NCERT Question 6 - Chapter 5 Class 7 - Acid, Bases and Salt

Mark ‘T’ if the statement is true and ‘F’ if it is false:

1. Nitric acid turn red litmus blue. (T/F)
2. Sodium hydroxide turns blue litmus red. (T/F)
3. Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)
4. Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)
5. Tooth decay is caused by the presence of a base. (T/F)

Answer:

(a)

• Nitric acid is acidic in nature.
• Acids turn blue litmus red , and produce no colour change in red litmus .
• Hence it does not change the colour of red litmus.

Therefore, the statement is false.

(b) 

• Sodium Hydroxide is basic in nature 
• Bases turn red litmus blue , and produce no colour change in blue litmus .
• Hence it does not change the colour of blue litmus.

Therefore, the statement is false.

(c)

• Sodium hydroxide is a base and hydrochloric acid is an acid.
• They neutralise each other and form salt and water.

Therefore, the statement is true.

(d) 

• Indicator is a substance which is used to indicate the nature of a chemical.
• It is used this way because it shows different colours in acidic and basic solutions .

Therefore, the statement is true.

(e) False

• Tooth decay is caused due to the presence of acids .
• Our body releases acids to digest food in our mouth, which if left over, causes damage to the tooth and tooth decay .

Therefore, the statement is false.