CHE201 Midterm Subjective Guess Paper 2024 by Sulman Ali

CHE-201 · SUBJECTIVE MIDTERM- 100% · GUESS PAPER 2024 · Physical Chemistry · BY SULMAN ALI · SUBJECTIVES · Importance of 3rd law of thermodynamics:

1= It helps in calculating the thermodynamic properties. 2= It is helpful in measuring chemical affinity. Because of this it is known as Nernst theorem. 3= It explains the behavior of solids at very low temperature. 4= It helps in analyzing chemical and phase equilibrium.

Applications of Henry law

Applicability of Henry's Law:

•  Henry's law only works if the molecules are at equilibrium.
•  Henry's law does not work for gases at high pressures (e.g., N2(g) at high pressure becomes very soluble and harmful when in the blood supply).
•  Henry's law does not work if there is a chemical reaction between the solute and solvent (e.g., HCl(g) reacts with water by a dissociation reaction to generate H3O and Cl- ions).

Write some factors that cause a process to become irreversible. / Why does a process become irreversible?

1= Friction, 2= Unrestrained expansion and compression, 3= Mixing, 4= Heat transfer (finite ΔT), 5= Inelastic deformation, 6= Chemical reactions.

Describe Mass Percent, Volume Percent, Mass/Volume Percent:

1. Mass Percent: The mass percent is used to express the concentration of a solution when the mass of a solute and the mass of a solution is given:
2. Volume Percent: The volume percent is used to express the concentration of a solution when the volume of a solute and the volume of a solution is given:
3. Mass/Volume Percent: Another version of a percentage concentration is mass/volume percent, which measures the mass or weight of solute in grams (e.g., in grams) vs. the volume of solution (e.g., in mL).

Example: For a solution with 10 grams of salt in 100 mL of water, the mass/volume percent is:

Equilibrium thermodynamics:

Equilibrium thermodynamics studies systems in a state of equilibrium, focusing on macroscopic properties without relying on molecular theories. It analyzes energy, work, and heat exchanges within a system at equilibrium, ensuring no net change occurs over time. This field contrasts with non-equilibrium thermodynamics, which deals with processes and systems not in equilibrium.

Three types of Equilibrium thermodynamics:

Mechanical Equilibrium: No unbalanced forces act on or within the system; hence the system undergoes no acceleration, and there is no turbulence within the system.

Material Equilibrium: No net chemical reactions are occurring in the system, nor is there any net transfer of matter from one part of the system to another or between the system and its surroundings.

Thermal Equilibrium between a system and its surroundings, there must be no change in the properties of the system or surroundings when they are separated by a thermally conducting wall. For thermodynamic equilibrium, all three kinds of equilibrium must be present.

Differentiate between open, closed and isolated system?

The macroscopic part of the universe under study in thermodynamics is called the System. The parts of the universe that can interact with the system are called the surroundings. 1= Open system is one where transfer of matter between system and surroundings can occur.2= Closed system is one where no transfer of matter can occur between system and surroundings. 3= Isolated system is one that does not interact in any way with its surroundings. An isolated system is obviously a closed system, but not every closed system is isolated.

Carbon dioxide is polar or non-polar Explain:

CO2 is non-polar. Despite having polar C=O bonds with the central carbon positively charged and outer oxygens negatively charged, the molecule's linear structure causes the bond dipoles to cancel each other out, resulting in a net zero dipole moment (p=0). Thus, the overall molecule has no polarity.

Ideal gas equation and how it can be corrected:

Describe Le Chatelier's Principle and reaction to temperature, pressure:

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium will move to counteract the change. This applies to changes in concentration, pressure, and temperature.

Reaction to Temperature

If the temperature increases, the equilibrium shifts to favor the endothermic reaction, absorbing excess heat. If the temperature decreases, the equilibrium shifts to favor the exothermic reaction, releasing heat.

Reaction to Pressure

For gas reactions, increasing pressure shifts equilibrium toward the side with fewer gas molecules, reducing pressure. Decreasing pressure shifts it toward the side with more gas molecules, increasing pressure.

Write the application of equilibrium constant;

1. Extent of Reaction:

o A large K means high product concentration; reaction proceeds to the right.

o A small K means high reactant concentration; reaction proceeds to the left.

2. Direction Prediction:

o If Q=Kc, system is at equilibrium.

o If Q> Kc, reaction proceeds left.

o If Q< Kc, reaction proceeds right.

3. Equilibrium Concentration Calculation:

o Determines the concentration of reactants or products at equilibrium.

Define the following terms. 1= critical volume, 2= critical pressure, 3= critical temperature:

The Critical Volume: The volume occupied by a unit mass of a gas or vapors in its critical states.

The Critical Pressure: The pressure required to liquefy a gas at its critical temperature.

The Critical Temperature: The temperature at and above which vapors of the substance cannot be liquefied, no matter how much pressure is applied.

Why ions occur in polar and non-polar with dipole moment

Reason for Ion Occurrence in Polar and Non-Polar Molecules with Dipole Moments

Polarity and Dipole Moments: Ions occur in polar molecules due to unequal electron sharing, creating a dipole moment (μ=Q×r). Non-polar molecules, being symmetric, have dipole moments that cancel out, resulting in no net dipole. Thus, polar molecules have net dipole moments, while non-polar ones do not.

How viscosity is measured by Ostwald’s viscometer?

Ostwald Viscometer: