Equilibrium Test

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Equilibrium Test - 52

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Question 1
1 / -0

Which factor, when decreased will cause a reaction to proceed more quickly?

A
Exothermic

B
Particle Size

C
Endothermic

D
Catalyst

E
Concentration

Solution

By van't Hoff equation,
$$\dfrac { dlnk }{ dT } =\dfrac { { \triangle H }^{ 0 } }{ { RT }^{ 2 } } $$
Now, if $${ \triangle H }^{ 0 }>0$$ (endothermic reaction), $$\dfrac { dlnk }{ dT } =+ve$$. So, $$Kp$$ increases with increase of temperature. So, for exothermic reactions, it will decrease with increase of temperature. So, to proceed the reaction more quickly, exothermic nature of the reaction should be decreased. These observations can also be predicated by Le-chatclier's principle.
Question 2
1 / -0

What happens when a chemical reaction system is stressed by an 'increase in the concentration of the reactants?

A
The system shifts to the right toward products.

B
The system shifts to the left toward reactants.

C
The system shifts to the right toward reactants.

D
The system shifts to the left toward products.

E
The system remains unchanged.

Solution

When a chemical reaction system is stressed by an 'increase in the concentration of the reactants, the system shifts to the right toward products.
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.
For example when the reactant concentration is increased, the equilibrium will shift in the forward direction so that more and more reactants will react. This will decrease the reactant concentration.
Question 3
1 / -0

Equilibrium constant for the reaction, $$NH_{4}OH + H^{+}\rightleftharpoons NH_{4}^{+} + H_{2}O$$ is $$1.8\times 10^{9}$$. Hence, equilibrium constant for $$NH_{3}(aq) + H_{2}O \rightleftharpoons NH_{4}^{+} + OH^{-}$$ is:

A
$$1.8\times 10^{-5}$$

B
$$1.8\times 10^{5}$$

C
$$1.8\times 10^{-9}$$

D
$$5.59\times 10^{-10}$$

Solution

$$NH_{4}OH + H^{+}\rightleftharpoons NH_{4}^{+} + H_{2}O$$

$$\therefore \dfrac {[NH_{4}^{+}][H_{2}O]}{[NH_{4}OH][H^{+}]} = 1.8\times 10^{9}$$

Again,
$$NH_{3} + H_{2}O\rightarrow NH_{4}OH \rightleftharpoons NH_{4}^{+} + OH^{-}$$

$$\therefore K' =\dfrac {[NH_{4}^{+}][OH^{-}]}{[NH_{4}OH]}$$

Now $$\dfrac {K'}{K} = \dfrac {[NH_{4}^{+}][OH^{-}]}{[NH_{4}OH]}\times \dfrac {[NH_{4}OH][H^{+}]}{[NH_{4}^{+}][H_{2}O]}$$

$$= [OH^{-}][H^{+}] (\because H_{2}O$$ is in excess)

$$= K_{w} = 1\times 10^{-14}$$

$$\therefore K' = K\times 1\times 10^{-14}$$

$$= 1.8\times 10^{9} \times 10^{-14} = 1.8\times 10^{-5}$$
Question 4
1 / -0

Given the reaction $$2A(g) + B(g) + heat \rightleftharpoons 3C(g) + D(g)$$, what could be done to the reaction to shift the equilibrium so that more $$D$$ is made?

A
Increase the concentration of $$D$$

B
Increase the concentration of $$C$$

C
Increase the temperature

D
Increase the pressure

E
Remove $$B$$ from the reaction

Solution

To shift the equilibrium so that more $$D$$ is made, increase the temperature.
Since the term heat is on reactant sides, the reaction is endothermic. Heat is absorbed during forward reaction. When temperature is increased, the equilibrium will shift in the forward direction so that more and more heat is absorbed. This will minimize the effect of increase in temperature.
Question 5
1 / -0

Which of the following will form a buffer solution of 1L solution?

