Chemical Reactions and Equations - Case Based Questions

Q 1 :

Read the passage carefully and answer the following questions from (i) to (v):

Equations must always be balanced. The numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
In a combination reaction, two or more substances combine to form a new single substance. In a decomposition reaction, a single substance decomposes to give two or more substances. When an element displaces another element from its compound, a displacement reaction occurs. Reactions also involve gain or loss of oxygen or hydrogen by substances. Oxidation = gain of oxygen or loss of hydrogen. Reduction = loss of oxygen or gain of hydrogen.

(i) Which of the following reactions is not correct?

$Z n + C u S O_{4} \to Z n S O_{4} + C u$
$2 A g + C u {(N O_{3})}_{2} \to 2 A g N O_{3} + C u$
$F e + C u S O_{4} \to F e S O_{4} + C u$
$M g + 2 H C l \to M g C l_{2} + H_{2}$

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(2)

Q 2 :

Read the passage carefully and answer the following questions from (i) to (v):

Equations must always be balanced. The numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
In a combination reaction, two or more substances combine to form a new single substance. In a decomposition reaction, a single substance decomposes to give two or more substances. When an element displaces another element from its compound, a displacement reaction occurs. Reactions also involve gain or loss of oxygen or hydrogen by substances. Oxidation = gain of oxygen or loss of hydrogen. Reduction = loss of oxygen or gain of hydrogen.

(ii) Which of the following is not a displacement reaction?

Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Aluminium + Copper chloride → Aluminium chloride + Copper
Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)

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(1)

Q 3 :

Read the passage carefully and answer the following questions from (i) to (v):

Equations must always be balanced. The numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
In a combination reaction, two or more substances combine to form a new single substance. In a decomposition reaction, a single substance decomposes to give two or more substances. When an element displaces another element from its compound, a displacement reaction occurs. Reactions also involve gain or loss of oxygen or hydrogen by substances. Oxidation = gain of oxygen or loss of hydrogen. Reduction = loss of oxygen or gain of hydrogen.

(iii) Identify the correct chemical reaction.

Hydrogen sulphide gas burns in air to give water and sulphur.
Potassium metal reacts with water to give potassium hydroxide and water.
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Zinc reacts with silver nitrate to form zinc nitrite and silver.

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(3)

Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

Q 4 :

Read the passage carefully and answer the following questions from (i) to (v):

Equations must always be balanced. The numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
In a combination reaction, two or more substances combine to form a new single substance. In a decomposition reaction, a single substance decomposes to give two or more substances. When an element displaces another element from its compound, a displacement reaction occurs. Reactions also involve gain or loss of oxygen or hydrogen by substances. Oxidation = gain of oxygen or loss of hydrogen. Reduction = loss of oxygen or gain of hydrogen.

(iv) Which of the following reactions will evolve hydrogen gas with a pop sound?

Concentrated nitric acid is reacted with sulphur.
A small piece of zinc is added to dilute hydrochloric acid.
Ammonia is passed over heated copper (II) oxide.
Lead nitrate is heated strongly in a test tube.

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(2)

A small piece of zinc is added to dilute hydrochloric acid.

Q 5 :

Read the passage carefully and answer the following questions from (i) to (v):

Equations must always be balanced. The numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
In a combination reaction, two or more substances combine to form a new single substance. In a decomposition reaction, a single substance decomposes to give two or more substances. When an element displaces another element from its compound, a displacement reaction occurs. Reactions also involve gain or loss of oxygen or hydrogen by substances. Oxidation = gain of oxygen or loss of hydrogen. Reduction = loss of oxygen or gain of hydrogen.

(v) Identify the type of reaction in the following:

$F e + C u S O_{4} (a q) ⟶ F e S O_{4} (a q) + C u (s)$

Oxidation Reaction
Redox Reaction
Combustion Reaction
None of these

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Redox Reaction

Q 6 :

Read the passage carefully and answer the following questions from (i) to (v):

Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.

(i) Which of the following equation are balanced?

