Acids & Bases — Set 6

Correct Answer: D. Oxalic acid

Tomatoes contain oxalic acid along with smaller amounts of citric and malic acids. Oxalic acid is also found in spinach and can contribute to the formation of kidney stones. It is often used in the lab to standardize potassium permanganate solutions.

Correct Answer: B. Aqua Regia

Aqua Regia, or 'Royal Water', is a powerful mixture that can dissolve noble metals like gold. It consists of three parts concentrated hydrochloric acid and one part concentrated nitric acid. This mixture is highly unstable and must be prepared fresh.

Correct Answer: B. Lime water

Lime water is a solution of calcium hydroxide that reacts with CO2 to form insoluble calcium carbonate. The formation of this white precipitate makes the solution look cloudy or milky. This is the standard laboratory test for identifying carbon dioxide gas.

Correct Answer: C. Hydrochloric acid

Hydrochloric acid was traditionally called spirit of salt because it was produced from common salt. It is a major mineral acid with a wide range of uses in metal processing. The human stomach naturally produces it to aid in food digestion.

Correct Answer: B. Bromothymol blue

Bromothymol blue is a chemical indicator used for measuring substances near neutral pH. it is yellow in acidic solutions, green in neutral, and blue in basic ones. It is commonly used in biology experiments to detect respiratory CO2.

Correct Answer: D. Aluminum hydroxide

Aluminum hydroxide is a common active ingredient in antacid liquids and tablets. It works by reacting with excess hydrochloric acid in the stomach to form salt and water. It is often combined with magnesium hydroxide to balance digestive side effects.

Correct Answer: B. Less than 5.6

The correct answer is 'Less than 5.6'. Rain is considered 'acid rain' when its pH falls below 5.6 due to atmospheric pollutants. Normal rainwater is slightly acidic (pH 5.6) because of dissolved carbon dioxide. Acid rain can damage buildings, forests, and aquatic ecosystems significantly.

Correct Answer: A. Hydrochloric acid

Hydrochloric acid is used in the pickling process to remove rust or scale from iron or steel surfaces. This cleaning is necessary before the metal is coated or galvanized. It ensures a strong bond between the base metal and the protective layer.

Correct Answer: A. Calcium hydroxide

Calcium hydroxide (dry slaked lime) reacts with chlorine gas to produce bleaching powder. The chemical name for bleaching powder is calcium hypochlorite. It is widely used as a disinfectant and for whitening fabrics.

Correct Answer: A. Butyric acid

Butyric acid is responsible for the unpleasant smell and taste associated with rancid butter. It is a carboxylic acid that is released when fats in the butter undergo hydrolysis. It is also found in animal fats and plant oils.