A
0.2 mol of $$\displaystyle HCl$$ and 0.1 mole of $$\displaystyle { K }_{ 2 }{ SO }_{ 3 }$$

B
0.2 mol of $$\displaystyle NaOH$$ and 0.4 mol of $$\displaystyle HF$$

C
0.1 mol of $$\displaystyle HBr$$ and 0.1 mol of $$\displaystyle { Ba\left( OH \right) }_{ 2 }$$

D
0.4 mol of $$\displaystyle HCl$$ and 0.2 mol of $$\displaystyle { NH }_{ 3 }$$

E
0.2 mol of $$\displaystyle NaOH$$ and 0.4 mol of $$\displaystyle HCl$$

Solution

The following will form a buffer solution of $$1\ L$$ solution.
$$0.2$$ mol of $$NaOH$$ and $$0.4$$ mol of $$HF$$:
It is an example of acid buffer solution. An acid buffer solution contains a weak acid and its salt with a strong base.
$$0.2$$ mol of $$NaOH$$ will react with $$0.2$$ mol of $$HF$$ to form $$0.2$$ mol of $$NaF$$.
$$0.2$$ mol of $$HF$$ will remain.
Thus, the mixture contains $$0.2$$ mol of $$HF$$ and $$0.2$$ mol of $$NaF$$.
Question 6
1 / -0

For a reaction if $$K_p > K_c$$, the forward reaction is favoured by:

A
low pressure

B
high pressure

C
high temperature

D
low temperature

Solution

For a reaction if $$K_p>K_c$$, the forward reaction is favoured by low pressure.

$$K_p = K_c (RT)^{\Delta n}$$

Since $$K_p>K_c $$

$$\therefore \Delta n>0$$, i.e. product side contains more particles than the reactant side.

At low pressure, the equilibrium will shift in the forward direction so that more and more gaseous products are formed. This will increase the total pressure and nullify the effect of low pressure.
Question 7
1 / -0

Very strong acids, such as $$HNO_3$$ and $$HCl$$, appear to be equally strong in water. This "leveling effect" of water is because

A
$$OH^-$$ is a stronger base than the conjugate bases of $$HNO_3$$ and $$HCl$$

B
$$H_3O^+$$ is a stronger acid than $$HNO_3$$ and $$HCl$$

C
$$H_2O$$ is a stronger base than the conjugate bases of $$HNO_3$$ and $$HCl$$

D
$$H_2O$$ is a weaker base than the conjugate bases of $$HNO_3$$ and $$HCl$$

Solution

Very strong acids, such as $$\displaystyle HNO_3$$ and $$\displaystyle HCl$$, appear to be equally strong in the water. This "leveling effect" of water is because $$\displaystyle H_2O$$ is a stronger base than the conjugate bases of $$\displaystyle HNO_3$$ and $$\displaystyle HCl$$.

Hence, option (C) is the correct answer.

Note: When a strong acid is dissolved in water, it reacts with water to form hydronium ion $$\displaystyle (H_3O^+)$$.

$$\displaystyle HCl + H_2O \rightarrow H_3O^+ + Cl^-$$
Question 8
1 / -0

Assertion: When a non-volatile solute is added to pure water, the vapor pressure of the water will decrease.
Reason: All solutes dissociate into positive and negative ions.

A
Both Assertion and Reason are true and Reason is the correct explanation of Assertion

B
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

C
Assertion is true but Reason is false

D
Assertion is false but Reason is true

E
Both Assertion and Reason are false

Solution

Vapor pressure is a measurement of the likelihood of the molecules of a pure solvent to change from the liquid to the vapor phase. If we add a non volatile solute to solvent such as water, we decrease the tendency for water molecules to evaporate into the gas phase. In essence, the solute particles obstruct or reduce the likelihood of evaporation.

As a result, fewer molecules change from the liquid to the gas phase, thus reducing the vapor pressure. so Assertion is true.
All solutes do not dissociate into positive and negative ions, so Reason is false.
Question 9
1 / -0

Assertion: Water makes a good buffer.
Reason: A good buffer will resist changes in $$\displaystyle pH$$.