$3 F e (s) + 4 H_{2} O (g) \to F e_{3} O_{4} (s) + 4 H_{2} (g)$
$2 C a O (s) + H_{2} O (l) \to 2 C a {(O H)}_{2} (a q)$
$C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (g)$
$2 A g B r (s) \to A g (s) + 2 B r_{2} (g)$

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(1)

Q 7 :

Read the passage carefully and answer the following questions from (i) to (v):

Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.

(ii) The following represent the exothermic reaction. The reactants react to form product, with the release of energy in the form of heat

Which of the following involve an exothermic reaction?

Respiration
Oxidation
Combustion
All of these

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(4)

Q 8 :

Read the passage carefully and answer the following questions from (i) to (v):

Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.

(iii) When the powder of a common metal is heated in an open china dish, its colour turns black. However, when hydrogen is passed over the hot black substance so formed, it regains its original colour. What type of chemical reaction takes place in each of the two given steps?

First oxidation reaction then displacement reaction
First combustion reaction, then reduction reaction
First oxidation reaction, then redox reaction
First reduction reaction, then redox reaction

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First oxidation reaction, then redox reaction

Q 9 :

Read the passage carefully and answer the following questions from (i) to (v):

Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.

(iv) Study the given diagram in which white powder of silver chloride was left open in sunlight. After few hours, it was observed that the white powder changed to silvery material. What type of reaction is it?

Displacement reaction
Decomposition reaction
Decomposition reaction
Corrosion

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Decomposition reaction

Q 10 :

Read the passage carefully and answer the following questions from (i) to (v):

Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical reaction.

(v) After rain, Shreya observed that an iron lock developed a reddish-brown powdery covering after rain. She cleaned it with sandpaper and found a shiny layer beneath. What could she do to prevent such corrosion from occurring again?

To buy a new similar lock
To coat the surface with a layer of paint
To clean the lock using sandpaper regularly
To buy a gold lock instead of an iron lock

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To coat the surface with a layer of paint

Q 11 :

Read the passage carefully and answer the following questions from (i) to (v):

Situations of daily life can be represented by equations in few variables. In the same way, chemical reactions can be represented with the help of symbols of elements and formulae of the substances involved. This method of writing a reaction is known as a chemical equation. The substances which combine to react are known as reactants and new substances produced are known as products. An unbalanced chemical equation needs to be balanced which means that an equal number of atoms of different elements are present in the reactant as well as in the product side. Most importantly, the formulae of the compounds are not altered while balancing the equation.

(i) Chemical equations balancing is in accordance with:

Law of constant proportions
Law of constant proportions
Law of conservation of mass
Both a and c

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Law of conservation of mass

Q 12 :

Read the passage carefully and answer the following questions from (i) to (v):

Situations of daily life can be represented by equations in few variables. In the same way, chemical reactions can be represented with the help of symbols of elements and formulae of the substances involved. This method of writing a reaction is known as a chemical equation. The substances which combine to react are known as reactants and new substances produced are known as products. An unbalanced chemical equation needs to be balanced which means that an equal number of atoms of different elements are present in the reactant as well as in the product side. Most importantly, the formulae of the compounds are not altered while balancing the equation.

(ii) The chemical equation which is unbalanced is:

$2 N a H C O_{3} ⟶ N a_{2} C O_{3} + H_{2} O + C O_{2}$
$2 C_{4} H_{10} + 12 O_{2} ⟶ 8 C O_{2} + 10 H_{2} O$
$A l + 6 H_{2} O ⟶ 2 A l {(O H)}_{3} + 3 H_{2}$
$4 N H_{3} + 5 O_{2} ⟶ 4 N O + 6 H_{2} O$

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(2)

Q 13 :

Read the passage carefully and answer the following questions from (i) to (v):

Situations of daily life can be represented by equations in few variables. In the same way, chemical reactions can be represented with the help of symbols of elements and formulae of the substances involved. This method of writing a reaction is known as a chemical equation. The substances which combine to react are known as reactants and new substances produced are known as products. An unbalanced chemical equation needs to be balanced which means that an equal number of atoms of different elements are present in the reactant as well as in the product side. Most importantly, the formulae of the compounds are not altered while balancing the equation.

