A solid substance with high melting and boiling points is likely to be a. a covalent compound b. a dative covalent compound c. an ionic compound d. a non-metal

Here are the solutions to the questions:

1. A solid substance with high melting and boiling points is likely to be a. a covalent compound b. a dative covalent compound c. an ionic compound d. a non-metal

• Explanation: Ionic compounds are characterized by strong electrostatic forces between oppositely charged ions, which require a large amount of energy to overcome, resulting in high melting and boiling points.
• Answer: $\boxed{\text{c. an ionic compound}}$

2. Which of the following compounds has coordinate bonds in its structure? a. Al₂O₃ b. MgO₂ c. AgCl d. NaCl

• Explanation: This question is problematic as none of the given simple binary compounds typically contain coordinate bonds in their standard structures.