NCERT MCQ Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

Baking soda (sodium bicarbonate) neutralizes excess hydrochloric acid in the stomach, providing relief from indigestion and heartburn. It acts as a mild antacid and is commonly used in medicinal antacid formulations.

A base changes the color of red litmus to blue, indicating the presence of hydroxide ions. This is a standard test to identify basic substances in laboratories and educational demonstrations.

Lemon juice is acidic due to citric acid and has a pH below 7. Acids donate protons in solution and have a sour taste, commonly found in many fruits and food items.

Zinc reacts with dilute hydrochloric acid to produce hydrogen gas and zinc chloride. The reaction is used to demonstrate metal-acid interactions and gas collection techniques in school laboratories.

In a neutralisation reaction, hydrogen ions from the acid and hydroxide ions from the base react to form water and salt. It’s an important reaction in chemistry and biology for maintaining pH balance.

Lime water (Ca(OH)₂) reacts with carbon dioxide to form calcium carbonate (CaCO₃), a white precipitate. This reaction is often used as a simple laboratory test to detect the presence of CO₂ gas.

Turmeric is a natural indicator that turns reddish-brown in basic solutions and remains yellow in acidic or neutral solutions. It is used to detect household acid-base changes.

Sodium bicarbonate reacts with acid to release carbon dioxide, which displaces oxygen and extinguishes fire. This makes it an effective component in soda-acid type fire extinguishers used for Class B and C fires.

Vinegar is a dilute solution of acetic acid, which gives it a sour taste and antimicrobial properties. Acetic acid is also used in food preservation and as a laboratory reagent.

Neutral water has a pH of 7 at 25°C, indicating equal concentrations of hydrogen and hydroxide ions.
The pH scale ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

Formic acid, also called methanoic acid, is responsible for the pain and irritation caused by ant and bee stings. Applying a mild base like baking soda helps neutralize its effect.

Lemon juice is acidic and turns blue litmus red. This color change is a common test to detect the presence of an acid, widely demonstrated in classrooms using fruit extracts.

Plaster of Paris (POP) is calcium sulfate hemihydrate, which hardens when mixed with water. It is widely used for making casts, moulds and in construction for decorative elements.

Universal indicators are mixtures of pH indicators that show a green color at pH 7, indicating a neutral solution such as pure water. Different pH values give distinct color changes.

This notation indicates that the salt contains ten molecules of water per formula unit. These water molecules are part of the crystal structure, making it a hydrated salt (washing soda).

Sodium carbonate (washing soda) is a key ingredient in glass production and soap manufacturing. It reduces the melting point of silica and removes hardness-causing ions in water during cleaning.

Stomach acid contains hydrochloric acid, which has a low pH of 2–3. This acidic environment aids in food digestion and helps kill harmful microbes present in ingested food.

Carbon dioxide reacts with lime water to form calcium carbonate, which is insoluble in water and appears as a white precipitate. This reaction is used to detect CO₂ gas.

Heating baking powder releases carbon dioxide gas, which causes baked goods to rise. The reaction involves sodium bicarbonate and a mild acid reacting upon heating to produce the gas.

Sodium bicarbonate is considered an acidic salt because it can act as a weak acid in aqueous solution. It’s amphoteric and reacts with both acids and bases under appropriate conditions.