The question asks why Milk of Magnesia is used as an antacid. Antacids are substances that neutralize stomach acid (hydrochloric acid, HCl) to relieve symptoms like heartburn or indigestion. We need to identify the option that correctly describes this chemical action and its properties.
D) It is a weak base that neutralises excess hydrochloric acid in the stomach without being harmful to the body
This option accurately describes the mechanism of action of Milk of Magnesia. Magnesium hydroxide is a weak base, which means it does not fully dissociate in water and thus neutralizes acid gently. This property makes it safe for consumption as an antacid, as it effectively reduces stomach acidity without causing damage to the stomach lining.
This question tests basic knowledge of acid-base indicators, specifically the behavior of litmus paper. Litmus paper is a common indicator used to determine whether a solution is acidic or basic.
A) Turns it blue — Bases are known to turn red litmus paper blue. This is a fundamental concept in chemistry regarding acid-base indicators.
An amphoteric oxide is an oxide that can react with both acids and bases to form salt and water. We need to identify which of the given options exhibits this dual nature.
Correct Option: C) Zinc oxide (ZnO) is an amphoteric oxide because it reacts with both acids and bases.
The question asks to identify the natural source from which litmus solution, a common acid-base indicator, is extracted. This requires knowledge of common natural indicators and their origins.
B) Lichens (a symbiotic organism of algae and fungi) — Litmus is a natural dye extracted from various species of lichens. It is one of the oldest and most widely used pH indicators.
This question tests knowledge of common acid-base indicators, specifically phenolphthalein. Indicators are substances that change color depending on the pH of the solution they are in. Phenolphthalein is widely used in titrations and general chemistry to identify acidic, neutral, and basic conditions.
B) Colourless, colourless, pink/magenta. This option correctly describes the color of phenolphthalein in acidic, neutral, and basic solutions, respectively.
The question asks about the color change of methyl orange indicator in an acidic solution. To answer this, one needs to recall the characteristic pH range and corresponding color changes for methyl orange.
A) Red — Methyl orange is a pH indicator that shows a red color in acidic solutions (pH less than 3.1). It transitions to orange in the pH range of 3.1-4.4 and becomes yellow in basic solutions (pH greater than 4.4).