Question 1

Which of the following best describes the internal energy $$U of a $$substance?

Accepted Answer

The sum of kinetic energy of translation, rotation, vibration, potential energy from intermolecular forces, and other molecular energies.

Question 2

According to the first law of thermodynamics, which equation correctly represents the energy balance for a closed system?

Accepted Answer

$$\Delta U = Q + W$$

Question 3

A process is said to be reversible if:

Accepted Answer

It can be reversed at any point by a differential change in external conditions, traversing a succession of equilibrium states.

Question 4

Which of the following statements about equilibrium is correct?

Accepted Answer

Equilibrium is a static condition with no tendency toward change and absence of driving forces.

Question 5

Given the phase rule $$F = 2 - \pi + N$$, where $$F is $$the degrees of freedom, $$\pi is $$the number of phases, and $$N is $$the number of chemical species, what is $$F$$ for a system of liquid water in equilibrium with its vapor?

Accepted Answer

$$F = 1$$

Question 6

Which formula correctly defines enthalpy $$H$$?

Accepted Answer

$$H = U + PV$$

Question 7

The heat capacity at constant volume $$C_v is $$defined as:

Accepted Answer

$$C_v = \left( \frac{\partial U}{\partial T} \right)_V$$

Question 8

For a mechanically reversible process at constant pressure, which equation gives the heat transferred?

Accepted Answer

$$Q = nC_p \Delta T$$

Question 9

An ideal gas undergoes a process at constant volume. Which expression correctly gives the change in internal energy?

Accepted Answer

$$\Delta U = nC_v \Delta T$$

Question 10

A liquid solution of alcohol in water is in equilibrium with its vapor. If there are two chemical species and two phases, what is the number of degrees of freedom according to the phase rule?

Accepted Answer

$$F = 2 - 2 + 2 = 2$$

Question 11

Which of the following is true about the property changes $$\Delta U$$ and $$\Delta H$$ for a given change in state?

Accepted Answer

They depend only on the initial and final states, not on the path.

Question 12

In a real-world scenario, a sealed container with water is heated at constant pressure. Which formula should be used to calculate the heat required?

Accepted Answer

$$Q = nC_p \Delta T$$

Question 13

Which of the following is NOT a component of the internal energy $$U of a $$substance?

Accepted Answer

Energy required to move the system as a whole

Question 14

A process is mechanically reversible if:

Accepted Answer

It occurs infinitely slowly and can be reversed by an infinitesimal change in external conditions.

Question 15

Which of the following best explains why internal energy $$U$$ cannot be directly measured?

Accepted Answer

Because only changes in internal energy are required for analysis, not its absolute value.

Question 16

In the context of thermodynamics, which statement about heat capacity is correct?

Accepted Answer

Heat capacity is greater for substances that experience a smaller temperature change for a given quantity of heat.

Question 17

For an ideal gas, which equation is valid at constant pressure for the change in enthalpy?

Accepted Answer

$$\Delta H = nC_p \Delta T$$

Question 18

Which of the following is a correct statement of the first law of thermodynamics for a closed system?

Accepted Answer

The total energy change of a constant mass system equals the net energy transported into it as heat and work.

Question 19

A mixture of water vapor and nitrogen is in equilibrium. If there are two chemical species and two phases, what is the number of degrees of freedom?

Accepted Answer

$$F = 2$$

CHE 130: Thermodynamics – Core Concepts and Applications

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