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Equilibrium in physical processes - class-XI

Description: Chemical equilibrium and acids-bases
Number of Questions: 18
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Tags: chemical equilibrium and acids-bases chemical equilibrium chemistry equilibrium
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An equilibrium expression may be forced to completion by:

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. adding a catalyst

  2. increasing the pressure

  3. increasing the temperature

  4. removing the products from the reaction mixture as they are formed

  5. decreasing the reactant concentration

Show answer
Correct Option: D
Explanation:

According to Le-chatelier principal reaction moves in forward direction if we remove products with time.so removing the products from the reaction mixture as they are formed may be forced to completion of an equilibrium expression.

${N} _{2}(g)+3{H} _{2}(g)\rightleftharpoons 2{NH} _{3}(g)+heat$
For the reaction above, what is the effect on the equilibrium position when the pressure is decreased?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. Increased production of products

  2. Increased production of reactants

  3. Fluctuations in the amounts of reactants and products

  4. No impact on the equilibrium

  5. Cannot be determined

Show answer
Correct Option: B
Explanation:

The given reaction is :-

${ N } _{ 2 }\left( g \right) +3{ H } _{ 2 }\left( g \right) \rightleftharpoons 2{ NH } _{ 3 }\left( g \right) +heat$
In this equilibrium, the forward reaction is accompanied by decrease in total no. of moles of gaseous species. If pressure on the system is decreased, the equilibrium shifts to the direction in which no. of moles increases as per Le Chatelier's principle. So, the backward reaction is favoured and reactants production is increased.

In a closed container rates of evaporation and condensation are same. What this statement indicate?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. A general rule for predicting solubility

  2. Conversion of solid phase to the liquid phase

  3. It represents relationship between absolute temperature and the kinetic energy of particles

  4. It represents relationship between volume and temperature at constant pressure

  5. A state in which the liquid and gas phases are in equilibrium

Show answer
Correct Option: E
Explanation:

Evaporation is the process of conversion from a liquid state to gaseous state.

Condensation is the process of conversion from the gaseous state to a liquid state. If a rate of the evaporation rate of condensation 
$\Rightarrow \quad $ Liquid & gas phases are in equilibrium.
This is the condition for physical equilibrium.

Which of the following solutions show positive deviation from Raoult's law?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. Acetone + Ethanol

  2. Acetone + Benzene

  3. Water + Methanol

  4. All of the above

Show answer
Correct Option: D

Ideal solutions doesn't obey Roult's law.

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Ideal solutions obey Raoult's law. Raoult's law states that the partial vapour pressure of each component an Ideal solution is equal to the vapour pressure of the pure component at that temperature multiplied by its mole fraction.

An increase in pressure will change the equilibrium by:

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. shifting to the side where a smaller volume results

  2. shifting to the side where a larger volume results

  3. favoring the endothermic reaction

  4. favoring the exothermic reaction

  5. none of the above

Show answer
Correct Option: A
Explanation:

An increase in pressure will change the equilibrium by shifting to the side from higher number of moles to lower number of moles. 

Which of the following is false of a binary solution showing false deviation from Roult's law?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. $P _A < X _AP _A^o$

  2. $\Delta H _{mix} < 0$

  3. $\Delta V _{mix} < 0$

  4. None of the above

Show answer
Correct Option: D

Volume of mixing for a liquid solution is :

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. may be positive or negative depending on the nature of liquids

  2. 0

  3. +ve

  4. -ve

Show answer
Correct Option: A

What is not something that a phase equilibrium line shows?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. The equilibrium point between solid and liquid

  2. The equilibrium point between liquid and gas

  3. The equilibrium point between liquid and solid

  4. The equilibrium point between solid and gas

  5. The equilibrium point between gas and vapor

Show answer
Correct Option: E
Explanation:

The phase equilibrium line does not show the equilibrium point between gas and vapor.
Because the gas and vapor belongs to the same phase.


The correct option is $E$.

Which of the following solutions does not  show positive deviation? 

