Q: According to Hess's Law, which equation correctly represents the enthalpy change for a reaction?

$$\Delta H_{\text{rxn}} = \sum \Delta H_{\text{products}} - \sum \Delta H_{\text{reactants}}$$

Q: What is the wavelength of an electron moving at $$2.0 \times 10^6$\ \text{m/s}$$? (Mass of electron $$= 9.11 \times 10$$^{-31}$$\ \text{kg}$$, Planck's constant $$h = 6.63 \times 10$$^{-34}$$\ \text{J} \cdot \text{s})$$

$$\lambda = 3.6 \times 10$$^{-10}$$\ \text{m}$$

Question 1

A chemical reaction releases 150 kJ of heat to the surroundings and does 30 kJ of work on the surroundings. According to the First Law of Thermodynamics, what is the change in internal energy ($$\Delta U) of $$the system?

Accepted Answer

$$\Delta U = -180\ 	ext{kJ}$$

Question 2

Which of the following best describes the relationship between wavelength ($$\lambda$$), frequency ($$
u$$), and the speed of light ($$c$$)?

Accepted Answer

$$c = \lambda 
u$$

Question 3

A calorimeter contains 100 g of water at $$25^\circC. If a $$reaction causes the temperature to rise to $$30^\circC$$, what is the heat absorbed by the water? (Specific heat of water $$= 4.18\ 	ext{J/g} \cdot 	ext{K})$$

Accepted Answer

$$q = 2,090\ 	ext{J}$$

Question 4

Which experiment provided evidence for the wave nature of electrons?

Accepted Answer

Electron diffraction through a crystal

Question 5

Which quantum number determines the shape of an orbital?

Accepted Answer

Azimuthal quantum number ($$l)$$

Question 6

Which of the following elements has the highest effective nuclear charge ($$Z_{	ext{eff}}) $$for its valence electrons?

Accepted Answer

Fluorine

Question 7

Which statement about the photoelectric effect is correct?

Accepted Answer

Electrons are ejected from a metal only if the incident light has a frequency above a threshold value.

Question 8

Which of the following is the correct electron configuration for $$	ext{Fe}^{2+}$$ using noble gas notation?

Accepted Answer

[Ar] $$3d^6$$

Question 9

Which element has the largest atomic radius?

Accepted Answer

Potassium

Question 10

According to Hess's Law, which equation correctly represents the enthalpy change for a reaction?

Accepted Answer

$$\Delta H_{	ext{rxn}} = \sum \Delta H_{	ext{products}} - \sum \Delta H_{	ext{reactants}}$$

Question 11

Which of the following ions has the smallest ionic radius?

Accepted Answer

$$	ext{Al}^{3+}$$

Question 12

What is the wavelength of an electron moving at $$2.0 	imes 10^6$\ 	ext{m/s}$$? (Mass of electron $$= 9.11 	imes 10$$^{-31}$$\ 	ext{kg}$$, Planck's constant $$h = 6.63 	imes 10$$^{-34}$$\ 	ext{J} \cdot 	ext{s})$$

Accepted Answer

$$\lambda = 3.6 	imes 10$$^{-10}$$\ 	ext{m}$$

Question 13

Which of the following transitions in the hydrogen atom emits the highest energy photon?

Accepted Answer

$$n=3 \rightarrow n=1$$

Question 14

Which of the following statements about periodic trends is correct?

Accepted Answer

Ionization energy increases across a period from left to right.

Question 15

Which orbital designation is NOT possible according to quantum numbers?

Accepted Answer

$$3f$$

Question 16

A reaction has $$\Delta H = -200\ 	ext{kJ}$$ and $$\Delta S = -300\ 	ext{J/K}. At $$what temperature will the reaction become non-spontaneous? (Use $$\Delta G = \Delta H - T\Delta S)$$

Accepted Answer

$$T \u003e 667\ 	ext{K}$$

Question 17

Which of the following is an exception to the Aufbau principle in electron configuration?

Accepted Answer

Chromium ($$	ext{Cr})$$

Question 18

Which of the following best describes the difference between system and surroundings in thermodynamics?

Accepted Answer

The system is the part of the universe being studied; the surroundings are everything else.

Question 19

Which property of waves explains why X-rays can be used for medical imaging but visible light cannot?

Accepted Answer

X-rays have much shorter wavelengths, allowing them to penetrate tissues.

Study Guide: Thermochemistry, Quantum Mechanics, and Periodic Trends (Chapters 7–9)

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