Types of Chemical Reactions Questions in English

(A) When a piece of $Zn$ metal is added to $CuSO_4$ solution, a displacement reaction occurs because $Zn$ is more reactive than $Cu$.
$Zn$ displaces $Cu$ from its solution.
$Zn(s) + CuSO_4(aq) \text{ (Blue colour)} \longrightarrow ZnSO_4(aq) \text{ (Colourless)} + Cu(s)$

(N/A) $(i)$ Combination reaction: In this reaction,two or more reactants combine to form a single product. Here,calcium oxide $(CaO)$ reacts with carbon dioxide $(CO_2)$ to form a single product,calcium carbonate $(CaCO_3)$.
$(ii)$ Displacement reaction: In this reaction,a more reactive element displaces a less reactive element from its compound. Here,sodium $(Na)$ displaces hydrogen from water $(H_2O)$ to form sodium hydroxide $(NaOH)$ and releases hydrogen gas $(H_2)$.

(N/A) $(i)$ Displacement reaction: $A$ more reactive metal $(Mg)$ displaces a less reactive metal $(Cu)$ from its salt solution $(CuSO_4)$.
$(ii)$ Decomposition reaction: $A$ single compound $(NH_4NO_2)$ breaks down into two or more simpler substances ($N_2$ and $H_2O$).

(N/A) The given reaction is a $Double \ Displacement \ Reaction$.
In a double displacement reaction, two reactant compounds exchange their ions to form two new compounds.
In this specific reaction, the $Cu^{2+}$ ion from copper sulfate exchanges with the $Na^{+}$ ion from sodium hydroxide to form copper hydroxide $(Cu(OH)_{2})$ and sodium sulfate $(Na_{2}SO_{4})$.

(N/A) When white silver chloride $(AgCl)$ is exposed to sunlight,it undergoes a photochemical decomposition reaction.
In this process,silver chloride decomposes into metallic silver $(Ag)$ and chlorine gas $(Cl_2)$.
The chemical equation for this reaction is: $2AgCl(s) \xrightarrow{\text{sunlight}} 2Ag(s) + Cl_2(g)$.
The grey colour is due to the formation of metallic silver,which is grey in appearance.

(N/A) In a decomposition reaction,a single substance [compound] breaks down to produce two or more simpler substances [elements or compounds].
Conversely,in a combination reaction,two or more substances [elements or compounds] combine to form a single new substance.
Because the processes involve opposite chemical changes—breaking down versus building up—a decomposition reaction is considered the opposite of a combination reaction.

(C) The reaction between calcium oxide $(CaO)$, also known as quicklime, and water $(H_2O)$ is a highly exothermic combination reaction.
The chemical equation for this reaction is: $CaO(s) + H_2O(l) \rightarrow Ca(OH)_2(aq) + \text{Heat}$.
In this process, calcium oxide reacts with water to form calcium hydroxide $(Ca(OH)_2)$, also known as slaked lime.
Since this reaction releases a large amount of heat, it is classified as an exothermic reaction.

(N/A) Copper is more reactive than silver. In the reactivity series,it is placed above silver. So,copper displaces silver from its salt.
Observation:
$(i)$ The colour of the solution turns bluish green due to the formation of copper nitrate.
$(ii)$ $A$ greyish-white deposit of silver is observed on the surface of the copper wire.
$(b)$ The balanced chemical equation is:
$Cu(s) + 2AgNO_3(aq) \to Cu(NO_3)_2(aq) + 2Ag(s)$

(D) Black and white photography utilizes the light-sensitive nature of silver halides.
When silver bromide $(AgBr)$ is exposed to sunlight,it undergoes a photochemical decomposition reaction.
The reaction is: $2 AgBr(s) \xrightarrow{\text{Sunlight}} 2 Ag(s) + Br_{2}(g)$.
In this process,silver bromide decomposes into metallic silver $(Ag)$ and bromine gas $(Br_{2})$,which creates the image on the photographic film.

(A) double displacement reaction is a chemical reaction where two reactant ionic compounds exchange ions to form two new products.
Analysis of the given reactions:
$(i)$ $Pb + CuCl_2 \longrightarrow PbCl_2 + Cu$: This is a displacement reaction where $Pb$ displaces $Cu$.
$(ii)$ $Na_2SO_4 + BaCl_2 \longrightarrow BaSO_4 + 2NaCl$: This is a double displacement reaction where $Na^+$ and $Ba^{2+}$ ions exchange places.
$(iii)$ $C + O_2 \longrightarrow CO_2$: This is a combination reaction.
$(iv)$ $CH_4 + 2O_2 \longrightarrow CO_2 + 2H_2O$: This is a combustion reaction.
Therefore,only reaction $(ii)$ is a double displacement reaction.

(A) Silver chloride $(AgCl)$ is a light-sensitive compound.
When exposed to sunlight,it undergoes a photochemical decomposition reaction.
The chemical equation for this reaction is: $2AgCl(s) \xrightarrow{sunlight} 2Ag(s) + Cl_2(g)$.
In this process,silver chloride decomposes to form metallic silver $(Ag)$,which is grey in color,and chlorine gas $(Cl_2)$ is released.
Therefore,statement $(i)$ is correct because silver is formed,and statement $(iii)$ is correct because chlorine gas is released due to the decomposition of silver chloride.
Thus,both $(i)$ and $(iii)$ are true.

