Chemistry in Class 10 : Practice MCQ Questions & Answers with Explanations

Hydrochloric acid is a strong acid. It dissociates completely in water, releasing a high concentration of hydrogen ions, making it much stronger than weak acids like acetic or citric acid.

Sodium hydroxide is commonly known as caustic soda. It is a strong alkaline substance used in many industrial processes, such as soap making and water treatment.

When an acid reacts with a metal, it typically forms a salt and releases hydrogen gas. For example, hydrochloric acid reacts with zinc to form zinc chloride and hydrogen gas.

Burning a candle is a chemical reaction. The wax reacts with oxygen to produce carbon dioxide, water, and energy, changing the chemical composition of the substances involved.

Helium is a noble gas, which is chemically inert and doesn't readily form compounds with other elements due to its stable electron configuration.

A chemical reaction involves the transformation of one or more substances into new substances with different properties. It is a chemical change, not merely a physical one.