Tag: surface chemistry

Quizzes (6) Questions (144)

Questions Related to surface chemistry

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

In chemical reaction, the catalyst: 

  1. alters the amount of product

  2. lowers the activation energy
  3. decreases $A$ of forward reaction
  4. increases $A$ of forward reaction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A catalyst is the substance which speed up the chemical reaction by lowering the activation energy of reaction but it do not effects the amount of forward and backward reaction.
Hence option B is correct.

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

An example of an autocatalytic reaction is: 

  1. hydrogenation of oils

  2. decomposition of nitroglycerine
  3. oxidation of $Na _3AsO _3$ in presence of $Na _2SO _3$
  4. thermal decomposition of $KClO _3$ in presence of $MnO _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reaction mechanism for the decomposition of nitroglycerine $4C _3H _5N _3O _9 \rightarrow 6N _2 + 12CO _2 + 10H _20 + O _2$.
This reaction is auto catalytic which is based upon internal redox chemistry.

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

Which acts as poison for Pd-charcoal in Lindlar's catalyst?

  1. $BaSO _4$

  2. Quinoline
  3. Both $A$ and $B$

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A Lindlar catalyst is a heterogeneous catalyst which  consists of palladium deposited on calcium carbonate which is then poisoned with various forms of lead or sulphur not with $BaSO _4$ and quiniline. It is used for the hydrogenation of alkynes to alkenes.

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

The efficiency of an enzyme in catalysing a reaction is due to its capacity: 

  1. to form a strong enzyme substrate complex

  2. to decrease the bond energies in the substrate molecule

  3. to change the shape of the substrate molecule

  4. to lower the activation energy of the reaction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells by lowering the activation energy required for the reaction. It alters the pathway but doesn't take part in the reaction.

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

Which is not the characteristic of a catalyst?

  1. It changes the equilibrium point.

  2. It initiates the reaction.

  3. It alters the rate of reaction.

  4. It increases the average K.E. of molecules.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A catalyst is a substance which speed up the chemical reaction by lowering the activation energy of reaction but it does not change the equilibrium point.

Hence, the correct option is $\text{A}$

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

Regarding criteria of catalysis which one of the following statements is not true?

  1. The catalyst is changed chemically during the reaction.

  2. A small quantity of catalyst is often sufficient to bring about a considerable amount of the reaction.

  3. In reversible reaction, the catalyst alters the equilibrium position.

  4. The catalyst accelerates the rate of reaction.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The effect of catalyst is to increase speed of reaction by lowering the activation energy
As it affect forward and backward reaction equally hence it don't change any thermodynamical aspects of reaction.
Further catalyst don't take part in reaction so it don't change the final products.

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

In the titration between oxalic acid and acidified potassium permanganate, the manganous salt formed during the reaction and catalyses the reaction. The manganous salt acts as: 

  1. promoter

  2. positive catalyst

  3. autocatalyst

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the tit-ration between oxalic acid and acidified potassium permanganate, the manganous salt formed during the reaction and catalyses the reaction. The manganous salt acts as auto catalyst because the rate of reaction depends on the manganous ions formed,so manganous ions catlyze the reaction.
Hence option C is correct.

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

In case of autocatalysis: 

  1. reactant catalyses

  2. heat produced in the reaction catalyses

  3. product catalyses

  4. solvent catalyses
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Autocatalysis is the reaction where one of the products formed catalyzes the reaction. So in case of auto catalysis product catalyses the reaction. Hence catalysis of a reaction by one of its products is called autocatalysis.