(iii) In the given balanced equation, the coefficients a, b, c, d respectively are:

$a M g_{3} N_{2} + b H_{2} O ⟶ c M g {(O H)}_{2} + d N H_{3}$

1, 3, 3, 2
1, 6, 3, 2
1, 2, 3, 2
2, 3, 6, 2

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1, 6, 3, 2

Q 14 :

Read the passage carefully and answer the following questions from (i) to (v):

Situations of daily life can be represented by equations in few variables. In the same way, chemical reactions can be represented with the help of symbols of elements and formulae of the substances involved. This method of writing a reaction is known as a chemical equation. The substances which combine to react are known as reactants and new substances produced are known as products. An unbalanced chemical equation needs to be balanced which means that an equal number of atoms of different elements are present in the reactant as well as in the product side. Most importantly, the formulae of the compounds are not altered while balancing the equation.

**(iv) Which of the following is not conveyed by a balanced chemical equation?**

If a particular reaction is practically feasible or not.
Symbols and formulae of all the reactants.
Number of atoms and molecules of the products formed.
The physical state of reactants and products.

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If a particular reaction is practically feasible or not.

Q 15 :

Read the passage carefully and answer the following questions from (i) to (v):

Situations of daily life can be represented by equations in few variables. In the same way, chemical reactions can be represented with the help of symbols of elements and formulae of the substances involved. This method of writing a reaction is known as a chemical equation. The substances which combine to react are known as reactants and new substances produced are known as products. An unbalanced chemical equation needs to be balanced which means that an equal number of atoms of different elements are present in the reactant as well as in the product side. Most importantly, the formulae of the compounds are not altered while balancing the equation.

(v) Which of the following is true for an unbalanced chemical equation?

The number of atoms is more on the right side of the equation
The number of atoms is less on the left side of the equation
The number of atoms is equal on both sides of the equation
Both (a) and (b)

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Both (a) and (b)

Q 16 :

Read the passage carefully and answer the following questions from (i) to (v):

When two or more reactants combine to form a single product, the reaction is named a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature. A lot of heat is produced during the reaction.

$C a O + H_{2} O \to C a {(O H)}_{2} + H e a t$
Calcium oxide + Water → Calcium hydroxide

Solution of calcium hydroxide is used to white-wash walls. It reacts slowly with carbon dioxide present in the air to form a thin layer of carbonate which gives a shiny appearance.

(i) The chemical name of quick lime is:

Calcium oxide
Calcium oxide
Calcium hydroxide
Carbon dioxide

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Calcium oxide

Q 17 :

Read the passage carefully and answer the following questions from (i) to (v):

When two or more reactants combine to form a single product, the reaction is named a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature. A lot of heat is produced during the reaction.

$C a O space plus space H subscript 2 O space rightwards arrow space C a left parenthesis O H right parenthesis subscript 2 space plus space H e a t$
Calcium oxide + Water → Calcium hydroxide
Solution of calcium hydroxide is used to white-wash walls. It reacts slowly with carbon dioxide present in the air to form a thin layer of carbonate which gives a shiny appearance.

(ii) On passing carbon dioxide through lime water:

Calcium hydroxide is formed
A white precipitate of CaO is formed
Lime water turns milky
Colour of lime water turns green

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Lime water turns milky

Q 18 :

Read the passage carefully and answer the following questions from (i) to (v):

When two or more reactants combine to form a single product, the reaction is named a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature. A lot of heat is produced during the reaction.

$C a O space plus space H subscript 2 O space rightwards arrow space C a left parenthesis O H right parenthesis subscript 2 space plus space H e a t$
Calcium oxide + Water → Calcium hydroxide

Solution of calcium hydroxide is used to white-wash walls. It reacts slowly with carbon dioxide present in the air to form a thin layer of carbonate which gives a shiny appearance.

(iii) Following observations were recorded when calcium oxide reacts vigorously with water. Identify the incorrect observations:

I. It is an endothermic reaction
II. Slaked lime is produced
III. Quick lime is produced
IV. It is an exothermic reaction

I and II
III and IV
I and III
II and IV

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I and III

Q 19 :

Read the passage carefully and answer the following questions from (i) to (v):

When two or more reactants combine to form a single product, the reaction is named a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature. A lot of heat is produced during the reaction.

