Question 1: Metal hydroxides are compounds formed when metal ions react with hydroxide ions (OH⁻). They often appear as insoluble or sparingly soluble solids and have characteristic tests to identify the metal involved.

Answer: Metal hydroxides are compounds formed from metal ions and hydroxide ions, typically insoluble solids used in various chemical tests.

Question 1: Explain how metal hydroxides are formed in aqueous solutions.

Answer: Metal hydroxides form when metal cations react with hydroxide ions in water, often resulting from the dissociation of metal salts or base reactions.

Question 2: Describe a typical physical property of metal hydroxides that helps in their identification.

Answer: Many metal hydroxides are insoluble in water and form precipitates.

Question 1: Calculate the concentration (in mol/dm³) of hydroxide ions in a solution prepared by dissolving 0.5 mol of aluminium hydroxide, Al(OH)₃, in 1 dm³ of water. (Given: Al(OH)₃ dissociates partially, but assume full dissociation for simplicity).

Answer: 0.5 mol/dm³

Question 1: Design a simple test to identify a metal hydroxide precipitate in a solution. Mention the safety precautions you would take.

Answer: Add dilute hydrochloric acid to the suspected metal hydroxide. Observe for the evolution of a gas (such as hydrogen). Safety precautions include wearing safety goggles, gloves, and working in a well-ventilated area to avoid inhaling any fumes or splashes.

Question 1: A solution containing a metal hydroxide produces a white precipitate when reacted with excess sodium hydroxide. When tested with dilute acid, the precipitate dissolves, releasing a gas. What metal could this hydroxide contain? Justify your answer.

Answer: It could contain aluminium because aluminium hydroxide forms a precipitate with sodium hydroxide and dissolves in acid to release hydrogen gas.

Question 1: Describe the process of testing for magnesium hydroxide in a laboratory. Include the observation you would expect and the safety considerations.

Answer: To test for magnesium hydroxide, add dilute hydrochloric acid to the sample. If magnesium hydroxide is present, it will react to produce magnesium chloride and water, and hydrogen gas may be evolved. Observe for effervescence. Safety measures include wearing goggles and gloves, working in a fume hood if necessary, and handling acids carefully.

Question 1: Explain how aluminium hydroxide is used in medicine and why it is suitable for this purpose.

Answer: Aluminium hydroxide is used as an antacid to neutralise stomach acid because it reacts with hydrochloric acid to reduce acidity, providing relief from indigestion.