Tag: introduction to equilibrium

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

$4g \,H _2$ 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:

  1. $3.25$
  2. $1.75$
  3. $2.25$
  4. $2.5$
Reveal answer Fill a bubble to check yourself
D Correct answer
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,
$=\left(2-\cfrac {0.05}{2}\right)+\left(0.5-\cfrac {0.05}{2}\right)+0.05$
$=2.5$

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

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:

  1. Adding a suitable catalyst

  2. Adding an inert gas

  3. Decreasing the volume of container
  4. Increasing the amount of $CO(g)$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $CO _2$.

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

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 ?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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_______.

  1. PCl$ _5$ will remain unchanged
  2. Cl$ _2$ will be greater
  3. PCl$ _5$ will become less
  4. PCl$ _5$ will become greater
Reveal answer Fill a bubble to check yourself
C Correct answer
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$.

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

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:

  1. $[AB _3] _{eq} = [BC] _{eq}$
  2. $[AB _2] _{eq} = [B _2C] _{eq}$
  3. $[AB _3] _{eq} > [B _3C _2] _{eq}$
  4. $[AB _3] _{eq} > [BC] _{eq}$
Reveal answer Fill a bubble to check yourself
C,D Correct answer
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  $[AB _3] _{eq}  >  [BC] _{eq}$

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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:

  1. 94 mm of Hg

  2. 47 mm of Hg

  3. 43 mm of Hg

  4. 90 mm of Hg
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Which is the following are true about the chemical equilibrium?

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.