Tag: chemistry

Questions Related to chemistry

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

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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. $Cadmium$

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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 .

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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 .

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Correct Option: C

Nitro benzene is used _________.

chemistry organic nitrogen compounds nitroarenes- preparation and properties nitro compounds types of organic reactions

  1. as a solvent

  2. In the manufacture of aniline

  3. In cheap scent

  4. All these

Show answer
Correct Option: D
Explanation:

It is a solvent because it can dissolve a large number of polar substances (polar aprotic solvent)
It can be used to manufacture aniline because it can be reduced by stephen's reduction to anniline
It is also used as a scent because it has pleasant odour

Nitrobenzene is used as a/an ____________.

chemistry organic nitrogen compounds nitroarenes- preparation and properties nitro compounds types of organic reactions

  1. reducing agent

  2. oxidizing agent

  3. nitrating agent

  4. neutralizing agent

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Correct Option: B
Explanation:

Nitrobenzene can itself be reduced to aniline, so it acts as an oxidising agent.