A
Both Assertion and Reason are true and Reason is the correct explanation of Assertion

B
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

C
Assertion is true but Reason is false

D
Assertion is false but Reason is true

E
Both Assertion and Reason are false

Solution

A buffer solution can be defined as a solution which resists a change in its pH when such a change is caused by the addition of a small amount of acid or base.
Buffer solutions can be obtained:
1: by mixing a weak acid with its salt with a strong base, eg; Acetic Acid + Soidum Acetate, Boric acid + Borax, Phthalic acid + Potassium acid phthalate.
2: by mixing a weak base with its salt with a strong acid, e.g; (a) $$NH_4OH + NH_4Cl$$ , (b) Glycine + Glycine hydrochloride.
3: by a solution of ampholyte. The ampholytes or amphoteric electrolytes are the substances which show properties of both an acid and a base. Proteins and amino acids are the examples of such electrolytes.
4: by a mixture of an acid salt and a normal salt of a polybasic acid, e.g., $$Na_2HPO_4 + Na_3PO_4$$, or a salt of weak acid and a weak base, such as $$CH_3COONH_4$$.
Question 10
1 / -0

A litre of solution is saturated with $$AgCl$$. To this solution if $$1.0\times { 10 }^{ -4 }$$ mole of solid $$NaCl$$ is added, what will be the $$\left[ { Ag }^{ + } \right] $$ assuming no volume change?

A
More

B
Less

C
Equal

D
Zero

Solution

A litre of solution is saturated with $$AgCl$$.

To this solution if $$1.0 \times 10^{-4} $$ mole of solid $$NaCl$$ is added, $$\displaystyle [Ag^+]$$ will be less.

$$\displaystyle AgCl \rightleftharpoons Ag^+ + Cl^-$$
$$\displaystyle NaCl \rightarrow Na^+ + Cl^-$$

Thus, the dissociation of $$NaCl$$ provides chloride ions that are common to $$AgCl$$. Due to common ion effect, the dissociation of $$AgCl$$ is suppressed and $$\displaystyle [Ag^+]$$ decreases.

Hence, option B is correct.

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Equilibrium Test - 52

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Equilibrium Test - 52

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Question 1

Exothermic

Particle Size

Endothermic

Catalyst

Concentration

Solution

Question 2

The system shifts to the right toward products.

The system shifts to the left toward reactants.

The system shifts to the right toward reactants.

The system shifts to the left toward products.

The system remains unchanged.

Solution

Question 3

$$1.8\times 10^{-5}$$

$$1.8\times 10^{5}$$

$$1.8\times 10^{-9}$$

$$5.59\times 10^{-10}$$

Solution

Question 4

Increase the concentration of $$D$$

Increase the concentration of $$C$$

Increase the temperature

Increase the pressure

Remove $$B$$ from the reaction

Solution

Question 5

0.2 mol of $$\displaystyle HCl$$ and 0.1 mole of $$\displaystyle { K }_{ 2 }{ SO }_{ 3 }$$

0.2 mol of $$\displaystyle NaOH$$ and 0.4 mol of $$\displaystyle HF$$

0.1 mol of $$\displaystyle HBr$$ and 0.1 mol of $$\displaystyle { Ba\left( OH \right) }_{ 2 }$$

0.4 mol of $$\displaystyle HCl$$ and 0.2 mol of $$\displaystyle { NH }_{ 3 }$$

0.2 mol of $$\displaystyle NaOH$$ and 0.4 mol of $$\displaystyle HCl$$

Solution

Question 6

low pressure

high pressure

high temperature

low temperature

Solution

Question 7

$$OH^-$$ is a stronger base than the conjugate bases of $$HNO_3$$ and $$HCl$$

$$H_3O^+$$ is a stronger acid than $$HNO_3$$ and $$HCl$$

$$H_2O$$ is a stronger base than the conjugate bases of $$HNO_3$$ and $$HCl$$

$$H_2O$$ is a weaker base than the conjugate bases of $$HNO_3$$ and $$HCl$$

Solution

Question 8

Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

Assertion is true but Reason is false

Assertion is false but Reason is true

Both Assertion and Reason are false

Solution

Question 9

Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

Assertion is true but Reason is false

Assertion is false but Reason is true

Both Assertion and Reason are false

Solution

Question 10

More

Less

Equal

Zero

Solution

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