Equilibrium Test

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Equilibrium Test - 11

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Weekly Quiz Competition

Question 1
1 / -0

In aqueous solution, the following mixture acts as buffer :

A
$$H NO_{3} + KN O_{3}$$

B
$$ H_{2}SO_{4} + K_{2}SO_{4}$$

C
$$NH_{4}OH + NH_{4}Cl$$

D
$$CH_{3}COO H+ Na Cl$$

Solution

For buffer solution
Weak acid + Its salt of strong base
OR Weak base + Its salt of strong acid.
In Option C
$$NH_{4}OH \to$$ weak base
$$NH_{4}Cl \to$$ weak base and strong acid salt
Thus option C is right. While no other option follow definition of buffer solution.
Question 2
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The solutions which tend to keep the concentration of hydrogen ions constant, even when small amounts of strong acid or strong base are added to them, are known as:

A
isohydric solutions

B
buffer solutions

C
isotonic solutions

D
neutral solutions

Solution

Buffer solutions have the capacity to react with small amounts of added acid or base without affecting the hydrogen ion concentration of the solution.
Question 3
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Which of the following solution cannot act as a buffer?

A
$$Na H_{2}PO_{4} + H_{3}PO_{4}$$

B
$$CH_{3}COO H+CH_{3}COO Na$$

C
$$H Cl + NH_{4}Cl$$

D
$$ H_{3}PO_{4} + Na_{2} H PO_{4}$$

Solution

A mixture of weak acid and a salt of strong base, or a mixture of weak base and a salt of strong acid acts as a buffer.

$$NaH_2PO_4+H_3PO_4$$ ,$$CH_3COOH+CH_3COONa$$ and $$H_3PO_4+Na_2HPO_4$$ have an acid/salt-base pair.

Therefore they act as a buffer.

A mixture of strong acid and its salt of strong acid don't make an effective buffer.

Therefore, $$HCl+NH_4Cl$$ cannot act as a buffer.

Hence the correct option is C.
Question 4
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Which of the following mixtures in aqueous solution acts as a buffer?

A
$$H NO_{3} + K NO_{3}$$

B
$$ H_{2}SO_{4} + K_{2}SO_{4}$$

C
$$ NH_{4}OH + NH_{4}Cl$$

D
$$CH_{3}COO H + Na Cl$$

Solution

A mixture of ammonium hydroxide and $$HCl$$ react to form ammonium chloride. This also contains unreacted ammonium hydroxide.

$$NH_4OH+HCl \rightarrow NH_4Cl + H_2O$$

Thus, the resulting mixture of $$(NH_4OH+NH_4Cl)$$ is a basic buffer solution. It contains a mixture of weak base ammonium hydroxide and its salt (ammonium chloride) with a strong acid ($$HCl$$).

Option A and B contain strong acid and salt of strong acid and strong base thus it does not form buffer solution,

Option D contains a mixture of weak acid and salt of strong acid and strong base thus it also does not form a buffer solution.
Question 5
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Which can act as buffer?

A
$$NH_{4}Cl + H Cl$$

B
$$CH_{3}COO H+H_{2}CO_{3}$$

C
40 ml of 0.1 M $$NaCN$$+20 ml of 0.1 M $$HCN$$

D
$$NaCl$$+$$NaOH$$

Solution

Buffer solution is a mixture of weak acid and its salt of weak acid.

In Option C
$$NaCN\rightarrow$$ salt of strong base and weak acid

$$HCN \rightarrow$$ weak acid

$$\therefore$$ They can act as buffer.

While no other options follow definition of buffer solution.

Option C is correct.
Question 6
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What will happen when $$CH_{3}COO Na$$ is added to an aqueous solution of $$CH_{3}COO H$$?

A
the pH of the solution decreases

B
the pH of the solution increases

C
the pH of the solution remains unaltered

D
an acidic salt is produced

Solution

$$CH_{3}COOH \leftrightharpoons CH_{3} COO^{-}+H^{+}$$

If $$CH_{3}COONa$$ is added, equilibrium will shift backward due to the common ion effect. $$H^{+}$$ will decrease.

$$\therefore$$ pH will increase.
Question 7
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The number of $$H^{+}$$ ions in $$1\ cc$$ of a solution of $$pH=13$$ is:

A
$$6.023\times 10^{7}$$

B
$$1\times 10^{-13}$$

C
$$6.023\times 10^{13}$$

D
$$1\times 10^{16}$$

Solution

pH 13 means $$[H^+]=10^{-13}$$ M.
Thus, 1 L of solution contains $$10^{-13}$$ moles of hydrogen ions.
Hence, 1 ml or 1 cc of solution will contain $$10^{-13} \times \dfrac {1} {1000}=10^{-16}$$ moles of hydrogen ions.
They corresponds to $$10^{-16} \times 6.023 \times 10^{23}=6.023 \times 10^{7} $$ hydrogen ions.
Question 8
1 / -0

Which of the following statements is true about buffer solution?

A
It keeps the pH value constant in a chemical reaction.

