Acid, Base and Salt : Class 10 Science Exercise

b. The taste of acid is sour.

Ans: The taste of acid is sour is because  acid contains hydrogen ions ( H+).

c. Acetic acid is a weak acid.

Ans: Acetic acid is a weak acid because it undergoes partial ionisation to give less concentration of hydrogen ions.

d. Hydrochloric acid is known as a strong acid.

Ans: Hydrochloric acid is known as a strong acid because it undergoes complete ionisation to give more concentration of hydrogen ions. 

e. Sodium bicarbonate is called an acidic salt.

Ans: Sodium bicarbonate is called an acidic salt because it contains ionizable hydrogen ions in it.

f. Water is known as an acid as well as a base.

Ans: Water is known as an acid as well as a base because water gives both hydrogen ions ( H+ ) and hydroxyl ions ( H- ) on dissociation.  It shows amphoteric behaviour. 

g. Ammonium hydroxide is called a weak alkali.

Ans: Ammonium Hydroxide is called a weak acid because it is soluble in water. 

h. H2SO4 is called the king of chemicals.

Ans: H2SO4 is called a king of chemicals because it is widely used in industries and laboratories. 

i. Acid is also called a proton donor. 

Ans: Acid is also called a proton donor because theu gives hydrogen ions or proton by dissolving in water. 

j.  Antacids relieve hyper-acidity

Ans: Antacids relieve hyper-acidity because antacids are mild bases that neutralises the effect of acid in our stomach. 

4. Answer the following questions:

a. Define acids ? What are the properties of acids.

Ans: Acids are those compounds which gives off hydrogen ions or proton when dissolved in water. 
The properties of acid are as follows:
• They are sour
• It turns blue litmus paper into red
• It can conduct electricity 
• It feels sticky

b. Write down the name and molecular formula of a compound which gives hydrogen ion and chloride ion in the solution state. In which colour is the methyl orange changed after treating it with this compound? Why? Write the name of salt when the compound is treated with lime water. Write down the chemical equation.

Ans: The name and Molecular formula of compound which gives hydrogen ions and chloride in solution state is given below:

 Hydrochloric Acid → chlorine + Hydrogen
                    2Hcl      → Cl₂ + H₂

Methyl Orange changes into Red because the Compound is acidic in nature. 
The name of salt when treated with the compon is calcium chloride.
 Ca (OH)₂+ 2HCl → Cacl₂+ H₂O

c. Define organic and Mineral acids .

Ans: The acids obtained from living organisms and Contain carbon in their molecular structure is called Organic acid.

The acids which are obtained from minerals found on the earth's crust and do not contain carbon atoms in their molecular structure are called Mineral acids.

d. What is a base ? Mention any three ways of making bases .

Ans: Metallic oxides and hydroxides which are bitter in taste and give hydroxyl ions (H+) if they dissolve in water are called bases .
The three ways of making bases are as follows:
• By the direct union of a metal with oxygen
• By the action of water or steam on some active metals
• By heating carbonates of some metals

e. What are salts ? What are the characteristics of salts ?

Ans: Salts are the compound which is formed by the partial or complete replacement of one or more hydrogen atoms of an acid by one or more metal atom or positive radicals .

The characteristics of  salts are as follows :
• Common salt is an important constituent of our diet.
• Most salts are insoluble in water but few are soluble.
• The solution of salt can conduct electricity. 

f . What is an alkali ? Name any three alkalis.

Ans: Alkalis are water soluble bases which give hydroxyl ions when dissolved in water.
The three examples of allkalis are as follows:
 • Naoh 
• KOH
• Ca ( OH )₂

g. What do you mean by neutralization reaction? Write the importance of this reaction.

Ans: The reaction in which the properties of acid and bases are destroyed or neutralize to form salt and water is known as neutralization reaction.
Some importance of neutralization reaction are as follows:
• It is used to control the PH of soil .
• It is used in the manufacturing of antacid. 
• It is used as household remedy for bee or and sting.

h. " Acids are said to be proton donors" Justify.

Ans: Acids are called to said to be proton donors because they lose proton to other atoms in chemical reaction This makes them more electro negative as they will have more number of electrons than protons .

i. Which alkali has no metal ?

Ans: Ammonium Hydroxide is an alkali which has no metal.

j. What is litmus paper ? Where is it used ? How is it used for identifying acid and base?

Ans: A litmus paper is an indicator which identifies whether the given substance is acid, base or neutral by changing its color .

It is used in Chemical Laboratory.

If the substance is acid blue litmus paper changes its color into red and if the substance is base red litmus paper changes its color in blue .

k. How normal acidic and basic salts are formed ? Explain with chemical reaction.

Ans: Normal salts are formed by the reaction of  strong acids and strong bases or weak acid and weak base.

HCl + NaoH → Nacl+ H₂O

Acidic salts are produced when strong acid and weak bases are reacted .
H₂SO4 + KOH →KHSO4 + H₂O

Basic salt are formed by the reaction of weak acid and strong base.
NaoH + H₂Co3 → Na₂Co + H₂O

l. What changes of colour would you observe when the following indicators are added to the substance given below: