Equilibrium Test

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Equilibrium Test - 22

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following will supress the ionisation of acetic acid in aqueous solution?

A
$$NaCl$$

B
$$HCI$$

C
$$KCI$$

D
Unpredicatble

Solution

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.
So addition of $$CH_3COONa$$ to $$CH_3COOH$$ increases the $$pH$$ of solution but addition of $$NH_4Cl$$ to $$NH_4OH$$ decreases the $$pH$$ of solution.
Here, the addition of $$HCl$$ acid will suppress the ionisation of acetic acid.
Question 2
1 / -0

The equilibrium $$SO_2Cl_2(g)\rightleftharpoons SO_2(g)+Cl_2(g)$$ is attained at $$25^oC$$ in a closed container and an inert gas, helium, is introduced. Which of the following statements is/are correct?

A
The concentrations of $$SO_2,Cl_2$$,and $$SO_2Cl_2$$ change.

B
More chlorine is formed

C
The concentration of $$SO_2$$ is reduced

D
All are incorrect

Solution

At constant volume, there is no effect of addition of inert gas to a reaction in equilibrium. At constant pressure, for the reactions for which $$\Delta n = 0$$. there is no effect of addition of inert gas to a reaction in equilibrium. At constant pressure, for the reactions for which $$\Delta n \neq 0$$, the equilibrium shifts in the direction of more number of moles.
Question 3
1 / -0

The solubility of $$AgI$$ in $$NaI$$ solutions is less than that in pure water because:

A
$$AgI$$ forms complex with $$NaI$$

B
of common ion effect

C
solubility product of $$AgI$$ is less than that of $$NaI$$

D
the temperature of the solution decreases

Solution

$$AgI \rightleftharpoons Ag^+ + I^-$$
$$NaCl \rightarrow Na^+ + I^-$$
Sodium iodide is a strong electrolyte and is completely dissociated. This increases the iodide ion concentration in solution and suppresses the ionization of $$AgI$$. Hence, the solubility of $$AgI$$ decreases.
This is called common ion effect.
Question 4
1 / -0

For the reaction $$H_2(g) + I_2(g)\rightleftharpoons 2HI(g)$$ The equilibrium constant $$K_p$$ changes with :

A
Total pressure

B
Catalyst

C
The amounts of $$H_2$$ and $$I_2$$ present

D
Temperature

Solution

The equilibrium constant does not change at all with changes in concentrations, volume, pressure, presence of catalyst, etc. It changes only with changes in temperature of the system. For endothermic reaction, the value of K increases with increase in temperature and vice versa. For exothermic reaction, the value of K decreases with increase in temperature and vice versa.
Question 5
1 / -0

$$pOH$$ of water is $$7.0$$ at $$298 K$$. If water is heated to $$350 K$$, which of the following should be true?

A
$$pOH$$ will decrease

B
$$pOH$$ will increase

C
$$pOH$$ will remain seven

D
Concentration of $$H^{\oplus}$$ ions will increae but that of $$\overset{\circleddash}{O}H$$ will decrease.

Solution

As we increase the temp. more water molecules will dissociate and the solution will have more no of hydrogen ion as well as hydroxide ion.
As a result, both $$pH$$ and $$pOH$$ of solution will decrease.
Question 6
1 / -0

In the third group of qualitative analysis, the precipatitating reagent is $$NH_4Cl / NH_4OH$$. The function of $$NH_4Cl$$ is to

A
increase the ionisation of $$NH_4OH$$

B
supress the ionisation of $$NH_4OH$$

C
convert the ions of group third into their respective chlorides

D
stabilise the hydroxides of group $$III$$ cations

Solution

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.
So, addition of $$CH_3COONa$$ to $$CH_3COOH$$ increases the pH of solution but addition of $$NH_4Cl$$ to $$NH_4OH$$ decreases the pH of solution.
So, the function of $$NH_4Cl$$ to suppress the ionisation of $$NH_4OH$$ and to reduce conentration of hydroxide ion in solution.
Question 7
1 / -0

When solid $$KCl$$ is added to a saturated solution of $$AgCI$$ in $$H_2O$$

A
Nothing happens

B
Solubility of $$AgCl$$ decreases

C
Solubility of $$AgCl$$ increases

D
Solubility product of $$AgCl$$ increases

Solution

$$AgCl \rightleftharpoons Ag^+ + Cl^-$$
$$KCl \rightarrow K^+ + Cl^-$$
Potassium chloride is a strong electrolyte and is completely dissociated. This increases the chloride ion concentration in solution and suppresses the ionization of $$AgCl$$. Hence, the solubility of $$AgCl$$ decreases.
Question 8
1 / -0

Pure ammonia is placed in a vessel at a temperature where its dissociation constant $$(\alpha)$$ is appreciable. At equilibrium :

A
$$K_p$$ does not change significantly with pressure

B
$$\alpha$$ does not change with pressure

C
The concentration of $$NH_3$$ does not change with pressure

D
The concentration of hydrogen is less than that of nitrogen

Solution

The equilibrium constant does not change at all with changes in concentrations, volume, pressure, presence of catalyst, etc. It changes only with changes in temperature of the system. For endothermic reaction, the value of K increases with increase in temperature and vice versa. For exothermic reaction, the value of K decreases with increase in temperature and vice versa.
Question 9
1 / -0

Buffer solutions can be prepared from mixtures of:

A
$$HCl$$ and $$NaCl$$

B
$$NaH_2PO_4$$ and $$Na_2HPO_4$$

C
$$CH_3COOH + NaCl$$

D
$$NH_3OH+NH_3$$

Solution

A solution that resists change in pH value upon addition of a small amount of strong acid or base (less than 1 %) or when the solution is diluted is called buffer solution.
Basic buffer solution: A basic buffer solution consists of a mixture of a weak base and its salt with strong acid.
Acidic buffer solution: An acidic buffer solution consists of a solution of a weak acid and its salt with a strong base.
So among given options, $$NaH_2PO_4 + Na_2HPO_4$$ will form a buffer solution.
Question 10
1 / -0

The $$pH$$ of a dilute solution of acetic acid was found to be $$4.3$$ The addition of a small crystal of sodium acetate will cause $$pH$$ to:

A
become less than $$4.3$$

B
become more than $$4.3$$

C
remain equal to $$4.3$$

D
unpredictable

Solution

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.
Due to this common ion effect, when we add sodium acetate dissociation of acetic acid decreases and solution will have less number of hydrogen ion and so, pH increases. (as $$pH = -log [H^+]$$)

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Equilibrium Test - 22

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Equilibrium Test - 22

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Question 1

$$NaCl$$

$$HCI$$

$$KCI$$

Unpredicatble

Solution

Question 2

The concentrations of $$SO_2,Cl_2$$,and $$SO_2Cl_2$$ change.

More chlorine is formed

The concentration of $$SO_2$$ is reduced

All are incorrect

Solution

Question 3

$$AgI$$ forms complex with $$NaI$$

of common ion effect

solubility product of $$AgI$$ is less than that of $$NaI$$

the temperature of the solution decreases

Solution

Question 4

Total pressure

Catalyst

The amounts of $$H_2$$ and $$I_2$$ present

Temperature

Solution

Question 5

$$pOH$$ will decrease

$$pOH$$ will increase

$$pOH$$ will remain seven

Concentration of $$H^{\oplus}$$ ions will increae but that of $$\overset{\circleddash}{O}H$$ will decrease.

Solution

Question 6

increase the ionisation of $$NH_4OH$$

supress the ionisation of $$NH_4OH$$

convert the ions of group third into their respective chlorides

stabilise the hydroxides of group $$III$$ cations

Solution

Question 7

Nothing happens

Solubility of $$AgCl$$ decreases

Solubility of $$AgCl$$ increases

Solubility product of $$AgCl$$ increases

Solution

Question 8

$$K_p$$ does not change significantly with pressure

$$\alpha$$ does not change with pressure

The concentration of $$NH_3$$ does not change with pressure

The concentration of hydrogen is less than that of nitrogen

Solution

Question 9

$$HCl$$ and $$NaCl$$

$$NaH_2PO_4$$ and $$Na_2HPO_4$$

$$CH_3COOH + NaCl$$

$$NH_3OH+NH_3$$

Solution

Question 10

become less than $$4.3$$

become more than $$4.3$$

remain equal to $$4.3$$

unpredictable

Solution

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