Answer:
According to Coulomb’s law, the Ca and Se ions have 4 times the attractive force (2+ × 2-) than that of the K and Br ions (1+ × 1-).
Explanation:
From Coulomb's law, the attractive force between calcium and selenium ions is four times the attractive force between potassium and bromide ions.
This has something to do with size and magnitude of charge. Calcium ions and selenide ions are smaller and both carry greater charge magnitude than potassium and bromide ions. This paves way for greater electrostatic attraction between them when the distance of the charges apart is minimal. Hence a greater lattice energy.
The wick and the wax
Sorry if that was useless, I'm not sure how generalized you were being
Iron filings can be attracted by the magnet whereas salt can not. So the mixture can be separated by a magnet
2 Al+ 3 CuO-> 1 Al2O3+ 3Cu
