Question

Question: The melting point of cobalt is 1495°C, and that of barium chloride is 963°C. Rank the four substances in problem 27 from lowest to highest in melting point.

Short answer

The order of melting point is:

$\text{CO}<{\text{BaCl}}_{\text{2}}<\text{Co}<\text{SiC}$

Step-by-step solution

The bonding nature of different given compounds.

The difference in electronegativities makes the compound barium chloride ionic. It has a given melting point of $963°C$.

${\text{Cl}}^{-}{\text{- Ba}}^{2+}{\text{- Cl}}^{-}$

The bonding between silicon and carbon atoms is covalent. The melting point of SiC is around $2700°C$as the compound is very strong.

Carbon monoxide is a molecular crystal where the molecules are packed together without overlapping through Van der Waals forces. It is the weakest kind of bonding among all.

The interactions between the stable ions of cobalt that keep the metal together, and strong ismetallic bonding. There is a sea of mobile electrons found around the fixed ions. Metal is electrically neutral as the density of electrons is similar to that of positively charged ions. The melting point of cobalt is$1495°C$

The rank from lowest to highest in melting point.

Therefore, the strongest bonding is the bonding between silicon and carbon,followed by the metallic bonding of cobalt, the ionic bonding of barium chloride, and finally, the Van der Waals forces of CO.

This makes the order:

$\text{CO}<{\text{BaCl}}_{\text{2}}<\text{Co}<\text{SiC}$