Q: A 650 g iron cube is heated from 20.0°C to 80.0°C. If the specific heat capacity of iron is $$0.450\ \mathrm{J}/\mathrm{g} \cdot \mathrm{K}$$, how much heat is absorbed?

$$q = mC\Delta T = 650\ \mathrm{g} \times 0.450\ \mathrm{J}/\mathrm{g} \cdot \mathrm{K} \times (80.0 - 20.0)\ \mathrm{K} = 17,550\ \mathrm{J}$$

Q: What is the energy of a photon with a wavelength of 500 nm?

$$E = \dfrac{hc}{\lambda} = \dfrac{6.626 \times 10$$^{-34}$$\ \mathrm{J} \cdot \mathrm{s} \times 3.00 \times 10^8$\ \mathrm{m}/\mathrm{s}}{500 \times 10$$^{-9}$$\ \mathrm{m}} = 3.98 \times 10$$^{-19}$$\ \mathrm{J}$$

Q: What is the energy change when an electron in a hydrogen atom transitions from $$n=3 to$$ $$n=2$$?

$$\Delta E = -2.18 \times 10$$^{-18}$$\ \mathrm{J} \left( \dfrac{1}{2^2$} - \dfrac{1}{3^2$} \right ) = -4.57 \times 10$$^{-19}$$\ \mathrm{J}$$

Question 1

Which statement best describes the First Law of Thermodynamics?

Accepted Answer

The energy of the universe is conserved; energy can be transferred but not created or destroyed.

Question 2

A gas in a piston expands against a constant external pressure of 1.00 atm from 2.00 L to 5.00 L. What is the work done by the gas?

Accepted Answer

$$w = -P_{ext} \Delta V = -(1.00\ \mathrm{atm})(5.00\ \mathrm{L} - 2.00\ \mathrm{L}) = -3.00\ \mathrm{L} \cdot \mathrm{atm}$$

Question 3

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 4

During a chemical reaction at constant pressure, the system absorbs 250 J of heat and does 100 J of work on the surroundings. What is the change in internal energy ($$\Delta E$$)?

Accepted Answer

$$\Delta E = q - w = 250\ \mathrm{J} - 100\ \mathrm{J} = 150\ \mathrm{J}$$

Question 5

Which calorimetry technique is best suited for measuring heat changes at constant volume?

Accepted Answer

Bomb calorimetry

Question 6

A 650 g iron cube is heated from 20.0°C to 80.0°C. If the specific heat capacity of iron is $$0.450\ \mathrm{J}/\mathrm{g} \cdot \mathrm{K}$$, how much heat is absorbed?

Accepted Answer

$$q = mC\Delta T = 650\ \mathrm{g} 	imes 0.450\ \mathrm{J}/\mathrm{g} \cdot \mathrm{K} 	imes (80.0 - 20.0)\ \mathrm{K} = 17,550\ \mathrm{J}$$

Question 7

Which of the following statements about standard enthalpy of formation ($$\Delta H_f^\circ) is $$TRUE?

Accepted Answer

It is the enthalpy change for forming 1 mole of a compound from its elements in their standard states.

Question 8

Which of the following best explains why the photoelectric effect supports the particle nature of light?

Accepted Answer

Electrons are ejected only when the light's frequency exceeds a threshold, regardless of intensity.

Question 9

What is the energy of a photon with a wavelength of 500 nm?

Accepted Answer

$$E = \dfrac{hc}{\lambda} = \dfrac{6.626 	imes 10$$^{-34}$$\ \mathrm{J} \cdot \mathrm{s} 	imes 3.00 	imes 10^8$\ \mathrm{m}/\mathrm{s}}{500 	imes 10$$^{-9}$$\ \mathrm{m}} = 3.98 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 10

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 11

According to Hund's Rule, how are electrons arranged in degenerate orbitals?

Accepted Answer

Electrons fill each orbital singly with parallel spins before pairing.

Question 12

Which of the following electron configurations represents a paramagnetic atom?

Accepted Answer

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

Question 13

What is the energy change when an electron in a hydrogen atom transitions from $$n=3 to$$ $$n=2$$?

Accepted Answer

$$\Delta E = -2.18 	imes 10$$^{-18}$$\ \mathrm{J} \left( \dfrac{1}{2^2$} - \dfrac{1}{3^2$} ight ) = -4.57 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 14

Which statement about the uncertainty principle is correct?

Accepted Answer

The product of uncertainties in position and momentum is always greater than or equal to $$\dfrac{h}{4\pi}.$$

Question 15

Which of the following best describes a path function?

Accepted Answer

A property that depends on the specific process taken between two states.

Question 16

Which of the following reactions is exothermic?

Accepted Answer

$$2\ \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2\ \mathrm{H}_2\mathrm{O}(g)$$

Question 17

Which of the following is TRUE about the relationship between wavelength and frequency of electromagnetic radiation?

Accepted Answer

Wavelength and frequency are inversely proportional: $$c = \lambda 
u$$

Question 18

Which of the following best explains why electrons in multi-electron atoms experience less than the full nuclear charge?

Accepted Answer

Electron-electron repulsion and shielding reduce the effective nuclear charge ($$Z_{eff}).$$

Thermodynamics and Energetics: The First Law and Work in Chemical Systems

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