State any two uses of sodium, magnesium, copper, zinc, aluminium, iron, gold, and silver. Distinguish between hard and soft water and state 3 advantages of each.

Here are the answers to your questions. 4. State any two uses of the following metals. i. Sodium: • Used in street lamps (sodium vapor lamps). • Used as a coolant in nuclear reactors. ii. Magnesium: • Used in flares and fireworks. • Used in lightweight alloys for aircraft. iii. Copper: • Used in electrical wiring. • Used in plumbing pipes. iv. Zinc: • Used for galvanizing steel to prevent rust. • Used in batteries (e.g., dry cells). v. Aluminium: • Used in aircraft construction. • Used for making beverage cans. vi. Iron: • Used in construction (e.g., steel beams). • Used for making tools and machinery. vii. Gold: • Used in jewelry. • Used in dentistry and electronics. viii. Silver: • Used in jewelry and coinage. • Used in photography and electrical contacts. 5. (a) Distinguish between hard and soft water. Hard water* contains dissolved mineral ions, primarily calcium (Ca^2+) and magnesium (Mg^2+) ions, and does not readily form lather with soap. Soft water* contains very few or no dissolved mineral ions and readily forms lather with soap. 5. (b) State 3 advantages of soft water and 3 advantages of hard water. Advantages of soft water: • Forms lather easily with soap, reducing soap consumption. • Does not form scale in pipes and boilers, preventing blockages. • Better for washing clothes and dishes as it cleans more effectively. Advantages of hard water: • Contains essential minerals like calcium and magnesium, beneficial for human health. • Has a pleasant taste due to dissolved minerals. • Suitable for brewing beer and tanning leather. 5. (c) State 2 disadvantages of soft water and 2 disadvantages of hard water. Disadvantages of soft water: • Lacks beneficial minerals like calcium and magnesium. • Can be corrosive to lead pipes, dissolving lead into the water. Disadvantages of hard water: • Wastes soap as it does not readily form lather. • Forms scale (limescale) in kettles, pipes, and boilers, reducing efficiency. 5. (d) Explain any 3 ways of removing water hardness. 1. Boiling: This method removes temporary hardness. Boiling causes the soluble bicarbonates of calcium and magnesium to decompose into insoluble carbonates, which then precipitate out. Ca(HCO_3)_2(aq) heat CaCO_3(s) + H_2O(l) + CO_2(g) 2. Adding washing soda (sodium carbonate): Washing soda reacts with calcium and magnesium ions to form insoluble carbonates, which precipitate out of the water. This method removes both temporary and permanent hardness. Ca^2+(aq) + Na_2CO_3(aq) CaCO_3(s) + 2Na^+(aq) 3. Ion exchange method: Hard water is passed through a column containing ion-exchange resins. These resins exchange their sodium ions for the calcium and magnesium ions present in the hard water, effectively softening it. 2RNa(s) + Ca^2+(aq) R_2Ca(s) + 2Na^+(aq) That's 2 down. 3 left today — send the next one.