →  Mg3N2 sMagnesium   Nitrogen   Magnesium nitride

Hence, the correct answer is option C.

Option1 :

Mg3N2 s→3Mg s + N2 g

Option2 :

Mg s + N2 g →Mg3N2 s

Option3 :

3Mg s + N2 g →Mg3N2 (s)

Option4 :

 Mg3N2 (s)→3Mg s + N2 g

Option5 :

Question 17:

Use the following information to answer the next question.

Ammonia gas is produced during the reaction of nitrogen with hydrogen.

The balanced chemical equation for the given reaction is

Solution :

A balanced equation is one that follows the law of conservation of mass, that is, the number of atoms of elements on the reactant side is equal to the number of atoms of elements on the product side.

For the reaction

  N2 g +  3H2 g → 2NH3 gNitrogen  Hydrogen  Ammonia

Reactant side: Number of nitrogen atoms = 2

Number of hydrogen atoms = 6

Product side: Number of nitrogen atoms = 2

Number of hydrogen atoms = 6

Thus, the numbers of hydrogen and nitrogen atoms are equal on both the reactant and product sides. Hence, the given equation is balanced.

Hence, the correct answer is option C.

Option1 :

N2 g +  H2 g → 2NH3 g

Option2 :

2N2 g +  H2 g → 2NH3 g

Option3 :

N2 g +  3H2 g → 2NH3 g

Option4 :

2N2 g +  3H2 g → 2NH3 g

Option5 :

Question 18:

Use the following information to answer the next question.

When hydrogen gas (H2) is passed over copper oxide (CuO), copper (Cu) is produced along with water (H2O). The balanced chemical equation for the given reaction is     CuOs    +    H2 g   →Heat  Cu s  +  H2O lCopper oxide   Hydrogen           Copper        Water

Which substance is oxidised in the given reaction?

Solution :

The given reaction is an example of a redox reaction. In such a reaction, if a substance gains oxygen or loses hydrogen, it is said to be oxidized and if a substance loses oxygen or gains hydrogen during the reaction, it is said to be reduced. In the given reaction, hydrogen gains oxygen to form water and copper oxide loses oxygen to form copper.

Hence, H2 is oxidised and CuO is reduced in the given reaction.

Hence, the correct answer is option A.

Option1 :

H2

Option2 :

Cu

Option3 :

H2O

Option4 :

CuO

Option5 :

Question 19:

Potassium hydroxide reacts with sulphuric acid to produce potassium sulphate and water.

Which equation represents the correct word equation for the given reaction?

Solution :

While writing the word equation of a chemical reaction, the reactants are written on the left-hand side with a plus (+) sign between them and the products are written on the right-hand side with a plus (+) sign. An arrowhead (→) points toward the products, and shows the direction of the reaction.

In the given reaction, potassium hydroxide reacts with sulphuric acid to produce potassium sulphate and water. Hence, in the given reaction potassium hydroxide and sulphuric acid are the reactants and potassium sulphate and water are the products. Hence, the correct word equation of the given reaction can be written as

Potassium hydroxide + Sulphuric acid → Potassium sulphate + Water

Hence, the correct answer is option C.

Option1 :

Potassium hydroxide − Sulphuric acid → Potassium sulphate − Water

Option2 :

Potassium hydroxide + Sulphuric acid Potassium sulphate + Water

Option3 :

Potassium hydroxide + Sulphuric acid → Potassium sulphate + Water

Option4 :

Potassium hydroxide − Sulphuric acid Potassium sulphate − Water

Option5 :

Question 20:

Use the following information to answer the next question.

White silver chloride changes to grey in sunlight because of the formation of precipitation of silver along with the evolution of chlorine gas.

Which of the following chemical equations represents a complete balanced chemical equation for the given activity?

Solution :

In a balanced chemical equation, the number of atoms of every element on both the sides of the equation must be equal. Further, the reaction condition and the physical states of the reactants and the products are mentioned along with their chemical formulae. Among the given alternatives, the equation given in alternative A represents the balanced chemical equation for the given process.

