Question

An unknown substance has a melting point of 1064°C, is insoluble in water, conducts electricity as a solid, and is hard. Given these properties, which of the following are possible identities for the unknown substance?

a. NaBr
b. Cl2
c. SiO2
d. Au

Answer 1

Answer: Option (d) is the correct answer.

Explanation:

NaBr is an ionic compound and it is able to conduct electricity only when it is dissolved in water. This is because then it will form ions. And, electricity is the flow of ions or electrons.

$Cl_{2}$ is a gas and it is made up of a non-metal. And, non-metals are poor conductors of heat and electricity therefore, $Cl_{2}$ is unable to conduct electricity.

Also, $SiO_{2}$ is a non-metallic compound therefore, it is unable to conduct electricity.

On the other hand, Au is a metal with a melting point of $1064^{o}C$ and it is insoluble in water and hard in nature. Also, it is able to conduct electricity in solid state.

Thus, we can conclude that Au has the possible identities for the unknown substance.