Equilibrium Test

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Equilibrium Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

Which buffer solution comprising of the following has its $$pH$$ value greater than 7?

A
$${ CH }_{ 3 }COOH$$+$${ CH }_{ 3 }COONa$$

B
$$HCOOH + HCOOK$$

C
$${ CH }_{ 3 }COO{ NH }_{ 4 }$$

D
$${ NH }_{ 4 }OH+{ NH }_{ 4 }Cl$$

Solution

The $$pH$$ value of a basic buffer is always greater than $$7.$$
Among the given options, $$NH_4OH+NH_4Cl$$ is the only mixture which consists of a mixture of a weak base and its conjugated salt and thus, has a $$pH$$ greater than 7.

Hence, option $$D$$ is correct.
Question 2
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Protons ( $$H^+$$ ions ) are found when a substance is dissolved in water. The substance is ___________.

A
$$KOH$$

B
$$NaH$$

C
$$H_{2}SO_{4}$$

D
$$NH_{3}$$

E
$$CH_{4}$$

Solution

An acid is a proton $$ (H^+)$$ donor. A base is a proton (hydrogen ion) acceptor. Acids dissociate into $$H^+$$ ions in water. The acid $$H_2SO_4$$ dissociates into $$H^+$$ and $$SO_4^{2-}$$ will show the presence of $$H^+$$ even after they dissolve in water. $$KOH$$ gives $$OH^-$$ ion.
$$NaH$$ gives $$H^-$$ ions while $$NH_3$$ is also a base forms $$NH_4^+$$ in water. $$CH_4$$ is not react as acid nor like a base.
Question 3
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Which among the following resists a rapid change of pH?

A
Buffer

B
Indicator

C
Arrhenius acid

D
Arrhenius base

E
Neutral condition

Solution

A Buffer solution resists a rapid change of pH.
A Buffer solution is a mixture of weak acid and its salt with strong base (or a mixture of weak base and its salt with strong acid). When a small amount of an acid or a base is added to a buffer solution, it resists change of pH.
Question 4
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Addition of water to $$X$$ solution will not change concentration of $$H_{3}O^{+}$$. $$X$$ is:

A
chemical pH indicator

B
acid/base buffer

C
anhydrous solution

D
hypotonic solution

E
supersaturated solution

Solution

Addition of water to $$X$$ solution does not change the $$pH$$ of the solution, which means the concentration of the species present changes in such a way that the $$pH$$ remains the same. This is possible for acid/base buffer.
$$pH=pk_a+\log \cfrac{[salt]}{[acid]}$$
Since the volume changes the same for both salt and acid, the ratio $$\cfrac{[salt]}{[acid]}$$ remains the same and hence $$pH$$ also remains the same. Same in the case of basic buffer solution.
Question 5
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Assertion: $$NaCl(aq)$$ is an electrolyte.
Reason: It forms ions in solution.

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

pure water is a very good insulator, but if we add sodium chloride we create ions to form an electrolytic solution.
$$NaCl(s) + H_2O(l) \longrightarrow Na^+(aq) + Cl^-(aq) + H_2O(l)$$
Therefore, $$NaCl$$ is an electrolyte.
Question 6
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$$\displaystyle { H }_{ 2 }O+{ H }_{ 2 }O\rightleftharpoons { H }_{ 3 }{ O }^{ + }+{ OH }^{ - }$$
The above reverse reaction is an exothermic reaction. What will happen if the temperature is lowered?

A
The $$\displaystyle pH$$ will decrease.

B
The equilibrium will shift to the right.

C
The concentration of $$\displaystyle { H }_{ 3 }{ O }^{ + }$$ ions will increase.

D
The equilibrium will shift to the left.

E
Temperature does not affect equilibrium.

