Acids Bases and Salts Class 10 Important Questions and Answers Science Chapter 2

 Acids Bases and Salts Class 10 Important Questions and Answers Science Chapter 2

Very Short Answer Questions

Question 1.

Give the names and formulae of two

(i) strong monobasic acids

(ii) two weak dibasic acids.

Answer:

(i) hydrochloric acid (HCl), nitric acid (HNO3)

(ii) carbonic acid (H2CO3), oxalic acid (C2H2O4).

More Resources



 

Previous Year Question Papers for CBSE Class 10 Science

NCERT Solutions for Class 10 Science

NCERT Exemplar Solutions for Class 10 Science

Value Based Questions in Science for Class 10

HOTS Questions for Class 10 Science

Question 2.

How will you show that acetic acid is a monobasic acid ?

Answer:

When acetic acid is reacted with sodium hydroxide solution, only one H atom of the acid gets replaced and the product is sodium acetate and water. This shows that acetic acid is a monobasic acid.



Question 3.

Why alkalies like sodium hydroxide and potassium hydroxide should not be left exposed to air ?

Answer:

Because they are hygroscopic in nature and absorb moisture from atmosphere in which they ultimately dissolve.



 

Question 4.

The pH of an aqueous solution decreases from 3 to 2. What will happen to the nature of the solution ?

Answer:

The acidic character of the solution will further increase.

Question 5.

What happens to the crystals of washing soda when exposed to air ?

Answer:

They undergo efflorescence. As a result, washing soda (Na2CO3.10H2O) changes to washing powder (Na2CO3.H2O).

Question 6.

State whether an aqueous solution of washing soda is acidic or alkaline.

Answer:

An aqueous solution of washing soda is alkaline (turns red litmus blue). On dissolving in water, it forms NaOH (strong base) and carbonic acid (weak acid).



Therefore, resulting solution is alkaline or basic in nature.



 

Question 7.

What is the chemical name and chemical formula of baking soda ?

Answer:

The chemical name of baking soda is sodium hydrogen carbonate or sodium bicarbonate. Its chemical formula is NaHCO3.

Question 8.

When a few drops of phenolphthalein indicator were added to the solution of some compound A’, the solution became pink. What does it indicate ?

Answer:

This shows that the solution of compound A’ is of basic nature since phenolphthalein becomes pink in basic medium.

Question 9.

Which is a stronger acid ? A solution with pH 5 and a solution with pH 2 ?

Answer:

A solution with pH 2 is a stronger acid. In general, lesser the pH, more will be the acidic nature of the solution.

Question 10.

What is the nature of NaHCO3 salt ?

Answer:

It is an acidic salt since it has still one replaceable hydrogen atom present.

Question 11.

Give two examples of the salts belonging to the chloride family.

Answer:

Sodium chloride (NaCl) and potassium chloride (KCl).



 

Question 12.

What will be the colour acquired by a basic solution if a few drops of indicator methyl orange are added to it ?

Answer:

The solution will acquire a yellow colour.

Question 13.

Name the gas evolved when dilute HCl reacts with sodium hydrogen carbonate. How is it recognised ?

Answer:

The gas evolved is carbon dioxide (CO2). When the gas is bubbled through lime water, it becomes milky.

Question 14.

Arrange the following in increasing order of their pH values :

NaOH solution, blood, lemon juice

Answer:

Increasing order of pH values is : lemon juice < blood < NaOH solution

Question 15.

How does the pH change when the solution of base is diluted with water ?

Answer:

Upon diluting a solution of base with water, the number of OH’ ions in solution per unit volume decrease. The basic strength of the base decreases and pH of solution decreases.

Question 16.

Which one of these has a higher concentration of H+ ions ?

Answer:

IM HCl or IM CH3COOH.

Although both the acid solutions have the same molar concentration (lM) in aqueous solution, but HCl will release more H+ ions as compared to CH3COOH since it is a stronger acid.

Question 17.

Which bases are called alkalies ? Give an example of alkalies ?

Answer:

Water soluble bases are called alkalies. Sodium hydroxide (NaOH) is an example of alkalies.

Question 18.

Name the natural source of each of the following :

(a) Citric acid

(b) Oxalic acid

(c) Lactic acid

(d) Tartaric acid. (CBSE 2014)

Answer:

(a) Citrus fruits like lemons and oranges

(b) Tomatoes

(c) Milk

(d) Tamarind.

Question 19.

Write the name and chemical formula of the main product formed by heating baking soda.

Answer:

Baking soda is chemically sodium hydrogen carbonate (NaHCO3). Upon heating, it forms sodium carbonate (Na2CO3) as the main product.



Question 20.

Write the names and chemical formulae of the products formed by heating gypsum at 373 K.

Answer:

Gypsum upon heating to 373 K forms Plaster of Paris and water



Question 21.

A student tested the pH of distilled water and found that the colour of pH paper changed to light green.

He found the pH again after dissolving a pinch of common salt in it. What will be colour of pH paper ?

Answer:

Distilled water is neutral with pH close to 7. An aqueous solution of common salt is also neutral. This means that there will be no change in the pH. The colour of pH paper will remain the same i.e., light green.

Question 22.

The pH of rain water collected from two cities A and B was found to be 6 and 5 respectively. The water of which city is more acidic ?

Answer:

Rain water of city B with pH 5 is more acidic.

Question 23.

Why does an aqueous solution of alcohol fail to conduct electric current ?

Answer:

An aqueous solution of alcohol fails to conduct electric current since it does not release H+ ions in solution.

Question 24.

Name the chemical substance which constitutes bees sting.

Answer:

It is methanoic acid or formic acid (HCOOH).

Question 25.

Which substance constitutes the enamel coating of our teeth ?

Answer:

Calcium phosphate Ca3(PO4)2 constitutes the enamel coating of our teeth.

Question 26.

What happens when a base reacts with a non-metallic oxide. What would you infer about the nature of the non-metallic oxide ?

Answer:

A base reacts with a non-metal oxide to form salt and water. The non-metal oxide is, therefore, an acidic oxide. For example.

2 NaOH (aq) CO2 (g) ———> Na2CO3 (aq) + H2O (aq) .

Question 27.

Name the acids and bases from which the following salts may be obtained.

(i) Potassium sulphate

(ii) Calcium chloride

Answer:

(i) Potassium hydroxide (KOH), Sulphuric acid (H2SO4)

(ii) Calcium hydroxide Ca(OH)2, Plydrochioric acid (HCl)

Question 28.

What will be the pH of the following salt solutions.

(i) Salt made from strong acid and strong base.

(ii) Salt made from strong acid and weak base.

Answer:

(i) The solution will be neutral with pH close to 7 (e.g. NaCl).

(ii) The solution will be acidic with pH less than 7 (e.g. NH4Cl).

Question 29.

Give examples of two substances having water of crystallisation. Write their formulae also.

Answer:

Blue vitriol or hydrated copper sulphate : CuSO4. 5H2O.

Green vitriol or hydrated ferrous sulphate : FeSO4. 7H2O.

Question 30.

What are the pH values of distilled water and common salt solution ?

Answer:

Both are neutral and have pH close to 7.

Question 31.

Which one is a stronger acid, with = 5 or with pH = 2 ?

Answer:

The acid with pH = 2 is a stronger acid.

Question 32.

The pW of three solutions A, B and C are 4, 9 and 6 respectively. Arrange them in increasing order of acidic strength.

Answer:

The increasing order of acidic strength is : B < C < A.