Revision Series | Science | Acids & Bases | 4

Answer- C

• A pH at exactly 7 is neutral.
• The higher the [H+], the lower the pH.
• The pH scale shows that substances with a pH greater than 7 are basic and a pH less than 7 are acidic.

Strength of Acid or Base Solutions

Strength of an acid or base can be determined using a pH scale.

It is a scale to measure the hydrogen ion concentration in a solution.

The p stands for ‘potenz’, it is a German word that means power.

If pH is equal to 7, it means the solution is neutral.

If pH is greater than 7 means alkaline solution.

If pH is less than 7 means the solution is acidic.

• Human body works at a pH of about 7.4.
• The stomach has a pH of about 2 due to the presence of hydrochloric acid in it.

Answer- D

Sodium hydrogen carbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.

A double displacement reaction occurs when sodium carbonate is introduced into hydrochloric acid and forms sodium chloride, Water, and carbon dioxide.

Sodium Carbonate

• Sodium carbonate is referred to as washing soda.
• It is basic in nature and reacts with acids.
• It is employed in manufacturing glass and acts as a water softener.

Hydrochloric Acid

• Hydrochloric acids are strong acids and react with bases.

It is used in a wide range of Industries

Answer- C

Answer- B

Hence, Chlorine undergoes Oxidation in this reaction. Calcium oxychloride. Note: Bleaching powder is also called chlorine powder, chloride of lime or chlorinated lime. The other chemical name is Calcium hypochlorite.

Answer- A

The correct answer is colorless and pink.

Phenolphthalein remains colorless in acidic solution but turns pink in the basic solution.

Answer- A

Citric acid and tartaric acid are two edible acids.

These acids are responsible for the sharpness of any food’s flavor.

These acids are present to some degree in all fruits, giving them their distinctive flavor.

Citric acid, malic acid, and tartaric acid are all naturally occurring food acids.

Answer- D

• Acids turns blue litmus paper red. acids turn blue litmus to red. Litmus turns blue when it comes into contact with acids. When blue litmus paper is placed in an acidic solution, it becomes red. However, when placed in a basic or neutral substance, it will remain blue.
• Aqueous solutions of acids conduct electricity. Acid dissociates into ions in aqueous solution. The migration of movements helps in conducting electricity. Thus, aqueous solution of acid conduct electricity.
• Acids react with certain metals to form hydrogen gas.

Answer- D

As the reaction releases heat or is exothermic in nature, the temperature increases and the test tube becomes hot. Hence, when a solution of an acid is mixed with a solution of a base in a test tube, the temperature of the solution increases and salt formation takes place.

Answer- D

The pH scale starts from 0 and ends at 14, 0 indicating most acidic and 14 indicating most basic.

The pH value of 7 indicates neutrality.

Hence lower the pH, weaker the base and higher the pH, weaker the acid.

(ii) and (iv) is the correct statement about an aqueous solution of an acid and of a base.

Answer- A

• Nettle stings contain formic acid, histamine, and other chemicals.
• Formic acid is also known as methanoic acid (HCOOH).
• Nettle stings contain formic acid. When the fine hairs on the leaves and stems of nettles come into contact with the skin, they can cause a stinging or burning sensation.
• This is because the hairs contain small amounts of formic acid, which is also found in the venom of some insects, such as ants and bees.
• Formic acid is a colorless, strong-smelling liquid that occurs naturally in the bodies of many organisms, including some plants and animals.