Solution

Since the forward reaction is exothermic, lowering the temperature will shift the equilibrium in a direction that counteracts this change.
Hence by decreasing the temperature, the reaction will proceed in that direction which will produce more heat.
Thus, a reaction will proceed in the exothermic direction that is the in the direction of the forward reaction i.e. towards the right.
Question 7
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The Haber process is used for producing ammonia from nitrogen and hydrogen. This reaction could be forced to produce more ammonia by :

A
Increasing the reaction pressure

B
Decreasing the reaction pressure

C
Adding a catalyst

D
Both b and c

E
None of the above

Solution

The catalyst has no effect whatsoever on the position of the equilibrium. Adding a catalyst doesn't produce any greater percentage of ammonia in the equilibrium mixture. Its only function is to speed up the reaction.
Question 8
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__________ can be shifted by adding more reactants.

A
The point of equilibrium

B
The triple point

C
The freezing point

D
The point where reactants first form products

E
The boiling point

Solution
Question 9
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What does a buffer do?

A
It keeps the $$pH$$ of a solution from changing very much.

B
It maintains the equilibrium of a reaction.

C
It maintains the amount of acid in a solution

D
It maintains the amount of base in a solution

E
It keeps the $$pH$$ of a solution from changing at all.

Solution

A buffer keeps the $$pH$$ of a solution from changing very much.
A buffer is a solution that contains equal amounts of a weak acid and its conjugate base, or a weak base and its conjugate acid.
Such solution resists the change in $$pH$$ when a small amount of an acid or a base is added.
For example, a mixture of acetic acid and sodium acetate acts as an acid buffer solution. Similarly, a mixture of ammonium hydroxide and ammonium chloride is a basic buffer solution.
Question 10
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What is the relationship between $$[OH^-]$$ and $$[H_3O^+]$$ in a water solution?

A
When multiplied together, they equal a constant, $$K_w$$.

B
When multiplied together, they equal each other.

C
When divided, they equal a constant, $$K_w$$.

D
When one increases, the other increases.

E
They explain the acidity of a solution.

Solution

When $$[OH^-]$$ and $$[H_3O^+]$$ (in a water solution) are multiplied together, they equal a constant, $$K_w$$ which is ionic product of water with a value of $$\displaystyle 1 \times 10^{-14}$$ at $$\displaystyle 25^oC$$.

Hence, the correct option is A.

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Re-Attempt Weekly Quiz Competition

Equilibrium Test - 28

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Equilibrium Test - 28

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Question 1

$${ CH }_{ 3 }COOH$$+$${ CH }_{ 3 }COONa$$

$$HCOOH + HCOOK$$

$${ CH }_{ 3 }COO{ NH }_{ 4 }$$

$${ NH }_{ 4 }OH+{ NH }_{ 4 }Cl$$

Solution

Question 2

$$KOH$$

$$NaH$$

$$H_{2}SO_{4}$$

$$NH_{3}$$

$$CH_{4}$$

Solution

Question 3

Buffer

Indicator

Arrhenius acid

Arrhenius base

Neutral condition

Solution

Question 4

chemical pH indicator

acid/base buffer

anhydrous solution

hypotonic solution

supersaturated solution

Solution

Question 5

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 6

The $$\displaystyle pH$$ will decrease.

The equilibrium will shift to the right.

The concentration of $$\displaystyle { H }_{ 3 }{ O }^{ + }$$ ions will increase.

The equilibrium will shift to the left.

Temperature does not affect equilibrium.

Solution

Question 7

Increasing the reaction pressure

Decreasing the reaction pressure

Adding a catalyst

Both b and c

None of the above

Solution

Question 8

The point of equilibrium

The triple point

The freezing point

The point where reactants first form products

The boiling point

Solution

Question 9

It keeps the $$pH$$ of a solution from changing very much.

It maintains the equilibrium of a reaction.

It maintains the amount of acid in a solution

It maintains the amount of base in a solution

It keeps the $$pH$$ of a solution from changing at all.

Solution

Question 10

When multiplied together, they equal a constant, $$K_w$$.

When multiplied together, they equal each other.

When divided, they equal a constant, $$K_w$$.

When one increases, the other increases.

They explain the acidity of a solution.

Solution

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