Which of the following solutions is most likely to be acidic rain? Which type of substance reacts with both strong acids and strong bases? Name one substance that exhibits this property. Why does the

*a) (i) Acidic rain typically has a pH below 5.6. Among the given solutions, solution X with a pH of 2.2 is the most acidic and is likely to be acidic rain.

*a) (ii) Solution Y (pH 13.5) is strongly basic, and solution X (pH 2.2) is strongly acidic. A substance V that reacts with both strong acids and strong bases is amphoteric.

*a) (iii) One substance that shows amphoteric characteristics is zinc oxide ($\text{ZnO}$). Other examples include aluminium oxide ($\text{Al}_2\text{O}_3$) or lead(II) oxide ($\text{PbO}$).

The conductivity of metals decreases with an increase in temperature because the metal ions (or atoms) in the lattice vibrate more vigorously at higher temperatures. These increased vibrations cause more frequent collisions with the delocalized electrons, impeding their free flow and thus increasing electrical resistance and decreasing conductivity.

To separate sodium chloride ($\text{NaCl}$) from copper(II) oxide ($\text{CuO}$):

1. Add distilled water to the mixture and stir. Sodium chloride is soluble in water, while copper(II) oxide is insoluble.
2. Filter the mixture. The insoluble copper(II) oxide will remain on the filter paper as a residue, and the sodium chloride solution will pass through as the filtrate.
3. Wash the copper(II) oxide residue with a small amount of distilled water and dry it.
4. Heat the sodium chloride solution (filtrate) gently to evaporate the water. The sodium chloride will crystallize out.
5. Collect the dry sodium chloride crystals.

*a) Name B: Condenser

*b) The name given to this method of separation of mixtures is distillation (or simple distillation).