Tag: introduction to equilibrium

Questions Related to introduction to equilibrium

$4g \,H _2$ and $127g \,I _2$  are mixed and heated lit closed vessels until equilibrium is reached. If the equilibrium concentration of $HI$ is $0.05 \,M$ total number of moles present at equilibrium is:

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

  1. $3.25$

  2. $1.75$

  3. $2.25$

  4. $2.5$

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Correct Option: D
Explanation:

Given $H _2=4g$ & $I _2=127 g$

$\Rightarrow H _2=2$ mole & $I _2=0.5$ mole
$[HI] _{eqm}=0.05M$   $\therefore$ Moles of $HI=0.05$ mole
            $H _2\quad +\quad I _2\quad \rightleftharpoons\quad  2HI$
              $2$              $0.5$                  $0$         Initial
  $2-\cfrac {0.05}{2}$     $0.5-\cfrac {0.05}{2}$       $0.05$       Eqm
$\therefore$ Total moles at eqm,
$=\left(2-\cfrac {0.05}{2}\right)+\left(0.5-\cfrac {0.05}{2}\right)+0.05$
$=2.5$

For the reaction ${ CO(g)+H } _{ 2 }O(g)\rightleftharpoons { CO } _{ 2 }(g)+{ H } _{ 2 }(g)$ at a given temperature the equilibrium amount of ${ CO } _{ 2 }(g)$ can be increased by:

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

  1. Adding a suitable catalyst

  2. Adding an inert gas

  3. Decreasing the volume of container

  4. Increasing the amount of $CO(g)$

Show answer
Correct Option: D
Explanation:

$CO _(g)^+\ H _2(g)\rightleftharpoons CO _{2(g)}+H _{2(g)}$

$\Delta x=0$   $\therefore$ Adding inert gas & decreasing volume will have no effect. by increasing amount of CO, we shift reaction forward and to more $CO _2$.

Match the items in column - I with those in column - II

Column I Column II
1. Electric Fuse  A  Chemical Effect
2. Relay B Electric Discharge
3. CFL C Magnetic effect 
4. Button Cell D Heating Effect

Which of the following shows the correct matching ?

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

  1. 1 - C, 2 - B, 3 - A, 4 - D

  2. 1 - B, 2 - A, 3 - C, 4 - D

  3. 1 - D, 2 - C, 3 - B, 4 - A

  4. 1 - D, 2 - B, 3 - C, 4 - A

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Correct Option: C
Explanation:

Electric fuse is used to protect electric appliances. When current larger than specified value flows through the circuit, the temperature of the fuse wire increases. This melts the fuse wire and breaks the circuit.


 In relay transmission electromagnetic waves are used. 

CFL works on electric discharge. In button cell electrolytes are the sources of ions.

In the button cell electrolytes are sources of ions.

Option C is correct.

Equilibrium can be achieved only in open vessel.
chemistry chemical equilibrium equilibrium in chemical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. True

  2. False

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Correct Option: B
Explanation:

Equilibrium can be achieved in open vessel as well as in close vessel.

The reactions $PCl 5 (g)  \rightleftharpoons  PCl _3(g) + Cl _2 (g) $ and $COCl _2 (g)  \rightleftharpoons  CO(g) + Cl _2(g)$ are simultaneously in equilibrium in an equilibrium box at constant volume. A few moles of CO(g) are later introduced into the vessel. After some time, the new equilibrium concentration of_______.

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

  1. PCl$ _5$ will remain unchanged

  2. Cl$ _2$ will be greater

  3. PCl$ _5$ will become less

  4. PCl$ _5$ will become greater

Show answer
Correct Option: C
Explanation:

If CO is added 2$^{nd}$ equilibrium will proceed in the backward direction and concentration of Cl$ _2$ will decrease. This Cl$ _2$ will be further formed by the decomposition of PCl$ _5$.

