Catalyst and Catalysis Questions in English

(D) catalyst $X$ provides an alternative pathway for the reaction with lower activation energy.
It increases the rate of both the forward and backward reactions to the same extent.
Therefore,it does not change the position of equilibrium or the value of the equilibrium constant ($K_c$ or $K_p$).
Thus,the correct statement is that it does not affect the equilibrium constant of the reaction.

(B) In the Haber process for the manufacture of $NH_3$,$Fe$ is used as a catalyst and $Mo$ is used as a promoter to increase the efficiency of the catalyst.

(B) catalyst provides an alternative reaction pathway with a lower activation energy $(E_a)$.
By lowering the energy barrier,a larger fraction of reactant molecules possess energy greater than the threshold energy,thereby increasing the rate of the reaction.

(B) catalyst provides an alternative reaction pathway with a lower activation energy $(E_a)$.
By lowering the activation energy,a larger fraction of reactant molecules possess sufficient energy to cross the energy barrier at a given temperature,thereby increasing the rate of the reaction.

(A) catalyst provides an alternative reaction pathway with a lower activation energy $(E_a)$.
It does not affect the equilibrium constant $(K_{eq})$,reaction entropy $(\Delta S)$,or reaction enthalpy $(\Delta H)$.
Therefore,only the activation energy changes.

(A) According to the adsorption theory of catalysis,the catalyst provides a surface where reactant molecules get adsorbed.
This adsorption increases the concentration of reactants at the active sites and,more importantly,it provides an alternative pathway with lower activation energy,thereby increasing the rate of the reaction.

(C) The adsorption theory of catalysis is applicable to $Heterogeneous \ catalysis$.
In this process,the reactant molecules are adsorbed on the surface of the solid catalyst,which increases the concentration of reactants at the surface and facilitates the reaction.

(B) catalyst is a substance that alters the rate of a chemical reaction without itself undergoing any permanent chemical change.
It can either increase the rate (positive catalyst) or decrease the rate (negative catalyst) of a reaction.
Therefore,it is used for altering the velocity of the reaction.

(D) The correct answer is $(D)$.
$A$ catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
It provides an alternative reaction pathway with a lower activation energy,but it does not participate in the overall stoichiometry of the reaction and is recovered unchanged at the end.

(A) In Haber's process,the synthesis of ammonia is represented by the reaction: $N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)}$.
Finely divided iron $(Fe)$ is used as a catalyst to increase the rate of reaction.
Molybdenum $(Mo)$ is used as a promoter to increase the efficiency of the iron catalyst.
Therefore,the correct statement is that finely divided iron is used as a catalyst.

(D) The decomposition of potassium chlorate $(KClO_3)$ is a slow process.
When manganese dioxide $(MnO_2)$ is added,it acts as a positive catalyst.
$A$ catalyst provides an alternative reaction pathway with a lower activation energy,thereby increasing the rate of the reaction.
The balanced chemical equation is: $2KClO_3 \xrightarrow{MnO_2} 2KCl + 3O_2$.

(D) $Zeolites$ are shape-selective catalysts.
Their catalytic action depends upon the pore structure,the size of the apertures,and the size of the cavities within the $Zeolite$ framework.
Therefore,all of these factors influence the reaction.

(A) catalyst provides an alternative reaction pathway with a lower activation energy $(E_a)$.
By lowering the activation energy,a greater fraction of reactant molecules possess sufficient energy to cross the energy barrier at a given temperature.
This leads to an increase in the rate of the reaction.
Catalysts do not change the thermodynamic properties like Gibbs free energy change $(\Delta G)$ or enthalpy change $(\Delta H)$ of the reaction.

(B) Autocatalysis is a phenomenon where one of the products formed during a chemical reaction acts as a catalyst for the same reaction.
As the reaction proceeds,the concentration of the product increases,which in turn increases the rate of the reaction.
Therefore,in the case of auto catalysis,the product catalyses the reaction.

(B) The correct answer is $(B)$.
In the given reaction,sucrose $(C_{12}H_{22}O_{11})$ is in the aqueous phase,water $(H_2O)$ is in the liquid phase,and the catalyst dilute $H_2SO_4$ is also in the liquid/aqueous phase.
Since the reactant and the catalyst are in the same physical state (liquid/aqueous),the catalyst is known as a homogeneous catalyst.

(A) The enzyme $Zymase$ is responsible for the fermentation of glucose into ethanol and carbon dioxide.
The chemical reaction is as follows:
$C_6H_{12}O_6 \xrightarrow{\text{Zymase}} 2C_2H_5OH + 2CO_2$

(D) catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
$1$. It provides an alternative pathway with lower activation energy $(E_a)$.
$2$. Although it may participate in the reaction mechanism,it is regenerated at the end of the process.
$3$. It speeds up both the forward and backward reactions equally,thus it does not change the equilibrium constant $(K_{eq})$ or the position of equilibrium.
Therefore,all the given statements are correct.

