Q: A gas expands against a constant external pressure, doing 150 J of work on the surroundings and absorbing 200 J of heat. What is the change in internal energy ($$\Delta U) of $$the system?

$$\Delta U = 200\ \text{J} + (-150\ \text{J}) = 50\ \text{J}$$

Q: Which of the following processes results in the greatest increase in entropy ($$\Delta S$$)?

Sublimation of dry ice ($$\text{CO}_2$$ solid $$\rightarrow$$ $$\text{CO}_2$$ gas)

Q: A reaction has $$\Delta H = +40\ \text{kJ}$$ and $$\Delta S = +120\ \text{J/K}. At $$what temperature will the reaction become spontaneous?

When $$T \u003e \frac{\Delta H}{\Delta S} = \frac{40,000\ \text{J}}{120\ \text{J/K}} = 333\ \text{K}$$

Q: Which photon has the highest energy?

A photon with wavelength $$200\ \text{nm}$$

Q: What is the frequency ($$\nu) of $$light with a wavelength ($$\lambda) of$$ $$500\ \text{nm}$$? (Speed of light $$c = 3.00 \times 10^8$\ \text{m/s})$$

$$\nu = \frac{c}{\lambda} = \frac{3.00 \times 10^8$}{5.00 \times 10$$^{-7}$$} = 6.00 \times 10$$^{14}$$\ \text{Hz}$$

Q: Which process is exothermic and increases the entropy of the system?

Combustion of methane: $$\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} ($$gases)

Question 1

Which of the following statements best distinguishes between heat and temperature?

Accepted Answer

Heat is the energy transferred between objects due to a temperature difference, while temperature is a measure of the average kinetic energy of particles.

Question 2

A gas expands against a constant external pressure, doing 150 J of work on the surroundings and absorbing 200 J of heat. What is the change in internal energy ($$\Delta U) of $$the system?

Accepted Answer

$$\Delta U = 200\ 	ext{J} + (-150\ 	ext{J}) = 50\ 	ext{J}$$

Question 3

Which of the following processes results in the greatest increase in entropy ($$\Delta S$$)?

Accepted Answer

Sublimation of dry ice ($$	ext{CO}_2$$ solid $$ightarrow$$ $$	ext{CO}_2$$ gas)

Question 4

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 5

A reaction has $$\Delta H = +40\ 	ext{kJ}$$ and $$\Delta S = +120\ 	ext{J/K}. At $$what temperature will the reaction become spontaneous?

Accepted Answer

When $$T \u003e \frac{\Delta H}{\Delta S} = \frac{40,000\ 	ext{J}}{120\ 	ext{J/K}} = 333\ 	ext{K}$$

Question 6

Which of the following best describes the Second Law of Thermodynamics?

Accepted Answer

All spontaneous processes result in an increase in the entropy of the universe ($$\Delta S_{	ext{univ}} \u003e 0).$$

Question 7

Which combination of $$\Delta H$$ and $$\Delta S$$ guarantees a reaction is spontaneous at all temperatures?

Accepted Answer

$$\Delta H  0$$

Question 8

Which photon has the highest energy?

Accepted Answer

A photon with wavelength $$200\ 	ext{nm}$$

Question 9

What is the frequency ($$
u) of $$light with a wavelength ($$\lambda) of$$ $$500\ 	ext{nm}$$? (Speed of light $$c = 3.00 	imes 10^8$\ 	ext{m/s})$$

Accepted Answer

$$
u = \frac{c}{\lambda} = \frac{3.00 	imes 10^8$}{5.00 	imes 10$$^{-7}$$} = 6.00 	imes 10$$^{14}$$\ 	ext{Hz}$$

Question 10

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 11

How many total nodes are present in a 4p orbital?

Accepted Answer

$$n-1 = 4-1 = 3$$ nodes

Question 12

Which electron configuration represents the ground state of sulfur (S, $$Z=16$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^4$$

Question 13

Which of the following ions is largest in size?

Accepted Answer

$$	ext{S}^{2-}$$

Question 14

Which element has the highest first ionization energy?

Accepted Answer

Neon ($$	ext{Ne})$$

Question 15

Which process is exothermic and increases the entropy of the system?

Accepted Answer

Combustion of methane: $$	ext{CH}_4 + 2	ext{O}_2 ightarrow 	ext{CO}_2 + 2	ext{H}_2	ext{O} ($$gases)

Question 16

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations have fewer electrons, resulting in decreased electron-electron repulsion and a smaller radius.

Question 17

Which of the following statements about electron affinity is correct (using the course definition)?

Accepted Answer

Electron affinity is the energy released when an electron is added to a neutral atom.

Question 18

A reaction has $$\Delta H = -50\ 	ext{kJ}$$ and $$\Delta S = -100\ 	ext{J/K}. At $$what temperature is the reaction spontaneous?

Accepted Answer

At low temperatures, since $$\Delta G = \Delta H - T\Delta S$$ and both are negative.

Question 19

Which of the following best describes the shape of a d orbital?

Accepted Answer

Clover-shaped

Question 20

Which rule explains why electrons fill degenerate orbitals singly before pairing?

Accepted Answer

Hund's Rule

General Chemistry Exam Review: Thermodynamics, Quantum Theory, and Periodic Trends

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