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. Acetone and Ethanol

  2. Toluene and Benzene

  3. Water and Ethanol

  4. Water and Methanol

Show answer
Correct Option: B

At 373 K, steam and water are in equilibrium and $\Delta H$ = 40.98 kJ $mol^{-1}$.What will be  $\Delta S$ fro conversion of water into steam?
$H _2O _{(l)} \rightarrow H _2O _{(g)}$

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. 109.8 J $K^{-1}mol^{-1}$

  2. 31 J $K^{-1}mol^{-1}$

  3. 21.98 J $K^{-1}mol^{-1}$

  4. 326 J $K^{-1}mol^{-1}$

Show answer
Correct Option: A
Explanation:

The given reaction is :-

${ H } _{ 2 }O\left( l \right) \longrightarrow { H } _{ 2 }O\left( g \right) $
So, we have
       $\triangle Svap=\dfrac { \triangle Hvap }{ Tb } $
                     $=\dfrac { 40.98\times 1000 }{ 373 } =109.8{ JK }^{ -1 }{ mol }^{ -1 }$

At what temperature liquid water will be in equilibrium with water vapour?
$\Delta H _{vap} = 40.73 \ kJ \ mol^{-1}$, $\Delta S _{vap} = 0.109 \ kJ \ K^{-1} \ mol^{-1}$, 

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. 282.4 K

  2. 373.6 K

  3. 100 K

  4. 400 K

Show answer
Correct Option: B
Explanation:

The given reaction is :-

               ${ H } _{ 2 }O\left( l \right) \rightleftharpoons { H } _{ 2 }O\left( g \right) $
Now, at equilibrium, $\triangle G=0$
Now, from fibb's free energy change equation
         $\triangle G=\triangle H-T\triangle S$
$\Rightarrow \quad \triangle H=T\triangle S$
$\Rightarrow \quad T=\dfrac { \triangle H }{ \triangle S } =\dfrac { 40.73 }{ 0.1079 } =373.6K$
$\left( \because \triangle Hrap=40.73KJ/mol,\quad \triangle Srap=0.109KJ{ K }^{ -1 }{ mol }^{ -1 } \right) $

In physical equilibrium, forces responsible for equilibrium are _______ in  nature.

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. physical

  2. chemical

  3. strong

  4. weak

Show answer
Correct Option: A
Explanation:

In physical equilibrium, forces responsible for equilibrium are physical in nature (factual).

Which of the following represent physical equlibrium?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. Dissolution of solid $KI$ in water

  2. Sublimation of $NH _4Cl$

  3. Evaporation of dry ice in a closed container

  4. Condesation of water vapours

Show answer
Correct Option: A

A yellow precipitate obatined in II group of the equilibrium analysis was soluble in aq. $NaOH$ and insoluble in dil. $HNO _3$. This shows the presence of:

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. $Tin$

  2. $Antimony$

  3. $Arsenic$

  4. $Cadmium$

Show answer
Correct Option: A

Which of the following statements is incorrect ?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. In equilibrium mixture of ice water kept in perfectly insulated flask mass of ice and water does not change with time .

  2. The intensity of red colour increase when oxalic acid is added to a solution containing iron (III) nitrate and potassium thioyanate .

  3. On addition of catalyst equilibrium constant value is not affected .

  4. Equilibrium constant for a reaction with negative $\triangle H$ value decreases as the temperature increases .

Show answer
Correct Option: A

Two flasks A and B of an equal volume containing 1 mole and 2 moles of O$ 3$ respectively are heated to the same temperature. When the reaction $2O _3 \rightleftharpoons 3O _2$ practically stops, then both the flasks shall have __________.

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. the same ratio: $[O _2]/[O _3]$

  2. the same ratio: $[O _2]^{3/2}/[O _3]$

  3. only $O _2$

  4. the same time to reach equilibrium

Show answer
Correct Option: B
Explanation:

For the given reaction,
$K _c = \displaystyle \frac{[O _2]^3}{[O _3]^2}= constant$     so  $\displaystyle \sqrt{K _c} = \frac{[O _2]^{3/2}}{[O _3]} = constant$
Same for both containers. Kc won't change as flasks are heated to same temperature. 

Which of the following is not a general characteristic of equilibrium involving physical processes ?

chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. equilibrium is possible only in a closed system at a given temperature .

  2. all measurable properties of the system remain constant .

  3. all the physical processes stop at equilibrium.

  4. the opposing processes occur at the same ratio and there is dynamic but stable condition .

Show answer
Correct Option: C
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