If two gases $AB _2$ and $B _2C$ are mixed the following equilibria are readily established
$AB _2(g) + B _2 C(g)  \rightarrow AB _3(g) + BC(g)$
$BC(g) + B _2 C(g)  \rightarrow B _3 C _2 (g)$
If the reaction is started only with $AB _2$ with $B _2C$, then which of the following is necessarily true at equilibrium:

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

  1. $[AB _3] _{eq} = [BC] _{eq}$

  2. $[AB _2] _{eq} = [B _2C] _{eq}$

  3. $[AB _3] _{eq} > [B _3C _2] _{eq}$

  4. $[AB _3] _{eq} > [BC] _{eq}$

Show answer
Correct Option: C,D
Explanation:

Let reactions is started with a mole of $AB _2$ and b mole of $B _2C$
$\Rightarrow      AB _2 (g) + B _2C(g)  \rightarrow AB _3(g) + BC(g)$
                    a                 b               0               0
                  a - x           b - x - y        x              x - y
$BC(g) + B _2C(g)   \rightarrow B _2C _2 (g)$
    x - y            b - x - y        y                 As  x > y
Clearly $[AB _3] _{eq} > [B _3 C _2] _{eq} $ and  $[AB _3] _{eq}  >  [BC] _{eq}$

When the equilibrium is attained, the concentration of each of the reactants and products becomes equal.
chemistry chemical equilibrium equilibrium in chemical processes introduction to equilibrium chemical equilibrium and acids-bases

  1. True

  2. False

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Correct Option: B
Explanation:

When the equilibrium is attained, the concentration of each of the reactants and products may or may not become equal.  It may happen that the concentrations of products are higher than the concentrations of the reactants. Or, it may happen that the concentrations of the reactants are higher than the concentrations of the products.

At 373 K,a gaseous reaction $A\rightarrow 2B+C$ is found to be of first order.Starting with pure A,the total pressure at the end of 10 min was 176 mm of Hg and after a long time when A was completely dissociated,it was 270 mm of Hg.The pressure of A at the end of  10 minutes was:

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

  1. 94 mm of Hg

  2. 47 mm of Hg

  3. 43 mm of Hg

  4. 90 mm of Hg

Show answer
Correct Option: B
Explanation:

                    $A \to 2B + C$

$at\,t = 0$   $x$       $0$    $0$

$at\,t = 10$    $x-y$           $2y$    $y$  

 $total=x-y+2y+y$

        $=x+2y=176\,mm$-------$(i)$

$at\,{t={100}}$   $0$       $2x$    $x$

$total=2x+x=270\,mm$

$ \Rightarrow 3x = 270$
$ \Rightarrow x = 90\,mm\,\,of\,Hg$

put the value of $A$ in $e{q^n}\,(i),$ we get
   $x+2y=176$
$ \Rightarrow 90 + 2y = 176$
$ \Rightarrow  2y = 86$
$ \Rightarrow y=43\,\,\,mm\,\,of\,Hg$

At the end of $10$ min pessure of $A$ is  $x-y=90-43=47\,mm\,of\,Hg$

Option B is correct.

If you have a solution in equilibrium containing $Cl^-$ ions and you added $NaCl$ to the solution, what is going to happen?

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

  1. The reaction will shift to the left to compensate for the increased concentration of $Cl^-$ ions

  2. The reaction will become unbalanced and stay unbalanced

  3. Le Chatelier's principle says that nothing will happen

  4. More $Na^+$ ions will be made so that concentrations of $Na^+$ and $Cl^-$ even out

  5. Equilibrium will be restored

Show answer
Correct Option: A
Explanation:

If you have a solution in equilibrium containing $Cl^-$ ions and you added $NaCl$ to the solution, the reaction will shift to the left to compensate for the increased concentration of $Cl^-$ ions. This is in accordance with the  Le Chatelier's Principle .
The Le Chatelier's Principle states that any change in a substance on one side of the equation, either in concentration, temperature, pressure or volume, results in an equilibrium shift to oppose the change until a new equilibrium is reached.

Which is the following are true about the chemical equilibrium?

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

  1. The chemical equilibrium is a state in which the rate of the forward reaction is equal to the rate of the reverse reaction.

  2. The chemical equilibrium takes at least 10 hours to be established.

  3. The chemical equilibrium is a state in which the rate of the forward reaction is not equal to the rate of the reverse reaction.

  4. The chemical equilibrium can only occur at temperatures above room temperature.

  5. None of these answers are correct

Show answer
Correct Option: A
Explanation:

The following is true about the chemical equilibrium.
The chemical equilibrium is a state in which the rate of the forward reaction is equal to the rate of the reverse reaction. A chemical equilibrium is a state of balance in a reaction where the forward and reverse reaction speed is equal and the concentrations of the products and reactants remain unchanged.