Predict which compound in each pair will have the higher melting point, and explain why for each pair. (a) HI or KI (b) \(\mathrm{Na}_{2} \mathrm{O}\) or \(\mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{CaF}_{2}\) or \(\mathrm{HF}\) (d) \(\mathrm{SiO}_{2}\) or \(\mathrm{CO}_{2}\)

(a) KI will have a higher melting point than HI as ionic compounds have stronger electrostatic forces compared to covalent molecules. (b) \(\mathrm{Na}_{2} \mathrm{O}\) will have a higher melting point than \(\mathrm{H}_{2} \mathrm{O}\) because ionic compounds have stronger attractive forces compared to molecular compounds. (c) \(\mathrm{CaF}_{2}\) will have a higher melting point than \(\mathrm{HF}\) since the ionic bonds in \(\mathrm{CaF}_{2}\) are stronger than the hydrogen bonds in \(\mathrm{HF}\). (d) \(\mathrm{SiO}_{2}\) will have a higher melting point than \(\mathrm{CO}_{2}\) due to its giant covalent structure with strong covalent bonds, while \(\mathrm{CO}_{2}\) has weaker dispersion forces between its molecules.