Substance X melts at 80.5oC and boils at 218oC, and the solid form is less dense the it liquid. Which of the following phase diagrams represent the phase diagram of this substance?


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Step 1 of 2

Given data: 6 Multiple choice questions are given with answer options on thermodynamics.

Find: To find the correct option from the given options.

Explanation:

Enthalpy in thermodynamic process helps to measure the energy content in any process.

Step 2 of 2

  1. Based on this description, the phase diagram of this substance would have the following characteristics:
  • The phase diagram would have a solid-liquid line slanting upward from left to right, indicating that the substance’s melting point is below its boiling point.
  • The solid-liquid line would have a negative slope, indicating that the solid form is less dense than the liquid form.
  • The phase diagram would also have a vaporization curve (liquid-gas line) slanting upward from left to right, indicating the boiling point of the substance.

Therefore, the phase diagram of this substance would be similar to a typical phase diagram, with a solid-liquid line and a liquid-gas line, but with the solid-liquid line having a negative slope to indicate that the solid form is less dense than the liquid form.

If solid phase is less denser than liquid , the line that separate solid and liquid bends left.

So from the above stated concept option b is the correct answer.

  1. This can be calculated from the equation of Phase=mcmΔT
  2. Solid Phase (I): The substance is initially in the solid phase. During this phase, the temperature rises until it reaches the melting point.
  3. Melting (II): At the melting point, the substance undergoes a phase transition from solid to liquid. During this transition, the temperature remains constant.
  4. Liquid Phase (III): Once the substance is entirely in the liquid phase, the temperature rises again until it reaches the boiling point.
  5. Boiling (IV): At the boiling point, the substance undergoes another phase transition from liquid to gas. During this transition, the temperature remains constant.
  6. Gas Phase (V): Once the substance is entirely in the gas phase, the temperature rises further.

So the correct answer is option b which is 0.5kJg°c.

3.A heating curve typically consists of several segments:

  • Solid phase: At the beginning of the heating curve, the substance is in the solid phase. As heat is applied, the temperature of the substance gradually increases. The specific heat capacity of the solid phase (denoted as Cs) would determine how much heat is required to raise the temperature of the substance. The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of one gram of the substance by one degree Celsius (or one Kelvin).
  • Melting point: Once the substance reaches its melting point, the temperature remains constant during the phase change from solid to liquid. The heat being absorbed during this phase change is used to break the intermolecular forces holding the solid together rather than increasing the temperature. The specific heat capacity during this phase change is known as the heat of fusion (denoted as ΔHfus). It represents the amount of heat energy required to convert one gram of the solid into the liquid phase at the melting point.
  • Liquid phase: After the substance has completely melted, further heating causes the temperature of the liquid to increase. The specific heat capacity of the liquid phase (denoted as Cl) would determine how much heat is required to raise the temperature of the substance.
  • Boiling point: When the substance reaches its boiling point, the temperature remains constant during the phase change from liquid to gas. The heat being absorbed during this phase change is used to break the intermolecular forces holding the liquid together rather than increasing the temperature. The specific heat capacity during this phase change is known as the heat of vaporization (denoted as ΔHvap). It represents the amount of heat energy required to convert one gram of the liquid into the gas phase at the boiling point.

The correct answer for the question is b. which is 20kJmol.

  1. In a given volume, at the same temperature and pressure, gases contain an equal number of molecules. This is due to the fact that the ideal gas law (PV=�RT) relates the pressure (P), volume (V), number of moles (n), and temperature (T) of a gas. Since the conditions for both N2 and Ar are the same in this scenario, they would have an equal number of molecules in their respective flasks.

 

The given statement is False as from the ideal gas equation which is PV=nRT, when pressure , volume and temperature afre same then the number of molecules will also be same.

 

  1. The process that occurs when the temperature of a substance is decreased at constant pressure until the substance is at Point A is e. freezing.

 

Freezing is the process in which a substance changes from the liquid phase to the solid phase as its temperature decreases. During freezing, the molecules of the substance lose energy, slow down, and arrange themselves into a more ordered and rigid structure, forming a solid.

 

In this scenario, as the temperature of the substance decreases from Point B to Point A, it indicates a transition from a higher temperature liquid phase to a lower temperature solid phase. This transition is characteristic of freezing.

Therefore, the correct answer is freezing.

  1. To determine the molar heat of vaporization (ΔHvap) of substance Z from the given heating curve, we need to identify the phase change associated with vaporization and calculate the amount of heat added during that phase change.

Looking at the heating curve, we can observe that substance Z undergoes a phase change from liquid to gas (vaporization) between approximately 100°C and 125°C. During this phase change, the temperature remains constant as heat is absorbed to break the intermolecular forces and convert the substance from the liquid phase to the gas phase.

To calculate the molar heat of vaporization, we need to determine the amount of heat added during this phase change. From the heating curve, we can see that the heat added during the vaporization process is approximately 800kJ.

Therefore, the molar heat of vaporization (ΔHvap) of substance Z is 800 kJmol−1

.Hence, the correct answer is 800 kJmol−1

Explanation:

Hence we are able to find the answers.

Final solution
  1. option b
  2. b which is 0.5kJ/g°c.
  3. b. which is 20kJ/mol.
  4. False
  5. e. which is Freezing
  6. c which is 800KJ/mol.

 

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