11th Class Chemistry Chapter eleven Short Questions with Answers Solved

Question: 1

Give two characteristics of enzyme catalyst?

Answer: 1

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There are following characteristics of an enzyme.

Enzymes catalysis is highly specific.
Rate of enzymatic reaction is maximum at optimum temperature and pH.
Enzymatic activities are enhanced by the presence of an activator.

Question: 2

Define catalytic poisoning with example?

Answer: 2

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Deactivation of catalyst by small amount of impurities is called catalytic poisoning.It may be temporary or permanent.

E.g. In Haber's process of CO as an impurity with hydrogen decreases the catalytic activity of catalyst

Question: 3

Compare order of reaction and molecularity?

Answer: 3

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Orde:

The number of molecules whose concentration change in a chemical reaction.
It is an experimental quantity.
It may be fractional.
It may be zero.

Question: 4

Define and give an example of the process of activation of catalyst?

Answer: 4

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A substance which promotes the activity of catalyst is called promoter or activator or catalyst for a catalyst.

E.g.Nickle is used as catalyst fro hydrogenation of vegetable oil and copper is used as activator.

Question: 5

Define catalysis.Name its two types?

Answer: 5

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The process which take place in the presence of a catalyst is called catalysis.

There are two types of it.

Homogeneous catalysis
Heterogeneous catalysis

Question: 6

Name two Physical methods used to determine the rate of a reaction?

Answer: 6

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Spectrometry
Electrical conductivity method
Dilatometric method
Refractometric method

Question: 7

How are enthalpy changes of reaction and energy of activation of reaction distinguished?

Answer: 7

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Energy of Activation:"The minimum amount of additional kinetic energy required by the reactants in addition to average kinetic energy for effective collisions and product formation Energy of activation.

Question: 8

A final divided catalyst may prove more effective why?

Answer: 8

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When a catalyst is finely divided, it has greater surface areas and possibilities of atoms and molecules of reactants to come in contact with each other increase and rate exchange.

E.g. CaCO₃ Reacts much more rapidly in powder form, as compared to its big pieces.

Question: 9

Discuss auto catalyst with example?

Answer: 9

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Question: 10

How does the catalyst affect the rate of a reaction?

Answer: 10

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A catalyst provides anew reaction path with low activation energy barriers.A greater number of molecules are able to get over the new energy barrier and reaction rate increases.

Question: 11

Define Activation Energy and Activated Complex.

Answer: 11

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The minimum amount of energy required for an effective collision is called activation energy.

Activated complex is an unstable combination of all the atoms involved

In the reaction for which the energy is maximum.It is a short lived species and decomposes into the products immediately.It has a transient existence, that is why it is also called a transition state.

Question: 12

The radioactive decay is always first order reaction.Explain?

Answer: 12

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The rate of radioactive decay depends on the amount of radioactive substance.Since only of substance is involved in this process therefore it is always a first order reaction.

Question: 13

What is pseudo first order reaction?Give an example.

Answer: 13

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The rate of reaction remains effectively independence of the concentration of water because being a solvent it is present in very large excess.Such type of reactions has been named as pseudo-first order reaction.

E.g.Hydrolysis of tertiary butyl bromide.

Question: 14

Define energy of Activation.How it is affected by temperature?

Answer: 14

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The minimum amount of energy which molecules must have in addition to their average K.E to form an activated complex is called activation energy. It is denoted by "E".

Many chemical reactions do not take place at room temperature because molecules have low K.E than the activation energy.Thus the activation energy is necessary to start a reaction.

Question: 15

How rate of reaction is determined by electrical conductivity method?

Answer: 15

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The rate of reaction involving ions can be studied by electrical conductivity method. The conductivity of such a solution depends upon the rate of change of concentration of the reacting ions or the ions formed during the reaction.The conductivity will be proportional to the rate of change in the concentration of such ions.

Question: 16

State rate of chemical reaction and give its units?

Answer: 16

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The rate of reaction is defined as the change in concentration of reactant or a product divided by the time taken for the change.

The rate of reaction has the units of concentration divided by time,Usually the concentration is expressed in mole dm^-3 And the time in second, thus the units for the reaction rates are moles dm_-3s^-1.

Question: 17

Define instantaneous and average rate of reaction?

Answer: 17

17-19

Instantaneous Rate of Reaction: The rate at any one instant during a specific interval of time is called instantaneous rate of reaction.

Average Rate of Reaction: The rate of reaction between two specific intervals of time is called average rate of reaction.

Question: 18

How higher temperature increase the rate of reaction?

Answer: 18

18-19

When we increase the temperature the average energy of the molecules increases. The number of those molecules also increase which can form an activated complex after collision.So by increasing temperature, number of effective collision increased and rate of reaction also increases.

Question: 19

Define negative catalyst along with an example?

Answer: 19

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A substance which decreases the rate of reaction is called negative catalyst or inhibitor.

E.g.Tetraethyl is added to petrol because it control pre-ignition of petrol.

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11th Class Chapter eleven Chemistry Short Questions

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