Chapter 2, Problem 63A

Interpretation Introduction

Interpretation: The colorless substance which is liquid at $-30{}^{\text{o}}\text{C}$ needs to be determined.

Concept Introduction: The melting point is defined as the temperature at which a solid substance starts melting. The boiling point is defined as the temperature of a liquid when its vapor pressure is equal to the atmospheric pressure. This is the temperature when liquid starts boiling and converts into vapor.

Answer to Problem 63A

Ethanol.

Explanation of Solution

From the given data, colorless substances are as follows:

Ethanol, neon, and water.

Here, the melting and boiling point of ethanol is $-117{}^{\text{o}}\text{C}$ and $78{}^{\text{o}}\text{C}$ respectively. Similarly, the melting point and boiling point of neon is $-249{}^{\text{o}}\text{C}$ and $-246{}^{\text{o}}\text{C}$ respectively. The melting point and boiling point of water is $0{}^{\text{o}}\text{C}$ and $100{}^{\text{o}}\text{C}$ respectively.

Here, water cannot be liquid at $-30{}^{\text{o}}\text{C}$ because it is liquid between temperatures $0-100{}^{\text{o}}\text{C}$ . Now, ethanol is liquid and neon is gas at room temperature. Here, the melting point given is the freezing temperature for ethanol thus, it is liquid at $-30{}^{\text{o}}\text{C}$

Thus, the correct answer is ethanol.

Conclusion

Thus, ethanol is liquid at $-30{}^{\text{o}}\text{C}$ .