Question

The values of conductivity of some materials at \( 298.15 \, \text{K} \) in \( \text{S m}^{-1} \) are:
\( 2.1 \times 10^3, \, 1.0 \times 10^{-16}, \, 1.2 \times 10^1, \, 3.91, \, 1.5 \times 10^{-2}, \, 1 \times 10^{-7}, \, 1.0 \times 10^3 \).
The number of conductors among the materials is ______.

Answer 1

Correct Answer: 4

The materials can be categorized as conductors, insulators, and semiconductors based on their conductivity values at 298.15 K.

Conductors generally have conductivities on the order of \(10^2\) to \(10^6 \, \text{S m}^{-1}\).
Insulators have very low conductivities, typically around \(10^{-10}\) to \(10^{-8} \, \text{S m}^{-1}\).
Semiconductors have conductivities ranging from \(10^{-4}\) to \(10 \, \text{S m}^{-1}\).

Given values:

\[ 2.1 \times 10^3, \, 1.2 \times 10^3, \, 3.91, \, 1.5 \times 10^{-2}, \, 1 \times 10^{-7}, \, 1.0 \times 10^3 \]

Classifying each:

• \(2.1 \times 10^3, \, 1.2 \times 10^3, \, \text{and} \, 1.0 \times 10^3\) are in the conductor range.
• \(3.91\) also falls within the conductor range (upper range of semiconductors).
• \(1.5 \times 10^{-2}\) represents a semiconductor.
• \(1 \times 10^{-7}\) represents an insulator.

Therefore, the number of conductors is: 4.