Strength of Acid and Bases

Write a short notes on p^H scale (Draw a diagram)

Ans.  i) p^H scale helps in measing the hydrogen ion (H⁺) concentration in a solution.

ii) The p^H scale ranges from 0 to 14.

iii) p^H value 7 represents a neutral substance i.e. neither acidic nor basic.

iv) An acidic substance has a p^H value between 0 to 7 & a basic substance with p^H value 7 to 14.

v) Lower the p^H of an acid, greater is the concentration of H⁺ ions, greater the p^H of a base, greater is the concentration of OH^- ions.

What are strong acids ? Give two examples.

Ans. When acids in aqueous solution give more number of H⁺ ions they are termed as strong acids.

ii) Sulphuric acid H₂so₄, hydrochloric acid, HCl, nitric acids HNO₃ are strong acids.

What are weak acids? Give two examples.

Ans. i) When acids in aqueous solution give less numbers of H⁺ ions, they are termed as weak acids.

ii) Ammonium hydroxide (NH₄OH), Magnesium hydroxide (Mg(OH)₂), (OH)₂ copper hydroxide Cu(OH)₂are weak bases.

How does a tooth paste help in preventing tooth decay ?

Ans. i) Tooth decay is caused by acids produced by certain bacteria that are found in our mouth. These acids corrode the tooth enamel.

ii) Toothpaste contains alkaline substances & fluoride which neutralizes the acids in mouth. This prevents corrosion of the tooth enamel.

Explain the effect of acid rain on aquatic life in a river.

Ans.  i) Pure water is neutral having p^H.7

ii) Rain water reacts with carbon dioxide, Oxides of nitrogen & sulphur dioxide in the air & becomes acidic. Acid rain has p^H less than 7.

iii) When acid rainwater flows in rivers, it lowers the p^H of river water to less than 7.

iv) When plants absorb acidic water, it adversely affects their growth, flower, fruits & even their leaves.

v) Acidic water is very harmful to aquatic life e.g. fish, frogs, aquatic plants, etc.

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