Chemistry Previous Year Questions of Acids, Bases and Salts

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Previous Year Questions of Acids, Bases and Salts

Previous Year Questions Of Acids, Bases and Salts

Q 2784101057

Stung by hairs of nettle leaves causes burning pain. This is due to the injection of
NDA Paper 2 2017

(A)

Acetic acid

(B)

Methanoic acid

(C)

Sulphuric acid

(D)

Hydrocholric acid

Solution:

Correct Answer is `=>` (B) Methanoic acid

Q 2158712604

Which one of the following oxides dissolve in water?
NDA Paper 2 2016

(A)

`CuO`

(B)

`Al_2O_3`

(C)

`Fe_(2)O_(3)`

(D)

`Na_(2)O`

Solution:

Sodium oxide `(Na_2O)` is the base anhydride of sodium

hydroxide, when water is added to it, `NaOH` is

produced.

`Na_(2)O + H_(2)O -> 2NaOH`

It is used in ceramics and glasses, though not in a

raw form.

Correct Answer is `=>` (D) `Na_(2)O`

Q 2118434300

Suppose you have four test tubes labelled `A, B, C` and `D`. A contains water, B contains solution of an alkali, C contains solution of an acid, and D contains solution of sodium chloride. Which one of these solutions will turn phenolphthalein solution pink ?
NDA Paper 2 2016

(A)

Solution `A`

(B)

Solution `B`

(C)

Solution `C`

(D)

Solution `D`

Solution:

Solution `B`, i.e. solution of an alkali will turn

phenolphthalein solution pink because

phenolphthalein is a weak organic acid. It turns

colourless in acidic solution and pink in basic solution.

It is a synthetic indicator used in acid-base titrations

Correct Answer is `=>` (B) Solution `B`

Q 1648345203

Match List I with List II and select the correct answer using the codes given below the lists :
NDA Paper 2 2015

(A)

2 3 4 1

(B)

2 4 3 1

(C)

1 4 3 2

(D)

1 3 4 2

Correct Answer is `=>` (B) 2 4 3 1

Q 2232056832

Which one of the following statements is not correct?
NDA Paper 2 2015

(A)

Application of lime makes the soil acidic

(B)

High acidity in soil is typical of humid climate

(C)

Increasing soil acidity results in declining soil fertility

(D)

Arid climate is characterised by alkaline soil

Solution:

The nature of lime is basic. So, when it is added to the soil, it makes it basic. If it is added to the acidic soil, then it's acidity is neutralised by adding lime water.

Correct Answer is `=>` (A) Application of lime makes the soil acidic

Q 1713667549

Which of the following acids is a mineral acid?
NDA Paper 2 2014

(A)

Citric acid

(B)

Hydrochloric acid

(C)

Ascorbic acid

(D)

tartaric acid

Solution:

A mineral acid (or inorganic acid) is an acid

derived from one or more inorganic compounds. All

mineral acids form hydrogen ions and the conjugate base

ions when dissolved in water. Commonly used mineral

acids are sulfuric acid, hydrochloric acid and nitric acid.

Correct Answer is `=>` (B) Hydrochloric acid

Q 1763867745

Which of the following is/are amphoteric?
NDA Paper 2 2014

(A)

`Al(OH)_3 (s)` and `Fe(OH)_3 (s)`

(B)

`Al(OH)_3 (s)` and `HCO_3^(-) (aq)`

(C)

`Ba(OH)_2 (s)` and `NaOH(aq)`

(D)

Only `Al(OH)_3 (s)`

Correct Answer is `=>` (D) Only `Al(OH)_3 (s)`

Q 2356180974

The pH of the solution obtained by dissolving pure sodium chloride in water is
NDA Paper 2 2013

(A)

acidic

(B)

basic

(C)

neutral

(D)

dependent on the amount of sodium chloride dissolved in water

Solution:

The common salt (NaCI) is neutral in nature so, it doesn't change the pH.

Correct Answer is `=>` (C) neutral

Q 2356191074

Turmeric (Haldi) rapidly becomes colourless on addition of
NDA Paper 2 2013

(A)

baking soda

(B)

vinegar

(C)

lemon juice

(D)

alcohol

Solution:

Turmeric (Haldi) rapidly becomes colourless on addition of lemon juice.

Correct Answer is `=>` (C) lemon juice

Q 2326291171

The pH of fresh milk is 6. When it turns sour, the pH.
NDA Paper 2 2013

(A)

becomes < 6

(B)

remains the same, i.e., 6

(C)

becomes > 6

(D)

becomes neutral, i.e., 7

Solution:

The pH of fresh milk is 6. When it turns sour, its pH becomes less than 6 because it becomes acidic in nature.

Correct Answer is `=>` (A) becomes < 6

Q 2327045881

The acid contained in vinegar is.
NDA Paper 2 2013

(A)

Acetic acid

(B)

ascorbic acid

(C)

citric acid

(D)

tartaric acid

Solution:

Vinegar is a liquid consisting mainly of acetic acid `(CH_3CO_2H)` and water. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation process.