B
It decreases the pH value in a chemical reaction.

C
It increases the pH value in a chemical reaction.

D
It first increases and then decreases the pH value in a chemical reaction.

Solution

Buffer solutions have the capacity to react with small amounts of added acid or base without affecting the hydrogen ion concentration of the solution. Thus, the buffer solutions help to keep the pH value constant in a chemical reaction.
Question 9
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Which of the following solutions can act as buffer?

A
$$0.1$$ molar aq. $$NaCl$$

B
$$0.1$$ molar aq.$$CH_{3}COOH + 0.1$$ molar $$NaOH$$

C
$$0.1$$ molar aq. ammonium acetate

D
$$0.1$$ molar $$H_{3}PO_{4}$$

Solution

Weak acid and salts of a weak acid and weak base and salt of weak base can act as a buffer in the aqueous medium.

0.1 molar aq. ammonium acetate solution is salt of weak base ammonium hydroxide and weak base is ammonium hydroxide.
Thus it forms a buffer solution.

Whereas 0.1 molar aq. NaCl is a salt of strong acid HCl and strong base NaOH, 0.1 molar aq. acetic acid and 0.1 molar NaOH contain strong base NaOH completely neutralised the weak acid. Thus it does not form buffer solution.

And 0.1 molar $$H_3PO_4$$ is a strong acid thus it also does not form buffer solution.

Option C is correct.
Question 10
1 / -0

Which of the following is a buffer solution?

A
$$Na OH +CH_{3}COO Na$$

B
$$Na OH+Na_{2}SO_{4}$$

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

D
$$NH_{4}OH+NH_{4}Cl$$
Solution
Hint- A buffer solution is prepared by mixing an equal amount of weak base and its salt.

Correct option : D

Explanation of correct option:
A buffer solution is a solution which only changes slightly when adding an acid or base to it. It consists of a weak acid and its conjugate base for an acid-buffer solution. It consists of a weak base and its conjugate acid for a basic buffer solution.
Among all given options $$NH_{4}OH+NH_{4}Cl$$ is a combination of weak base $$NH_{4}OH$$ and its salt $$NH_{4}Cl$$, hence, it will act as a buffer solution.

$$NH_4OH+HCl \rightarrow NH_4Cl + H_2O$$

Thus, the resulting mixture $$(NH_4OH+NH_4Cl)$$ is a basic buffer.

Explanation of incorrect options:
$$A$$ is a combination of a strong base and weak acid salt , hence it will not form a buffer solution.
$$B$$ is a combination of a strong base and strong acid-base salt , hence it will not form a buffer solution.
$$C$$ is a combination of strong acid-base salt , hence it will not form a buffer solution.

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Equilibrium Test - 11

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Equilibrium Test - 11

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Question 1

$$H NO_{3} + KN O_{3}$$

$$ H_{2}SO_{4} + K_{2}SO_{4}$$

$$NH_{4}OH + NH_{4}Cl$$

$$CH_{3}COO H+ Na Cl$$

Solution

Question 2

isohydric solutions

buffer solutions

isotonic solutions

neutral solutions

Solution

Question 3

$$Na H_{2}PO_{4} + H_{3}PO_{4}$$

$$CH_{3}COO H+CH_{3}COO Na$$

$$H Cl + NH_{4}Cl$$

$$ H_{3}PO_{4} + Na_{2} H PO_{4}$$

Solution

Question 4

$$H NO_{3} + K NO_{3}$$

$$ H_{2}SO_{4} + K_{2}SO_{4}$$

$$ NH_{4}OH + NH_{4}Cl$$

$$CH_{3}COO H + Na Cl$$

Solution

Question 5

$$NH_{4}Cl + H Cl$$

$$CH_{3}COO H+H_{2}CO_{3}$$

40 ml of 0.1 M $$NaCN$$+20 ml of 0.1 M $$HCN$$

$$NaCl$$+$$NaOH$$

Solution

Question 6

the pH of the solution decreases

the pH of the solution increases

the pH of the solution remains unaltered

an acidic salt is produced

Solution

Question 7

$$6.023\times 10^{7}$$

$$1\times 10^{-13}$$

$$6.023\times 10^{13}$$

$$1\times 10^{16}$$

Solution

Question 8

It keeps the pH value constant in a chemical reaction.

It decreases the pH value in a chemical reaction.

It increases the pH value in a chemical reaction.

It first increases and then decreases the pH value in a chemical reaction.

Solution

Question 9

$$0.1$$ molar aq. $$NaCl$$

$$0.1$$ molar aq.$$CH_{3}COOH + 0.1$$ molar $$NaOH$$

$$0.1$$ molar aq. ammonium acetate

$$0.1$$ molar $$H_{3}PO_{4}$$

Solution

Question 10

$$Na OH +CH_{3}COO Na$$

$$Na OH+Na_{2}SO_{4}$$

$$K_{2}SO_{4} + H_{2}SO_{4}$$

$$NH_{4}OH+NH_{4}Cl$$

Solution

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