Question 1

Which of the following substances has a pH value closest to 7 at room temperature?

Accepted Answer

Correct Option: B Pure water is a neutral substance and has a pH value of exactly 7 at 25°C. The pH scale ranges from 0 to 14, where values less than 7 indicate acidic nature, values greater than 7 indicate basic (alkaline) nature, and exactly 7 represents neutrality. Lemon juice is acidic (pH 2), s

Question 2

When dilute hydrochloric acid reacts with sodium carbonate, which gas is evolved?

Accepted Answer

Correct Option: C When an acid reacts with a metal carbonate or metal bicarbonate, it produces salt, water, and carbon dioxide gas. The chemical equation for this reaction is: Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)↑. The evolved carbon dioxide gas can be confirmed by passing it through l

Question 3

Which of the following is a characteristic of acids?

Accepted Answer

Answer: Acids are known for their sour taste. They also have a pH less than 7 and release H⁺ ions in aqueous solutions. They neutralize bases and turn litmus paper red. Explanation: The sour taste is a classic sensory property of acids, distinguishing them from bases and salts.

Question 4

Which base is commonly used in household cleaning?

Accepted Answer

Answer: Sodium hydroxide (NaOH) is widely used in household cleaning products such as drain cleaners and soaps. It effectively removes grease and dirt by saponifying fats and dissolving organic matter. Explanation: NaOH is a strong base that reacts with oils and proteins, making it ideal for cleanin

Question 5

When an acid reacts with a metal carbonate, what is produced?

Accepted Answer

Answer: Carbon dioxide gas (CO₂) is released. The reaction also produces a salt and water. Explanation: The acid donates H⁺ ions which combine with CO₃²⁻ to form CO₂ gas, while the metal cation forms a salt with the anion of the acid.

Acids, Bases and Salts — CBSE Class 10 Science Important Questions & Revision Notes