Chapter 7, Problem 7STP

Interpretation Introduction

Interpretation:

The incorrect melting point of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$ is to be identified.

Concept introduction:

The melting point is the temperature at which the substances changes from solid to liquid. The melting of ionic compounds needs the addition of greater amounts of energy in order to break the ionic bonds.

Answer to Problem 7STP

Option C is the correct answer as it is theincorrect melting point regarding chromium (III) oxide.

Explanation of Solution

Reason for correct option:

As ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$ have high melting and boiling point because the oppositely charge ions are bind together by strong attractions between them. Therefore, option C is correct as $148°\text{C}$ is too low melting point for ionic solid.

Conclusion

Reason for incorrect option:

1. $2375°\text{C}$. This melting point is consistent with the melting point of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$, because it has high melting point. Therefore, option A is incorrect answer.
2. $950°\text{C}$. This melting point is consistent with the melting point of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$, because it has high melting point due to the strong attraction between the oppositely charged ion. Therefore, option B is incorrect answer.
3. $3342°\text{C}$. This melting point is consistent with the melting point of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$, because it has high melting point due to the strong attraction between the oppositely charged ion. Therefore, option D is also incorrect answer.