Acids, Bases And Salts Test

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Acids, Bases And Salts Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following acids is present in ant sting?

A
Oxalic acid

B
Methanoic acid

C
Acetic acid

D
Sulphuric acid

Solution

Methanoic acid, also called formic acid, is present in the sting of ants and honey bees.
Question 2
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Which of the following solutions can be used to remove the odour of onion from a strip of cloth?

A
Dil. HCl

B
Dil. NaOH

C
Conc. H₂SO₄

D
Conc. HNO₃

Solution

Dipping the strip in dil. NaOH would help to get rid of the odour.
Therefore, onion juice is used as an olfactory indicator since it loses its odour with bases but retains it with acids.
Question 3
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Which of the following statements about acids are correct?

I. Bronsted acids are proton donors.
II. Arrhenius acids furnish hydronium ions in their aqueous solutions.
III. All Arrhenius acids are also Bronsted acids.
IV. All Bronsted acids are also Arrhenius acids.

A
I and II

B
II and IV

C
I, II and III

D
II, III and IV

Solution

By the Lowry-Bronsted concept, acids are proton donors.
By the Arrhenius concept also acids are protons donors, but the concept is limited to aqueous solutions.
Therefore, every Arrhenius acid is also a Bronsted acid.
However, every Bronsted acid need not be an Arrhenius acid.
Hence, statement IV is incorrect.
Question 4
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Which of the following reactions are not likely to yield H₂ gas as one of the products?

I. II.
III.
IV.

A
I and II

B
I and IV

C
II and III

D
II and IV

Solution

In case of I, Cu being less electropositive than hydrogen cannot displace it from the acids to produce hydrogen gas.
In case of IV, the displacement will occur, but the hydrogen gas formed will be oxidised to water by HNO₃, which is a strong oxidising agent.
Question 5
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Analyse the two statements given below and select the correct option.

Statement I: When the free ends of a tester are dipped in solutions containing dilute solutions of HCl and CH₃COOH turnwise, the bulb lights up more brightly in the first case.
Statement II: HCl is a stronger acid than CH₃COOH.

A
Both statements I and II are correct and statement II is the correct reason for I.

B
Both statements I and II are correct but statement II is not the correct reason for I.

C
Statement I is correct but statement II is incorrect.

D
Both statements I and II are incorrect.

Solution

HCl is a strong acid (strong electrolyte) and dissociates completely in its aqueous solution, whereas CH₃COOH being a weak acid (weak electrolyte) dissociates partially. Hence, the aqueous solution of HCl contains more ions and has a greater conductivity.
Therefore, option (1) is correct.
Question 6
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The decomposition of sodium hydrogen carbonate finds its application

A. in preparation of baking powder
B. in fire extinguishers
C. as antacid
D. in fireworks

A
Both A and B

B
Both A and C

C
A, B and C

D
A, B, C and D

Solution

Sodium bicarbonate is used as baking soda.
2NaHCO₃(s) Na₂CO₃(s) + H₂O(g) + CO₂(g)
The carbon dioxide evolved helps in the aeration of the dough and facilitates the baking action.
However it is used in combination with tartaric acid which neutralizes the base formed to avoid a bitter taste to the dish.
This combination of baking soda and tartaric acid is called baking powder. Hence A is correct.

In soda fire extinguishers it produces carbon dioxide by the following reaction:

The CO₂ formed envelops the burning substance to cut off the supply of oxygen helps to extinguish the fire. Hence, B is correct.

NaHCO₃ is used as an antacid as it neutralizes the excess acid in the stomach by the following reaction.

Hence, C is correct.

Sodium bicarbonate is one of the main components of the common black snake firework. The effect is caused by the thermal decomposition, which produces carbon dioxide gas to produce a long snake-like ash as a combustion product. Therefore, D is correct.
Hence, all A, B, C and D are correct.
Question 7
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Which of the acids given below is monobasic?

A
CH₃COOH

B
H₂SO₄

C
H₃PO₄

D
H₂SO₃

Solution

Acetic acid is monobasic acid, and one mole of the acid will produce one mole of H⁺ ions in its aqueous solution.

While H₂SO₄ and H₂SO₃ are dibasic and H₃PO₄ is tribasic in nature.
Question 8
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According to Arrhenius concept, a base is a substance that furnishes the anion of the solvent (water). On the basis of this concept, which one of the following can be categorised as a base?

A
CaO

B
CO₂

C
SO₃

D
HCl

Solution

CaO (s) + H₂O (l) Ca(OH)₂ (aq)

Ca(OH)₂ Ca⁺² (aq) + 2OH^-(aq)
Question 9
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Which among the following is not an alkali?

A
NaOH

B
KOH

C
Ca(OH)₂

D
Cu(OH)₂

Solution

An alkali is a water-soluble base. Among the given options, Cu(OH)₂ is not an alkali.
Question 10
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Directions: In the following question, two statements are given, one labelled as Assertion and the other as Reason. Examine both the statements carefully and mark the correct answer accordingly.

Assertion (A): The flowers of Hydrangea plant turn pink in the presence of potassium hydroxide.
Reason (R): The flowers of Hydrangea plant are usually pink, which turn blue in the presence of a base.