(D) catalyst provides an alternative reaction pathway with a lower activation energy. It does not alter the thermodynamic properties of the reaction,such as the enthalpy of the reactants or products,nor does it change the equilibrium constant. Therefore,statement $D$ is correct.

(A) catalyst does not change the equilibrium constant because it affects both the forward and backward reaction rates to the same extent.
It provides an alternative reaction pathway with a lower activation energy,which increases the rate of reaction.
It does not increase the average kinetic energy $(K.E.)$ of the molecules.
Therefore,both $A$ and $D$ are not characteristics of a catalyst,but in the context of standard multiple-choice questions,$A$ is the most fundamental thermodynamic property that remains unchanged.

(C) catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy.
It does not alter the equilibrium constant or the overall Gibbs free energy change $(\Delta G)$ of the reaction.
Therefore,the correct option is $(C)$.

(D) catalyst provides an alternative reaction pathway with lower activation energy. Therefore,$(d)$ Activation energy changes when a catalyst is used in a reaction.

(C) The reaction between oxalic acid $(H_2C_2O_4)$ and acidified potassium permanganate $(KMnO_4)$ is slow at room temperature.
As the reaction proceeds,$Mn^{2+}$ ions are produced.
These $Mn^{2+}$ ions act as a catalyst for the reaction,increasing its rate.
Since the product of the reaction itself acts as a catalyst,this phenomenon is known as autocatalysis,and the substance is called an autocatalyst.

(D) catalyst is a substance that increases the rate of a reaction by providing an alternative pathway with a lower activation energy $(E_a)$.
In heterogeneous catalysis,the reactants and the catalyst are in different phases,and the reaction occurs on the surface of the catalyst.
Statement $A$ is correct because catalysts lower the activation energy.
Statement $B$ is correct as the catalyst often forms intermediate surface compounds with the reactants.
Statement $C$ is correct because the adsorption of reactants on the catalyst surface is a key step.
Statement $D$ is incorrect because the primary function of any catalyst is to change (specifically lower) the activation energy of the reaction.

(C) The effect of a catalyst is to increase the speed of a reaction by lowering the activation energy.
Since it affects the forward and backward reactions equally,it does not change the equilibrium position or any thermodynamic aspects of the reaction.
Furthermore,a catalyst does not take part in the reaction stoichiometry,so it remains unchanged chemically at the end of the reaction.

(A) catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy.
It does not initiate a reaction that would not otherwise occur.
It does not alter the equilibrium constant of the reaction,as it speeds up both the forward and backward reactions equally.

(A) The reaction $2SO_{2(g)} + O_{2(g)} \longrightarrow 2SO_{3(g)}$ occurs in the presence of platinized asbestos as a catalyst.
Since the catalyst (platinized asbestos,a solid) exists in a different phase from the reactants (gases),this is an example of a heterogeneous catalyst.

(D) The hydrogenation of vegetable oils to produce solid fats (like ghee) is a catalytic process.
$Ni$ (Nickel) is commonly used as a heterogeneous catalyst for this reaction.
The reaction is represented as: $\text{Oil} + H_2 \xrightarrow{Ni} \text{Ghee}$.

(A) In the $Ostwald$ process,ammonia is oxidized to nitric acid using a platinum gauge as a catalyst.
$4NH_{3} + 5O_{2} \xrightarrow[1100 \ K]{Pt \ gauge} 4NO + 6H_{2}O$
$2NO + O_{2} \rightarrow 2NO_{2}$
$4NO_{2} + 2H_{2}O + O_{2} \rightarrow 4HNO_{3}$

(B) The hydrolysis of an ester in the presence of an acid (protons,$H^+$) is a classic example of acid-catalyzed reaction. \\ In this process,the proton acts as a catalyst by protonating the carbonyl oxygen of the ester,which makes the carbonyl carbon more electrophilic and susceptible to nucleophilic attack by water. \\ Since the catalyst (protons) and the reactants (ester and water) are in the same phase (liquid),it is classified as homogeneous catalysis,specifically acid-base catalysis.

(B) catalyst is a substance that lowers the activation energy of a reaction by providing an alternate pathway. Generally,a catalyst increases the rate of a reaction.
In the Haber's process,$Fe$ is used as a catalyst.
In the Ostwald process,$Pt/Rh$ is used as a catalyst.
In the Contact process,$V_2O_5$ is used as a catalyst.
The Thermite process involves the reduction of metal oxides by aluminum,such as $2 Al + Fe_2O_3 \rightarrow Al_2O_3 + 2 Fe$. This is a highly exothermic,self-sustaining redox reaction that does not require a catalyst.

(C) In the hydrogenation of oils,finely divided nickel $(Ni)$ is used as a catalyst,not iron $(Fe)$.
Therefore,the statement in option $C$ is incorrect.

