Question 1: Define a metal hydroxide and describe how it is generally formed.

Answer: A metal hydroxide is a compound formed when a metal reacts with water or oxygen, resulting in a substance with the formula MOH or M(OH)₂, where M is a metal. It is typically formed through the reaction of a metal with water or by the precipitation of metal ions with hydroxide ions.

Question 2: Explain the typical physical state and solubility of most metal hydroxides in water.

Answer: Most metal hydroxides are solid at room temperature and vary in solubility; some, like sodium hydroxide, are highly soluble, while others, like aluminum hydroxide, are sparingly soluble or insoluble.

Question 1: A student reacts solutions of metal salts with sodium hydroxide and notes the formation of precipitates. The precipitates vary in color: blue, green, and brown. Match each color to a possible metal hydroxide based on typical properties.

Answer: Blue: Copper(II) hydroxide, Green: Iron(II) hydroxide, Brown: Iron(III) hydroxide.

Question 2: Given the following data, determine which metal hydroxide is most soluble in water: Sodium hydroxide (NaOH), Aluminum hydroxide (Al(OH)₃), or Calcium hydroxide (Ca(OH)₂). Data: NaOH - complete dissociation, Al(OH)₃ - sparingly soluble, Ca(OH)₂ - moderately soluble.

Answer: Sodium hydroxide (NaOH) is the most soluble in water among the three.

Question 1: Calculate the mass of aluminum hydroxide (Al(OH)₃) required to prepare 250 mL of a 0.5 mol/L solution. (Molar mass of Al(OH)₃ = 78 g/mol)

Answer: Mass = molarity × volume × molar mass = 0.5 mol/L × 0.25 L × 78 g/mol = 9.75 grams

Question 2: If 10 grams of calcium hydroxide (Ca(OH)₂) is dissolved in water, what is the concentration of the solution in mol/L? Molar mass of Ca(OH)₂ = 74 g/mol.

Answer: Moles of Ca(OH)₂ = 10 g / 74 g/mol ≈ 0.135 mol; concentration = 0.135 mol / 1 L ≈ 0.135 mol/L

Question 1: Describe the safety precautions students should follow when handling metal hydroxides in the laboratory.

Answer: Students should wear safety goggles, gloves, and lab coats; avoid inhaling dust or fumes; handle chemicals carefully; and dispose of waste properly.

Question 2: Design a simple experiment to test the solubility of different metal hydroxides in water. Include variables to control and measure.

Answer: Students can weigh equal amounts of different metal hydroxides (e.g., NaOH, Ca(OH)₂, Al(OH)₃), dissolve them in a fixed volume of water, and observe the amount that dissolves completely or forms precipitates. Control variables include temperature, volume of water, and initial mass of hydroxide. Measure the dissolved amount by filtration and weighing the residue.

Question 1: Describe one industrial use of sodium hydroxide, a metal hydroxide, and its importance.

Answer: Sodium hydroxide is used in soap making, paper production, and pH regulation in industries, which is essential for manufacturing and chemical processes.

Question 2: Explain how metal hydroxides are involved in water treatment processes.

Answer: Metal hydroxides like aluminum hydroxide are used to remove impurities and neutralize acidity in water treatment, making water safe for consumption.