$C a O space plus space H subscript 2 O space rightwards arrow space C a left parenthesis O H right parenthesis subscript 2 space plus space H e a t$
Calcium oxide + Water → Calcium hydroxide

Solution of calcium hydroxide is used to white-wash walls. It reacts slowly with carbon dioxide present in the air to form a thin layer of carbonate which gives a shiny appearance.

(iv) Quick lime combines vigorously with water to form Y which reacts slowly with carbon dioxide in the air to form Z.

[Y] - Calcium carbonate, [Z] - Calcium hydroxide
[Y] - Calcium hydroxide, [Z] - Calcium carbonate
[Y] - Calcium , [Z] - Calcium bicarbonate
[Y] - Calcium bicarbonate , [Z] - Calcium metal

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(2)

Q 20 :

Read the passage carefully and answer the following questions from (i) to (v):

When two or more reactants combine to form a single product, the reaction is named a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature. A lot of heat is produced during the reaction.

$C a O space plus space H subscript 2 O space rightwards arrow space C a left parenthesis O H right parenthesis subscript 2 space plus space H e a t$
Calcium oxide + Water → Calcium hydroxide

Solution of calcium hydroxide is used to white-wash walls. It reacts slowly with carbon dioxide present in the air to form a thin layer of carbonate which gives a shiny appearance.

(v) Which of the following is an endothermic reaction?

Combination of carbon and oxygen to form carbon monoxide
Combination of nitrogen and oxygen to form nitrogen monoxide
Combination of glucose and oxygen to form carbon dioxide and water
Combination of zinc and hydrochloric acid to form zinc chloride and hydrogen

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Combination of nitrogen and oxygen to form nitrogen monoxide

Q 21 :

Read the passage carefully and answer the following questions from (i) to (v):

A decomposition reaction is opposite to a combination reaction. A single reactant breaks down to form two or more products in a decomposition reaction. Thermal decomposition reaction uses energy in the form of heat to decompose reactants. Electrolytic decomposition reaction involves the use of electrical energy to break reactant molecules. Photolysis or photochemical decomposition involves the use of light energy.

(i) Name the component of our diet, decomposition of which produces the amino acid:

Starch
Protein
Carbohydrate
Fat

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Protein

Q 22 :

Read the passage carefully and answer the following questions from (i) to (v):

A decomposition reaction is opposite to a combination reaction. A single reactant breaks down to form two or more products in a decomposition reaction. Thermal decomposition reaction uses energy in the form of heat to decompose reactants. Electrolytic decomposition reaction involves the use of electrical energy to break reactant molecules. Photolysis or photochemical decomposition involves the use of light energy.

(ii) Silver chloride (AgCl) when exposed to sunlight for a long duration turns grey. Consider the following statements:
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

Only I
Only I and II
Only II and III
Only IV

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Only I

Q 23 :

Read the passage carefully and answer the following questions from (i) to (v):

A decomposition reaction is opposite to a combination reaction. A single reactant breaks down to form two or more products in a decomposition reaction. Thermal decomposition reaction uses energy in the form of heat to decompose reactants. Electrolytic decomposition reaction involves the use of electrical energy to break reactant molecules. Photolysis or photochemical decomposition involves the use of light energy.

(iii) Which of the following is a decomposition reaction?

$N a O H + H C l ⟶ N a C l + H_{2} O$
$N H_{4} C N O ⟶ H_{2} N C O N H_{2}$
$2 K C l O_{3} ⟶ 2 K C l + 3 O_{2}$
$H_{2} + I_{2} ⟶ 2 H I$

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Q 24 :

Read the passage carefully and answer the following questions from (i) to (v):

A decomposition reaction is opposite to a combination reaction. A single reactant breaks down to form two or more products in a decomposition reaction. Thermal decomposition reaction uses energy in the form of heat to decompose reactants. Electrolytic decomposition reaction involves the use of electrical energy to break reactant molecules. Photolysis or photochemical decomposition involves the use of light energy.

(iv) $2 P b {(N O_{3})}_{2} \to 2 P b O + n A + O_{2}$
What is nA in the given reaction?