(D) catalyst is a substance that alters the rate of a chemical reaction without itself undergoing any permanent chemical change at the end of the reaction.

(B) catalyst is a substance that increases the rate of a reaction without itself being consumed at the end of the reaction.
It is important to note that a catalyst cannot initiate a reaction that is not thermodynamically feasible.
It only lowers the activation energy,thereby increasing the rate of reaction.
Therefore,the statement that a catalyst can initiate a reaction is false.

(B) Homogeneous catalysis occurs when the reactants and the catalyst are in the same phase.
In the reaction $2SO_{2(g)} + O_{2(g)} \xrightarrow{NO_{(g)}} 2SO_{3(g)}$,both the reactants ($SO_2$ and $O_2$) and the catalyst $(NO)$ are in the gaseous phase.
Therefore,this reaction represents homogeneous catalysis.
In all other options,the catalyst is in the solid phase while the reactants are in the gaseous phase,representing heterogeneous catalysis.

(D) In the contact process for the manufacture of $H_2SO_4$,platinised asbestos acts as a catalyst for the oxidation of $SO_2$ to $SO_3$.
$As_2O_3$ (arsenic oxide) present as an impurity acts as a catalytic poison,which binds to the active sites of the catalyst and reduces its efficiency.
$2SO_2 + O_2 \xrightarrow[As_2O_3 \text{ (poison)}]{\text{Platinised asbestos (catalyst)}} 2SO_3$

(D) The function of a positive catalyst is to decrease the energy of activation and hence increase the rate of reaction in the forward direction. Therefore,the statement that positive catalysts raise the energy of activation is incorrect. Thus,option $(D)$ is wrong.

(D) Option $(D)$ is incorrect. In the industrial manufacture of ammonia,known as the $Haber$ process,finely divided $Fe$ is used as a catalyst,not $Ni$.

(B) Homogeneous catalysis is defined as a process where the catalyst and the reactants exist in the same phase (i.e.,they form a single phase).
For example,the oxidation of $SO_2$ to $SO_3$ in the presence of $NO$ gas as a catalyst is a homogeneous reaction because all components are in the gaseous phase.

(C) The oxidation of sulfur dioxide $(SO_2)$ to sulfur trioxide $(SO_3)$ is a key step in the Contact Process for the manufacture of sulfuric acid.
This reaction is catalyzed by vanadium$(V)$ oxide $(V_2O_5)$.
The chemical equation is: $2SO_2(g) + O_2(g) \xrightarrow{V_2O_5} 2SO_3(g)$.

(B) The reaction $2SO_{2(g)} + O_{2(g)} \to 2SO_{3(g)}$ is a key step in the Contact Process for the manufacture of sulfuric acid.
This reaction is slow and requires a catalyst,typically $Pt$ or $V_2O_5$,to proceed at a significant rate.
Therefore,the correct option is $(B)$.

(B) Catalysts are generally foreign substances,but sometimes one of the products formed in a reaction may act as a catalyst. Such a catalyst is called an $autocatalyst$ and the phenomenon is known as $autocatalysis$.

(A) Adam's catalyst is a common name for platinum dioxide,$PtO_2$,which is used as a catalyst in hydrogenation reactions.
Upon reduction in the reaction medium,it forms finely divided platinum metal,which acts as the active catalytic species.
Therefore,the correct option is $(A)$.

(D) catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. At the end of the reaction,the catalyst remains unchanged in terms of its $Mass$ and $Chemical \ composition$.

(C) Wilhelm Ostwald defined a catalyst as a substance that changes the rate of a chemical reaction without itself undergoing any permanent chemical change.

(B) catalyst is a substance that alters the rate of a chemical reaction without itself undergoing any permanent chemical change and without affecting the overall energetics of the reaction.

(D) Catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy,without being consumed in the process or affecting the overall equilibrium position.

(A) The correct answer is $A$. The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis.
$N_{2(g)} + 3H_{2(g)} \xrightarrow{Fe(s)} 2NH_{3(g)}$
In this reaction,the reactants ($N_2$ and $H_2$) are in the gaseous state,while the catalyst $(Fe)$ is in the solid state. Since they exist in different phases,it is an example of heterogeneous catalysis.

(B) The decomposition of $H_2O_2$ is a reaction that can be slowed down by adding substances like phosphoric acid $(H_3PO_4)$.
These substances are known as inhibitors or negative catalysts,as they decrease the rate of a chemical reaction.

(D) catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. It provides an alternative reaction pathway with a lower activation energy. Therefore,option $D$ is the most accurate description as it participates in the reaction mechanism (forming intermediates) but is regenerated at the end.

(C) catalyst is a substance that increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy,thereby shortening the time required to reach equilibrium without affecting the equilibrium constant or the final concentration of the products.