Would you expect TiO2 or CO2 to have the highest melting point?

Answer 1

TiO2. If you don't know that TiO2 is a solid and CO2 is a gas the "reasoning"is

TiO2 is a metal oxide, these are solids. CO2 is a non-metal oxide and carbon is not a metalloid, and the majority of these are gases (SeO2 is the exception.

Additionally, you can look at their electronegativity differences and see that titanium(IV) oxide is more ionic and carbon dioxide is more covalent. Generally speaking, ionic solids have high melting points and covalent substances (mostly gases and liquids anyway under normal conditions) have low melting points.

Answer 2

TiO2 (titanium dioxide) would be expected to have a higher melting point compared to CO2 (carbon dioxide) because TiO2 is an ionic compound with stronger bonds between atoms, leading to a higher melting point compared to CO2, which is a simple molecular compound with weaker intermolecular forces.