A
A is incorrect, but R is correct.

B
Both A and R are correct and R is the correct explanation for A.

C
A is correct, but R is incorrect.

D
Both A and R are incorrect.

Solution

Hydrangea flowers can act as a natural indicator and their colour depends on the pH of the soil. It is pink in basic soil and blue in acidic soil. Therefore, the statement A that the colour of the flower is pink in the presence of a base (KOH) is true.
However, the second statement (R) is false.
Question 11
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There are two test tubes - A and B. Test tube A contains dilute hydrochloric acid and test tube B contains dilute sodium hydroxide. The two samples are tested with various indicators. Which of the following statements is true?

A
The solution in test tube A gives pink colour with phenolphthalein, but the solution in test tube B is colourless.

B
When clove oil is added to the sample, test tube B does not smell of clove oil.

C
Solutions in test tubes A and B both give green colour with universal indicator.

D
Solution in test tube A gives yellow colour with methyl orange, while solution in test tube B gives pink colour.

Solution

Clove oil is an olfactory indicator and it loses its odour with bases, but retains it with acids.
The other options are wrong because of the following reasons:
(1) Phenolphthalein is colourless with acids (test tube A) and pink with bases (test tube B).
(3) With the universal indicator, the acid in test tube A will turn red and the base in test tube B will turn blue.
(4) Methyl orange gives pink colour with acids (test tube A) and blue colour with bases (test tube B).
Question 12
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A Lewis acid is usually an electron deficient species which can accept a pair of electrons and form a coordinate bond. The Lewis acid among the following is

A
BF₃

B
NH₃

C
PH₃

D
H₂O

Solution

BF₃ is electron deficient as its octet is not complete. Hence, it is a Lewis acid.
Question 13
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NH₃ has a lone pair of electrons on nitrogen and hence, it can be categorised as a/an

A
Arrhenius base

B
Arrhenius acid

C
Lewis base

D
Lewis acid

Solution

A Lewis base is an electron rich species, which may be negatively charged or electron rich due to the presence of a lone pair of electrons. For example: NH₃.
Question 14
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The effervescence produced on the addition of a metal to an aqueous solution of hydrogen carbonate is due to the evolution of

A
H₂

B
CO

C
CO₂

D
O₂

Solution

Metal + Hydrogen carbonate Salt + Carbon dioxide + Water
Question 15
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The reaction of zinc granules with aqueous NaOH produces

A
Na(Zn)₂OH

B
NaZnO₂ + H₂

C
Na₂ZnO₂ + H₂

D
Na + Zn(OH)₂

Solution

Zinc reacts with NaOH to produce a soluble complex sodium zincate and hydrogen gas.

Zn + 2NaOH Na₂ZnO₂ + H₂
Question 16
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If a few drops of a concentrated acid accidentally spill over the hand of a student, what should he do?

A
Wash the hand with saline water

B
Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate

C
After washing with plenty of water, apply the solution of sodium hydroxide to the hand

D
Neutralise the acid with a strong alkali

Solution

The harmful effect of an acid can be neutralised by a base, however, the base used should be mild, because a strong alkali, like NaOH, can be highly corrosive on the skin.
Question 17
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Which among the following has the greatest concentration of H⁺ ions?

A
1 mol L^-1 HCl solution

B
1 mol L^-1 H₃PO₂ solution

C
1 mol L^-1 H₂SO₄ solution

D
1 mol L^-1 H₂CO₃ solution

Solution

Concentrations of all the solutions are equal, and HCl and H₃PO₂ are monobasic. Both H₂CO₃ and H₂SO₄ are dibasic, but H₂CO₃is a weak acid, whereas H₂SO₄ is a strong acid. Therefore, due to double dissociation of H₂SO₄, it will give the greatest concentration of H⁺ions.
Question 18
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Which of the following pairs of compounds cannot co-exist in water?

A
NaHCO₃ and Na₂CO₃

B
Na₂CO₃ and NaOH

C
NaHCO₃ and NaOH

D
NaHCO₃ and NaCl

Solution

Sodium bicarbonate is an acidic salt and it will react with NaOH (base) as follows:

NaHCO₃ (aq) + NaOH (aq) Na₂CO₃ (aq) + H₂O (l)
Question 19
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The pH of 10^-6M KOH is

A
6

B
0.6

C
8

D
0.8

Solution

pOH of 10^-6M solution of KOH = -log 10^-6 = 6
Therefore, pH = 14 - 6 = 8.
Moreover, KOH is a base and will have pH > 7.
Question 20
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Which of the following solutions has the lowest pH value?

A
0.1 Molar NaCl solution

B
0.01 Molar NaHCO₃ solution

C
0.001 Molar Na₂CO₃ solution

D
0.01 Molar NaOH solution

Solution

NaHCO₃ is an acidic salt and its solution will have pH < 7.
NaCl is a neutral salt and its solution will have pH = 7.
Na₂CO₃ is a basic salt and its solution will have pH > 7.
NaOH is a base and its solution will have pH > 7.