(D) The reaction between potassium iodide $(KI)$ and lead nitrate $(Pb(NO_3)_2)$ is a double displacement reaction that produces a yellow precipitate of lead iodide $(PbI_2)$.
$2KI(aq) + Pb(NO_3)_2(aq) \rightarrow PbI_2(s) + 2KNO_3(aq)$
To obtain the yellow precipitate of lead iodide,we need a soluble lead salt that can provide lead ions $(Pb^{2+})$ in the aqueous solution.
Lead sulphate is insoluble in water,so it cannot be used.
Potassium sulphate and ammonium nitrate do not contain lead ions.
Lead acetate $(Pb(CH_3COO)_2)$ is a soluble lead salt that dissociates to provide $Pb^{2+}$ ions,which react with iodide ions to form the yellow precipitate of lead iodide. Therefore,lead acetate is the correct substitute.

(B) combination reaction is a reaction in which two or more reactants combine to form a single product.
$(i)$ $2 KClO_{3} \longrightarrow 2 KCl + 3O_{2}$ is a decomposition reaction because one reactant breaks down into multiple products.
$(ii)$ $MgO + H_{2}O \longrightarrow Mg(OH)_{2}$ is a combination reaction because two reactants combine to form a single product.
$(iii)$ $4 Al + 3O_{2} \longrightarrow 2 Al_{2}O_{3}$ is a combination reaction because two reactants combine to form a single product.
$(iv)$ $Zn + FeSO_{4} \longrightarrow ZnSO_{4} + Fe$ is a displacement reaction because $Zn$ displaces $Fe$ from its salt solution.
Therefore,$(ii)$ and $(iii)$ are combination reactions.

(A) $(TRUE)$ The statement is $True$. Ferrous sulphate crystals $(FeSO_4 \cdot 7H_2O)$ are light green in colour. Upon heating,they first lose water of crystallisation to become anhydrous ferrous sulphate $(FeSO_4)$,which is white or greyish-white. Further heating leads to the decomposition of ferrous sulphate into ferric oxide $(Fe_2O_3)$,sulphur dioxide $(SO_2)$,and sulphur trioxide $(SO_3)$.

(TRUE) The statement is $True$.
When lead nitrate $(Pb(NO_3)_2)$ is heated, it undergoes thermal decomposition to form lead oxide $(PbO)$, nitrogen dioxide $(NO_2)$, and oxygen $(O_2)$.
The chemical equation is: $2Pb(NO_3)_2(s) \xrightarrow{\Delta} 2PbO(s) + 4NO_2(g) + O_2(g)$.
The brown fumes observed are due to the evolution of nitrogen dioxide $(NO_2)$ gas.

(FALSE) The statement is False.
Silver bromide $(AgBr)$ undergoes a photochemical decomposition reaction when exposed to light,breaking down into silver $(Ag)$ and bromine $(Br_2)$.
This reaction is primarily used in black and white photography,not in the manufacturing of cement.

(TRUE) The statement is true.
In a chemical reaction,when two solutions are mixed,if an insoluble solid is formed,it is called a precipitate. This type of reaction is known as a precipitation reaction.

(FALSE) False. In an endothermic reaction,heat is absorbed from the surroundings by the reacting substances. Conversely,in an exothermic reaction,heat is released from the reacting substances to the surroundings.

(FALSE) False.
This reaction is an example of a displacement reaction (specifically,a single displacement reaction).
In this reaction,a more reactive metal,$Zn$,displaces a less reactive metal,$Cu$,from its salt solution $(CuSO_4)$.
$A$ double displacement reaction involves the exchange of ions between two reactants,which is not the case here.

(A) The reaction between hydrogen $(H_{2})$ and chlorine $(Cl_{2})$ is a photochemical reaction.
In the presence of sunlight,these two gases react to form hydrogen chloride $(HCl)$ gas.
The chemical equation for this reaction is: $H_{2}(g) + Cl_{2}(g) \xrightarrow{\text{sunlight}} 2HCl(g)$.
This reaction does not occur in the dark and requires the energy provided by sunlight to break the bonds in the reactant molecules.

(B) When ammonia gas $(NH_3)$ reacts with hydrogen chloride gas $(HCl)$,they undergo a chemical reaction to form solid ammonium chloride $(NH_4Cl)$.
The balanced chemical equation for this reaction is:
$NH_3(g) + HCl(g) \rightarrow NH_4Cl(s)$
This reaction is characterized by the formation of dense white fumes of ammonium chloride.

(C) When sulfur dioxide $(SO_2)$ gas is passed through lime water (calcium hydroxide,$Ca(OH)_2$),it reacts to form calcium sulfite $(CaSO_3)$ and water.
The chemical equation is: $Ca(OH)_2(aq) + SO_2(g) \rightarrow CaSO_3(s) + H_2O(l)$.
Calcium sulfite $(CaSO_3)$ is an insoluble white precipitate,which makes the lime water appear milky.