Chemistry MCQ Practice

Both magnesium oxide, MgO, and aluminium oxide, Al₂O₃, are solids at room temperature, 25 °C.

 

MgO has a melting point of 2852 °C and a boiling point of 3600 °C.

 

Al₂O₃ has a melting point of 2072 °C and a boiling point of 2880 °C.

 

Over which temperature range will both pure compounds conduct electricity?

 

A)  25 to 2852 °C

 

B)  2072 to 2852 °C

 

C)  2852 to 2880 °C

 

D)  2880 to 3600 °C

 

 

Answer: C

 

Both oxides are ionic compounds. Ionic compounds can only conduct electricity when molten (liquid) or aqueous.

 

The range of temperatures where both compounds can conduct electricity would be where both compounds exist as liquids.

 

The construction of a number line is very useful for questions like this.