Chapter 14, Problem 21A

Interpretation Introduction

Interpretation:

The heating curve is to be constructed from the given data.

Concept introduction:

The temperature at which the solid and liquid states of pure substance exits as equilibrium are called melting point of substance. As heat provide to as solid substance, temperature increases until melt itself. More heat will convert solid to liquid without temperature change. And the heat is to be required to convert unit mass of solid to liquid are called heat of fusion.

The temperature at which vapor pressure of liquid is equal to the atmospheric pressure (surrounding pressure) called boiling point of substance. At this condition, addition of heat results to transform the liquid to vapor without raising temperature. The heat absorbed by the one mole of substance to convert from a liquid to gas physical state is called molar heat of vaporization.

Answer to Problem 21A

The heating curve of substance X is,

  

Explanation of Solution

The state of substance change is physical change. Heat energy provides which increases the vibration motion of the molecule, and increases the kinetic energy of substance. The substance X with melting at ${\text{-15}}^{\text{o}}\text{C}$ and molar heat of fusion is $\text{2}\text{.5 }\frac{\text{kJ}}{\text{mol}}$ . As heat applied to a solid substance X, it’s temperature increases until the ${\text{-15}}^{\text{o}}\text{C}$ and more heat then use to convert solid into liquid which is equilibrium state shows solid and liquid in substance. When all solids melted, additional heat will raise the temperature of the liquid X substance.

The substance X is reached at ${134}^{\text{o}}\text{C}$ with consuming $\text{55}\text{.3 }\frac{\text{kJ}}{\text{mol}}$ of heat. At ${134}^{\text{o}}\text{C}$ vapor pressure of liquid X is equaled to the atmospheric pressure. Further addition of heat results in the conversion of liquid into gaseous state.

Conclusion

Boiling process required more heat than melting.