Chemical Reactions and Equations Test

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Chemical Reactions and Equations Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride. This is a :

A
decomposition reaction

B
combination reaction

C
displacement reaction

D
double displacement reaction

Solution

Reaction of magnesium with nitrogen is a combination reaction as these two reactants ( $$Mg$$ and $$N_{2}$$) combine together to form a single product as magnesium nitride ($$Mg_{3}N_{2}$$). The equation can be written as:

$$3Mg(s) + N_{2}(g) \rightarrow Mg_{3}N_{2}(s)$$
Question 2
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Which of the following is/are combination reaction(s)?
(i) $$2KClO_{3} \overset{Heat}{\rightarrow} 2KCl + 3O_{2}$$
(ii) $$MgO + H_{2}O \rightarrow Mg(OH)_{2}$$
(iii) $$4Al + 3O_{2} \rightarrow 2Al_{2} O_{3}$$
(iv) $$Zn + FeSO_{4} \rightarrow ZnSO_{4} + Fe$$

A
(i) and (iii)

B
(iii) and (iv)

C
(ii) and (iv)

D
(ii) and (iii)

Solution

Option (i) is a decomposition reaction.
Option (ii) is a combination reaction as magnesium oxide $$(MgO)$$ and water combines to form magnesium hydroxide $$(Mg(OH)_{2})$$.
Option (iii) is again a combination reaction as aluminium $$(Al)$$ combines with oxygen $$(O_{2})$$ to form aluminium oxide $$(Al_{2}O_{3})$$.
Option (iv) is a displacement reaction.
The correct answer is option $$D$$.
Question 3
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Which of the following statements about the given reaction is/are correct?
$$3Fe(s) + 4H_{2}O(g) \rightarrow Fe_{3}O_{4}(s) + 4H_{2}(g)$$
(i) Iron metal is getting oxidised.
(ii) Water is getting reduced.
(iii) Water is acting as reducing agent.
(iv) Water is acting as oxidising agent.

A
(i), (ii) and (iii)

B
(iii) and (iv)

C
(i), (ii) and (iv)

D
(ii) and (iv)

Solution

Option (i) is correct as iron (Fe) is combining with oxygen to form iron oxide ($$Fe_3O_4=Fe^{II}O.{ Fe^{III} }_{ 2 }{ O }_{ 3 }$$).
Iron is oxidising from 0 to +2 and +3 state.
Option (ii) is correct as water ($$H_{2}O$$) is being reduced by removal of oxygen to form hydrogen ($$H_{2}$$) gas.

Option (iv) is correct as water ($$ H_{2}O$$) itself is being reduced and is oxidising Iron(Fe), thereby acting as an oxidising agent.

Option C is correct.
Question 4
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If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of:

A
$$CuSO_{4}$$

B
$$CuCO_{3}$$

C
$$Cu(NO_{3})_{2}$$

D
$$CuO$$

Solution

The green coat is due to the basic copper carbonate formation and is a mixture of copper carbonate and copper hydroxide $$(CuCO_3$$ and $$Cu(OH)_2)$$.
Question 5
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Silver articles become black on prolonged exposure to air.
This is due to the formation of :

A
$$Ag_{3}N$$

B
$$Ag_{2}O$$

C
$$Ag_{2}S$$

D
$$Ag_{2}S$$ and $$Ag_{3}N$$

Solution

Silver metal is highly unreactive, i.e., it does not react with oxygen.
But with prolonged exposure to air, it reacts with hydrogen sulphide gas ($$H_2S$$).
Silver articles form a coating of silver sulphide ($$Ag_2S$$) and lose their shine (get tarnished).
Question 6
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On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained. What other name can be given to this precipitation reaction?

A
Synthesis reaction

B
Double displacement reaction

C
Combination reaction

D
Decomposition reaction

Solution

Barium chloride ($$BaCl_{2}$$) reacts with sodium sulphite ($$Na_{2}SO_{3}$$) to form barium sulphite ($$BaSO_{3}$$) and sodium chloride (NaCl).

$$ BaCl_{2}(aq) + Na_{2}SO_{3}(aq) \rightarrow BaSO_{3}(s) + 2NaCl(aq)$$
(white ppt)

The above precipitation reaction is also a double displacement reaction as both reactants exchange their ions to form new products.
Question 7
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Identify the type of chemical reaction.
$$Mg(s) + Cl_{2}(g) \rightarrow MgCl_{2}(s)$$

