Q: A photon has a frequency of $$6.0 \times 10$$^{14}$$ Hz. What is its energy?

$$E = h \nu = (6.626 \times 10$$^{-34}$$ \text{J} \cdot \text{s}) \times (6.0 \times 10$$^{14}$$ \text{Hz}) = 3.98 \times 10$$^{-19}$$ \text{J}$$

Q: Based on de Broglie's equation, which particle will have the SMALLEST wavelength?

A baseball moving at $$1 \times 10^6$ m/s

Question 1

A chemical process occurs that releases $$q J of $$heat to the surroundings and does $$w J of $$work on its surroundings. What is the $$	ext{enthalpy}$$ change ($$	riangle H) $$for this process?

Accepted Answer

$$	riangle H = q$$ \,\, (at \,\, constant \,\, pressure)$

Question 2

Which statement about $$	ext{molar enthalpy} is $$CORRECT?

Accepted Answer

It is the enthalpy change per mole of product formed.

Question 3

Which of the following electron configurations is correct for the element with atomic number 17?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^5$$

Question 4

When calculating the enthalpy of formation ($$	riangle H_f^	ext{0}$$), which of the following must you consider?

Accepted Answer

The enthalpy of the products and the reactants, using their stoichiometric coefficients.

Question 5

A photon has a frequency of $$6.0 	imes 10$$^{14}$$ Hz. What is its energy?

Accepted Answer

$$E = h 
u = (6.626 	imes 10$$^{-34}$$ 	ext{J} \cdot 	ext{s}) 	imes (6.0 	imes 10$$^{14}$$ 	ext{Hz}) = 3.98 	imes 10$$^{-19}$$ 	ext{J}$$

Question 6

Which statement about the electromagnetic spectrum is TRUE?

Accepted Answer

Gamma rays have the highest energy and shortest wavelength.

Question 7

According to Hund's rule, when filling degenerate orbitals, electrons will:

Accepted Answer

Occupy separate orbitals with parallel spins before pairing.

Question 8

Based on de Broglie's equation, which particle will have the SMALLEST wavelength?

Accepted Answer

A baseball moving at $$1 	imes 10^6$ m/s

Question 9

For a reaction: $$2A + 3B \rightarrow 4C$$, if you are given the enthalpy change for the reaction as written, but asked for the enthalpy change per mole of $$C$$ produced, what should you do?

Accepted Answer

Divide the enthalpy change by 4.

Question 10

Which quantum number determines the shape of an orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 11

Which of the following transitions in a hydrogen atom will release the MOST energy?

Accepted Answer

From $$n=2 to$$ $$n=1$$

Question 12

Two electrons in the same orbital must have:

Accepted Answer

Opposite spin quantum numbers ($$m_s)$$

Question 13

Which of the following best explains why energy is released when two oppositely charged particles move closer together?

Accepted Answer

The system's potential energy decreases.

Question 14

If you are given the energy of a photon, how do you determine its wavelength?

Accepted Answer

$$\lambda = \dfrac{hc}{E}$$

Question 15

Which of the following statements about bond formation is TRUE?

Accepted Answer

Bond formation is always exothermic.

Question 16

In a calorimetry experiment, why must you take the mass of your salt and divide by its molar mass when calculating moles?

Accepted Answer

To convert grams to moles for stoichiometric calculations.

Question 17

For a single electron system (hydrogen atom), all orbitals with a shell $$n$$ have the same energy. What happens in multi-electron systems?

Accepted Answer

Orbitals with the same $$n$$ but different $$l$$ have different energies.

Question 18

A reaction yields 0.200 mol of product A. If the molar enthalpy of formation of A is $$-200 kJ/$$mol, what is the enthalpy change for this reaction?

Accepted Answer

$$-40 kJ$$

Exam 3 Review: Key Takeaways in Thermochemistry and Electronic Structure

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