2AgCl s  →Sunlight2Ag s + Cl2 gSilver chloride         Silver         Chlorine

Hence, the correct answer is option A.

Option1 :

2AgCl s  →Sunlight2Ag s + Cl2 g

Option2 :

Ag s + Cl2 g →Sunlight2AgCl s

Option3 :

AgCl s  →SunlightAg s + Cl2 g

Option4 :

Ag s + Cl2 g→Sunlight2AgCl s  

Option5 :

Question 21:

Zinc reacts with ferrous sulphate to produce

Solution :

The given reaction is an example of a displacement reaction. As zinc is more reactive than iron, it replaces iron from an iron sulphate solution to give iron and zinc sulphate. The chemical equation involved in the reaction can be written as

Zn s + FeSO4 aq→ZnSO4 aq+ Fe sZinc    Iron sulphate    Zinc sulphate   Iron

The correct answer is A.

Option1 :

ZnSO4 and Fe

Option2 :

ZnO, O2 and Fe

Option3 :

ZnO and Fe2S3

Option4 :

FeS, SO2 and ZnO

Option5 :

Question 22:

Which of the following chemical reactions is an example of a combination reaction?

Solution :

A combination reaction is defined as one in which two or more reactants unite to form a single product. In the given reaction, sulphur combines with oxygen to form a single product, sulphur trioxide.

 2S s  + 3O2 g  → 2SO3 gSulphur  Oxygen  Sulphur trioxide

Hence, the correct answer is option C.

Option1 :

Ca s+ 2HCl aq→CaCl2 aq+ H2 g

Option2 :

2KClO3 s→2KCl s+ 3O2 g

Option3 :

2S s +3O2 g →2SO3 g

Option4 :

2H2O aq →2H2 g + O2 g

Option5 :

Question 23:

An example of a double displacement reaction is

Solution :

In a double displacement reaction, the anions and cations of two different molecules switch places, forming two entirely different compounds. In the given reaction,  the anions are and  and  the cations are and  .  They exchange places to form and

Fe2(SO4)3 aq    +   6KOH aq    →    2Fe(OH)3 aq  +   3K2SO4 aqFerric sulphate  Potassium hydroxide  Ferric hydroxide  Potassium sulphate ,

Hence, the correct answer is option D.

Option1 :

Option2 :

Option3 :

Option4 :

Option5 :

Question 24:

Use the following information to answer the next question.

When copper turnings are added to a clear solution of silver nitrate, a greyish deposit of silver is observed after some time. Silver gets precipitated and copper (II) nitrate is also formed. The reaction is an example of reaction and is more reactive than.

The information in which alternative completes the given statement?

Solution :

The chemical equation for the reaction is

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

In the given reaction, a metal (copper) is replacing another metal (silver) from the solution of its compound. Hence, the given reaction is an example of a displacement reaction.

Copper replaces silver from the solution of its compound. Hence, copper is more reactive than silver.

Hence, the correct answer is option A.

Option1 :

i	ii	iii
displacement	copper	silver

Option2 :

i	ii	iii
decomposition	copper	silver

Option3 :

i	ii	iii
decomposition	silver	copper

Option4 :

i	ii	iii
displacement	silver	copper

Option5 :

Question 25:

Corrosion and rancidity are the result of reaction of iron articles and oils/fats respectively. Galvanization is done to prevent corrosion of iron articles and are used to prevent rancidity of oils or fats.

The information in which alternative completes the given statements?

Solution :

Corrosion of iron is a result of reaction of iron with oxygen and moisture. It is an example of oxidation reaction. This leads to the formation of a reddish-brown coating on iron articles.

Rancidity is caused by the oxidation of fats, oils, and lipids present in food materials causing them to smell foul and taste bad.

Galvanisation is used to prevent corrosion, while anti-oxidants are added to food materials to avoid rancidity.

Hence, the correct answer is option D.

Option1 :

(i) displacement, (ii) oxidants

Option2 :

(i) oxidation, (ii) oxidants

Option3 :

(i) displacement, (ii) anti-oxidants

Option4 :

(i) oxidation, (ii) anti-oxidants

Option5 :