Correct Answer is `=>` (A) Acetic acid

Q 2367045885

The acid in gastric juice is
NDA Paper 2 2013

(A)

acetic acid

(B)

nitric acid

(C)

hydrochloric acid

(D)

sulphuric acid

Solution:

Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 .5 to 3.5 and is composed of hydrochloric acid (HCI) and large quantities of potassium chloride (KCI) and sodium chloride (NaCI). The acid plays a key role in digestion of proteins, by activating digestive enzymes and making ingested proteins unravel, so that digestive enzymes breakdown the long chains of amino acids.

Correct Answer is `=>` (C) hydrochloric acid

Q 2337556482

Which one among the following is the correct order of strength of acids?
NDA Paper 2 2012

(A)

`H_2SO_4 > H_3PO_3 > CH_3COOH`

(B)

`H_3PO_3 > H_2SO_4 > CH_3COOH`

(C)

`CH_3COOH > H_3PO_3 > H_2SO_4`

(D)

`CH_3COOH > H_2SO_4 > H_3PO_3`

Solution:

Sulphuric acid is a strong acid because it completely
ionised in water to produce a large amount of hydrogen ions.
Acetic acid `(CH_3COOH)` is a weak acid because it ionise only
partially. So the correct sequence is

`H_2SO_4 > H_3PO_3 > CH_3COOH`

Correct Answer is `=>` (A) `H_2SO_4 > H_3PO_3 > CH_3COOH`

Q 2317456389

Which one among the following is a double salt?
NDA Paper 2 2012

(A)

`K_4 [Fe(CN)_6 ]`

(B)

`K_2SO_ 4. Al_2(SO_4)_3 . 24H_2O`

(C)

`CuSO_4 . 5H_2O`

(D)

`NaCl `

Solution:

Double salts are salts containing more than one cation or anion. They form when more than one salt is dissolved in a liquid and when together they crystallise in a regular lattice structure. A well-known double salt is alum containing two cations (potassium and aluminium) and a sulphate anion. Other examples are potassiurn sodium tartrate and bromlite.

Correct Answer is `=>` (B) `K_2SO_ 4. Al_2(SO_4)_3 . 24H_2O`

Q 2377067886

Bases turn red litmus blue and acids turn blue litmus red. A student tested a liquid with a red litmus paper and it stayed red with no change. This shows that the liquid.
NDA Paper 2 2011

(A)

must be pure water

(B)

must be an acid

(C)

is not a base

(D)

is neither a base nor an acid

Solution:

Bases turn red litmus blue and acids turn blue litmus red. Since, the colour of red litmus paper stayed red with no change hence the liquid is not a base. It may be be an acid or neutral.

Correct Answer is `=>` (C) is not a base

Q 2317280189

Solutions in test tubes containing `H_2O` and aqueous NaOH can be differentiated with the help of
NDA Paper 2 2011

(A)

red litmus

(B)

blue litmus

(C)

`Na_2CO_3`

(D)

`HCl` (aqueous)

Solution:

`H_2O` is neutral while aqueous NaOH is basic. Thus, `H_2O` has no effect on red litmus while aqueous NaOH turns it blue and therefore, `H_2O` and aqueous NaOH can be differentiated with the help of red litmus.

Correct Answer is `=>` (A) red litmus

Q 2347180983

Neutral water with pH about 7 becomes slightly acidic when aerated. This is because
NDA Paper 2 2010

(A)

oxygen from air is dissolved in the water which makes the water acidic

(B)

dirt, whd1 get contaminated with the water during aeration makes the water acidic

(C)

ultraviolet radiation dissociates water molecules and makes water acidic

(D)

carbon dioxide from air is dissolved

Solution:

During aeration carbon dioxide present in air dissolves in neutral water having `pH =7` and thus, the water becomes slightly acidic due to the formation of weak carbonic acid `(H_ 2CO_3 )`. `H_2O+CO_2-> H_2CO_3`

Correct Answer is `=>` (D) carbon dioxide from air is dissolved

Q 2378312206

Which one among the following is not a property of salt?
NDA Paper 2 2010

(A)

Salts have ordered packing arrangements called lattices

(B)

Salts have low melting points but high boiling points

(C)

Salts are brittle

(D)

Salts conduct electricity when dissolved in water or even in the molten state

Solution:

Salts are ionic compounds in which the constituent ions have a fixed position i.e., arranged in a definite geometric pattern. They are brittle (i.e., can be broken into pieces). They can conduct electricity in aqueous solution or in the molten state due to the presence of free ions. Being ionic, they have high melting and boiling points because there is a strong force of attraction between the oppositely charged ions so a lot of heat energy is required to break this force of attraction and to melt or boil the ionic compound.

Correct Answer is `=>` (B) Salts have low melting points but high boiling points

Q 2318312209

Which among the following statements with regard to `pH` scale is/are correct?
1. It is a logarithmic scale.
2. The scale is limited to `0-14` because the ionic product of water is about `10 ^(-14)`
.3. The lower the value of pH, the greater is the acidity of the solution.
Select the correct answer using the codes given below
NDA Paper 2 2010

(A)

1 and 2

(B)

1, 2 and 3

(C)

1 and 3

(D)

Only 2

Solution:

pH of a solution is the negative logarithm of its `H ^+` ion concentration.

`pH=-log[H^+]`
The pH range is taken to `0` to `14` and the acidity of the solution increases with decrease in the value of pH.

Correct Answer is `=>` (B) 1, 2 and 3

Q 2388012807

Vinegar is produced from
NDA Paper 2 2010

(A)

ethanoic acid

(B)

valerie acid

(C)

methanoic acid

(D)

butanoic acid

Solution:

Vinegar is dilute solution of ethanoic acid (7 to 8%), thus ethanoic acid is a source of vinegar. It is used as an appetiser for dressing food dishes.

Correct Answer is `=>` (A) ethanoic acid

Q 2337423382

Acid turns blue litmus red and base turns red litmus blue. A student tested a liquid with a red litmus paper which remained red with no change. This shows that the liquid
NDA Paper 2 2009

(A)

is not a base

(B)

is not an acid

(C)

is neither an acid nor a base

(D)

must be pure water

Solution:

Acid turns blue litmus red and base turns red litmus blue, since the colour of red litmus paper remained red with no change, hence the given liquid is not a base.

Correct Answer is `=>` (A) is not a base

Q 2367423385

Arrange the following bases in increasing order of their basic strength
l. sodium hydroxide
2. magnesium hydroxide
3. aluminium hydroxide
4. ammonium hydroxide
NDA Paper 2 2009

(A)

4, 2, 1, 3

(B)

4, 1, 2, 3

(C)

4, 3, 2, 1

(D)

1, 2, 3, 4

Solution:

On moving lefl to right within a period, the ionisation
enthalpies of the elements usually increase and hence,
hydroxides show a gradual variation from strongly basic to
strongly acidic character. Therefore, the basic strength of `NaOH,
Mg(OH)_2, Al(OH)_3` and `NH_4OH` in increasing ordler is as

`NH_4OH < AI(OH)_3 < Mg(OH)_2 < NaOH`

Correct Answer is `=>` (C) 4, 3, 2, 1

Q 2337534482

The concentration of hydrochloric acid in a given solution is `10^(-8)` M. What is the value of pH for this solution?
NDA Paper 2 2009

(A)

(B)

> 7 but not 14

(C)

< 7

(D)

Solution:

`10^(-8)` M HCl`= 10^(-8)` M+ `[H^(+)]_(H_2O)`

Total `[H^(+)] = 10^(-7) + 10^(-8)` `(·: [H^(+)]_(H_2O) =10^(-7) M)`

`= 10^(-7) (1 + 0.1)`

`=10^(-7) (1.1)`

Hence, `pH=- log (1.1 xx 10^(-7)`

`=7-0.0414=6.96`

Correct Answer is `=>` (C) < 7

Q 2357634584

When applied to the affected area, which one of the following will relieve the pain due to ant-bite or bee-sting?
NDA Paper 2 2009

(A)

Lemon juice

(B)

Vinegar

(C)

Baking soda

(D)

Caustic soda

Solution:

Ant-bite or bee-sting contains formic acid. When an ant or bee-bite, it releases formic acid, a weak acid, which ism neutralist by a weak base, sodium bicarbonate (baking soda). Therefore, when baking soda is applied to the affected area, it will relieve the pain clue to ant-bite or bee sting.

Correct Answer is `=>` (C) Baking soda

Q 2357134984

Vinegar is the trade name of
NDA Paper 2 2009

(A)

acetic acid

(B)

chloroform

(C)

carbon tetrachloride

(D)

ethyl alcohol

Solution:

`7` to `8%` dilute solution of acetic acid is called vinegar. It
is wiclely used as preservative in pickles.

Correct Answer is `=>` (A) acetic acid

Q 2317556489

Consider the following The concentration of hydrogen ions in an aqueous solution is expressed by its
1. `pH`
2. `pOH`
3. `p K_a`
4. `pK_k`
Which of the Statements given above is/are correct?
NDA Paper 2 2008

(A)

1 and 2

(B)

1 and 3

(C)

1, 2 and 3

(D)

2, 3 and 4

Solution:

`pH= -log [H^+]`

and `pK_a =-log K_alpha`

`K_a = [H^+]_·alpha`

or `K_a =-log [H^+]alpha`

Hence, the concentration of Hydrogen ions in an aqueous
solution is expressed by its `pH ` and `pK_a` .

Correct Answer is `=>` (B) 1 and 3

Q 2387878787

Which one of the following salts when dissolved in water makes the solution basic?
NDA Paper 2 2007

(A)

Sodium chloride

(B)

Copper sulphate

(C)

Ferric chloride

(D)

Sodium acetate

Solution:

Sodium acetate (`CH_3CO ONa`) is a salt of strong base
and weak acid, hence it gives basic solution on hydrolysis.

`CH_3C O ONa+H_2O ⇋ underset(text(weak acid))(CH_3CO OH)+underset(text(strong base))(NaOH)`

Correct Answer is `=>` (D) Sodium acetate