A
Decomposition reactions

B
Combination reaction

C
Displacement reaction

D
Double displacement reaction

Solution

Magnesium ($$Mg$$) combines with chlorine ($$Cl_{2}$$) to form a new product as magnesium chloride ($$MgCl_{2}$$). Therfore its a combination reaction and the balanced equation can be written as:
$$Mg(s) + Cl_{2}(g) \rightarrow MgCl_{2}(s)$$
Question 8
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$$HgO(s) \xrightarrow{Heat} Hg(l) + O_{2}(g)$$
The above given reaction is:

A
combustion reaction

B
displacement reaction

C
thermal decomposition reaction

D
photolytic decomposition reaction

Solution

Mercuric oxide ($$HgO$$) decomposes on heating to give mercury ($$Hg$$) and oxygen ($$O_{2}$$). It is a thermal decomposition reaction and the balanced equation can be written as:
$$2HgO(s) \overset{heat}{\rightarrow} 2Hg(l) + O_{2}(g)$$
Question 9
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What type of chemical reaction does the reaction belong to?
A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

A
Precipitation Reactions

B
Neutralization Reactions

C
Decomposition Reactions

D
Displacement Reactions

Solution

Sodium metal $$(Na)$$ reacts with ethanol ($$C_{2}H_{5}OH$$) to produce sodium ethoxide ($$C_{2}H_{5}ONa$$) and hydrogen ($$H_{2}$$). It is a displacement reaction in which the more active sodium displaces hydrogen in ethanol. The equation can be written as:
$$2Na + 2C_{2}H_{5}OH \rightarrow 2C_{2}H_{5}ONa + H_{2}$$

Question 10

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Write the balanced chemical equations for the following reactions:

Sodium hydrogen carbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.

$$NaHCO_{3} + 2HCl \rightarrow NaCl + 2H_{2}O + CO_{2}$$

$$2NaHCO_{3} + HCl \rightarrow NaCl + H_{2}O + 2CO_{2}$$

$$NaHCO_{3} + HCl \rightarrow NaCl + H_{2}O + CO_{2}$$

$$2NaHCO_{3} + HCl \rightarrow 2NaCl + H_{2}O + CO_{2}$$

Solution

$$NaHCO_3+HCl\longrightarrow NaCl+H_2O+CO_2$$

	No. of Atom	No. of Atom
$$Na$$	$$1$$	$$1$$
$$H$$	$$2$$	$$2$$
$$C$$	$$1$$	$$1$$
$$Cl$$	$$1$$	$$1$$
$$O$$	$$3$$	$$3$$

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Chemical Reactions and Equations Test - 23

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Chemical Reactions and Equations Test - 23

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Question 1

decomposition reaction

combination reaction

displacement reaction

double displacement reaction

Solution

Question 2

(i) and (iii)

(iii) and (iv)

(ii) and (iv)

(ii) and (iii)

Solution

Question 3

(i), (ii) and (iii)

(iii) and (iv)

(i), (ii) and (iv)

(ii) and (iv)

Solution

Question 4

$$CuSO_{4}$$

$$CuCO_{3}$$

$$Cu(NO_{3})_{2}$$

$$CuO$$

Solution

Question 5

$$Ag_{3}N$$

$$Ag_{2}O$$

$$Ag_{2}S$$

$$Ag_{2}S$$ and $$Ag_{3}N$$

Solution

Question 6

Synthesis reaction

Double displacement reaction

Combination reaction

Decomposition reaction

Solution

Question 7

Decomposition reactions

Combination reaction

Displacement reaction

Double displacement reaction

Solution

Question 8

combustion reaction

displacement reaction

thermal decomposition reaction

photolytic decomposition reaction

Solution

Question 9

Precipitation Reactions

Neutralization Reactions

Decomposition Reactions

Displacement Reactions

Solution

Question 10

$$NaHCO_{3} + 2HCl \rightarrow NaCl + 2H_{2}O + CO_{2}$$

$$2NaHCO_{3} + HCl \rightarrow NaCl + H_{2}O + 2CO_{2}$$

$$NaHCO_{3} + HCl \rightarrow NaCl + H_{2}O + CO_{2}$$

$$2NaHCO_{3} + HCl \rightarrow 2NaCl + H_{2}O + CO_{2}$$

Solution

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