4NO
$4 N O_{2}$
$2 P b N O_{2}$
$N O_{2}$

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(2)

Q 25 :

Read the passage carefully and answer the following questions from (i) to (v):

A decomposition reaction is opposite to a combination reaction. A single reactant breaks down to form two or more products in a decomposition reaction. Thermal decomposition reaction uses energy in the form of heat to decompose reactants. Electrolytic decomposition reaction involves the use of electrical energy to break reactant molecules. Photolysis or photochemical decomposition involves the use of light energy.

(v) When electricity is passed through water, what kind of reaction takes place?

Thermal decomposition
Electrolytic decomposition
Photochemical decomposition
Displacement reaction

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Electrolytic decomposition

Q 26 :

Read the passage carefully and answer the following questions from (i) to (v):

During a chemical reaction, it is possible that one element takes the place of another element in a compound. Such reactions are called displacement reactions. Precisely, an element that is high in the Reactivity series displaces an element that is lower in the reactivity series. In single displacement reactions, only one element displaces the other element from its compound. The displacement reaction between iron(III) oxide and powdered aluminum produces so much heat that iron gets into its molten state

(i) Copper displaces which of the following metals from its salt solution?

$Z n S O_{4}$
$F e S O_{4}$
$A g N O_{3}$
$N i S O_{4}$

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(3)

Q 27 :

Read the passage carefully and answer the following questions from (i) to (v):

During a chemical reaction, it is possible that one element takes the place of another element in a compound. Such reactions are called displacement reactions. Precisely, an element that is high in the Reactivity series displaces an element that is lower in the reactivity series. In single displacement reactions, only one element displaces the other element from its compound. The displacement reaction between iron(III) oxide and powdered aluminum produces so much heat that iron gets into its molten state

(ii) Characteristic of the gas evolved during the reaction of zinc with dilute sulphuric acid is:

Green in colour having a foul smell
Green in colour having a foul smell
Red in colour having a sweet smell
Colourless, pungent-smelling and burns with a pop sound

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Q 28 :

Read the passage carefully and answer the following questions from (i) to (v):

During a chemical reaction, it is possible that one element takes the place of another element in a compound. Such reactions are called displacement reactions. Precisely, an element that is high in the Reactivity series displaces an element that is lower in the reactivity series. In single displacement reactions, only one element displaces the other element from its compound. The displacement reaction between iron(III) oxide and powdered aluminum produces so much heat that iron gets into its molten state

(iii) A reddish-brown residue is obtained when dry hydrogen is passed over a heated oxide of metal M. This residue could be:

Lead
Silver
Copper
Zinc

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Copper

Q 29 :

Read the passage carefully and answer the following questions from (i) to (v):

During a chemical reaction, it is possible that one element takes the place of another element in a compound. Such reactions are called displacement reactions. Precisely, an element that is high in the Reactivity series displaces an element that is lower in the reactivity series. In single displacement reactions, only one element displaces the other element from its compound. The displacement reaction between iron(III) oxide and powdered aluminum produces so much heat that iron gets into its molten state

(iv) Which among the following is a displacement reaction?

$C a O + H_{2} O ⟶ C a {(O H)}_{2}$
$M g C O_{3} ⟶ M g + C O_{2}$
$M g + C u S O_{4} ⟶ M g S O_{4} + C u$
$H_{2} + C l_{2} ⟶ 2 H C l$

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Q 30 :

Read the passage carefully and answer the following questions from (i) to (v):

During a chemical reaction, it is possible that one element takes the place of another element in a compound. Such reactions are called displacement reactions. Precisely, an element that is high in the Reactivity series displaces an element that is lower in the reactivity series. In single displacement reactions, only one element displaces the other element from its compound. The displacement reaction between iron(III) oxide and powdered aluminum produces so much heat that iron gets into its molten state

(v) Which is the correct observation for the reaction between granulated zinc and dilute hydrochloric acid?

The reaction mixture turns milky.
Greenish-yellow gas is evolved.
The colourless and odourless gas evolves with a pop sound.
The surface of the metal turns shining.

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colourless and odourless gas evolves with a pop sound

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