Tag: catalysis

Questions Related to catalysis

What does a catalyst do?

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. Alter the state of equilibrium.

  2. Decreases the activation energy.

  3. Increases collision frequency.

  4. Increases the average kinetic energy of reacting species.

Show answer
Correct Option: B
Explanation:

Catalyst is a substance, which lowers the activation energy of reaction because it provides an alternate pathway for reaction. Also, it increases backward and forward reaction to the same extent. Due to this lower activation energy, equilibrium is attained faster.

Which of the following are electrophiles?

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. $BF _3$

  2. $: CCl _2$

  3. $^{\oplus}NH _4$

  4. $I^{\ominus}$

Show answer
Correct Option: C

Which of the following is the best way to speed up a chemical reaction?

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. Make an effort to concentrate the reactants as best as possible

  2. Add a catalyst

  3. Cool the reaction down

  4. Increase the pressure on the system

Show answer
Correct Option: B
Explanation:
5 ways to increase the reaction rate :
1. The nature of the reactants: A reaction between two gases would be faster than a reaction between to liquids or two solids.
2. Temperature:  The heat causes the particles to move quickly, and due to the Collision Theory,  the reaction will occur faster.
3. Concentration: The higher the concentration of a reactant, the quicker the reaction will occur. 
4. Surface Area: The more the particles are exposed, the faster it is for the other reactant to collide into the particles, meaning the reaction rate will increase.
5. Catalysts: Catalysts are substances that increase the rate of reaction by speeding up the reaction without being used up in the reaction.
Adding catalyst can most effectively speed up the chemical reaction. 

Competitive inhibition is reversible.

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Competitive Inhibitors belong to the category of enzymes known as reversible inhibitors. Reversible inhibitors dissociate the enzyme-inhibitor complex as soon as possible.

This Chemical reaction can be reversed by increasing concentration of substrate. These process continuously takes place as $E + S \rightarrow ES \rightarrow E + P$

The structural resemblence of substrate and inhibitor leads to______________ inhibition.

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. non-competitive

  2. competitive

  3. both $A$ and $B$

  4. none of the above

Show answer
Correct Option: B
Explanation:

Competitive Inhibitor - A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate.

Non-competitive Inhibitor - A non-competitive inhibitor is a substance that interacts with the enzyme, but usually not at the active site. The noncompetitive inhibitor reacts either remote from or very close to the active site.

The process which is catalysed by one of the product is called :

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. acid - base catalysis

  2. autocatalysis

  3. negative catalysis

  4. homogeneous catalysis

Show answer
Correct Option: B
Explanation:

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Catalysts are generally foreign substances but sometimes one of the product formed may act as a catalyst and such a catalyst is called "auto catalyst" and the phenomenon is called auto catalysis.0
A chemical reaction is said to have undergone autocatalysis, if the reaction product itself is the catalyst for that reaction.

A catalyst increases the rate of a reaction by:

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. increasing the activation energy of the reaction

  2. increasing the value of rate constants $(k _f$ and $k _b)$

  3. increasing the enthalpy change of the reaction

  4. decreasing the enthalpy change of the reaction

Show answer
Correct Option: C
Explanation:

A catalyst increases rate of reacting by decreasing activation energy. and increasing the enthalpy change of the reaction

The auto catalyst in the decomposition of arsine to Arsenic and $H _2$ is

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. $As _2O _3$

  2. $As$

  3. $H _2$

  4. $Ge$

Show answer
Correct Option: A

Which of the following is used as autocatalyst

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. $ KMnO _4 $

  2. $ AI _2O _3 $

  3. $ CaC _3 $

  4. All of these

Show answer
Correct Option: A

Which one of the following reactions is an example of auto-catalysis ?

enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

  1. $2{ AsH } _{ 3 }(s)\rightarrow 2As(s)+3{ H } _{ 2 }(g)$

  2. ${ N } _{ 2 }(g)\rightarrow 3{ H } _{ 2 }(g)\overset { Fe(g) }{ \rightarrow } 2N{ H } _{ 3 }(g)$

  3. ${ 2SO } _{ 2 }(g)\rightarrow { O } _{ 2 }(g)\overset { NO(g) }{ \rightarrow } 2S{ O } _{ 3 }(g)$

  4. ${ C } _{ 12 }{ H } _{ 22 }{ O } _{ H }(l)+{ H } _{ 2 }O(l)\overset { { H }^{ - }(l) }{ \rightarrow } { C } _{ 6 }{ H } _{ 12 }{ O } _{ 6 }(l){ HC } _{ 6 }{ H } _{ 12 }{ O } _{ 6 }(l)$

Show answer
Correct Option: A
Explanation:

Auto-catalysis is defined as the reaction that is catalyzed by one of its product.  in auto-catalysis product of reaction acts as a catalyst for the reaction.  In auto-catalysis the initial rate of reaction rises as the catalytic product is formed instead of decreasing steadily.  

for example: the free arsenic produced by decomposition of arsine auto catalyses the reaction. The thermal decomposition of Arsine produces arsenic and hydrogen.  2AsH3 forms 2As + 3H2