Q: Which of the following is the correct formula for calculating the enthalpy change of a reaction using standard enthalpies of formation?

$$\Delta H_{rxn}^\circ = \sum n_p \Delta H_f^\circ (\text{products}) - \sum n_r \Delta H_f^\circ (\text{reactants})$$

Q: How many photons are in a green light flash (525 nm) containing 189 kJ of energy? ($$h = 6.626 \times 10$$^{-34}$$ J$$\cdot$$s, c = 3.00$$ \times $$10^8 m/s)$$

$$4.99 \times 10$$^{23}$$ photons

Question 1

Which of the following correctly explains why cesium (Cs) has a larger atomic radius than xenon (Xe)?

Accepted Answer

Cs has electrons in a higher principal energy level ($$n$$), resulting in a larger atomic radius.

Question 2

A student observes a red flame during a flame test. Which element is most likely present, and what is the cause of the observed color?

Accepted Answer

Lithium; electrons are excited and emit photons as they return to lower energy levels.

Question 3

Which of the following best describes the process and sign conventions when a system absorbs heat from the surroundings and does work on the surroundings?

Accepted Answer

$$q = +$$, $$w = -$$

Question 4

Calculate the energy change ($$\Delta E) $$for a system that absorbs 150 J of heat and has 75 J of work done on it by the surroundings.

Accepted Answer

$$\Delta E = 225 J$$

Question 5

A 50.0 g sample of water is heated from $$20.0^\circC to$$ $$70.0^\circC. $$Calculate the amount of heat absorbed by the water. ($$C_s = 4.18 J/g$\cdot^\circC)$$

Accepted Answer

$$q = 10,450 J$$

Question 6

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

Accepted Answer

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

Question 7

A mercury lamp emits blue light with a frequency of $$6.88 	imes 10$$^{14}$$ Hz. What is the wavelength of this light in nanometers?

Accepted Answer

$$436 nm$$

Question 8

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 9

Which of the following processes is exothermic?

Accepted Answer

Condensation of water vapor

Question 10

A balloon is inflated from $$0.0100 L to$$ $$0.600 L $$against an external pressure of $$10.00$$ atm. Calculate the work done (in J). ($$1 L$\cdot$$atm $$= 101.3 J)$$

Accepted Answer

$$-598 J$$

Question 11

Which of the following electron configurations represents the ground state of $$\mathrm{Ti$$^{2+}$$}$$?

Accepted Answer

$$[\mathrm{Ar}]3d^2$

Question 12

Which set lists the elements in order of increasing first ionization energy ($$IE_1$$)?

Accepted Answer

As \u003c N \u003c F

Question 13

Which of the following is the correct formula for calculating the enthalpy change of a reaction using standard enthalpies of formation?

Accepted Answer

$$\Delta H_{rxn}^\circ = \sum n_p \Delta H_f^\circ (	ext{products}) - \sum n_r \Delta H_f^\circ (	ext{reactants})$$

Question 14

How many photons are in a green light flash (525 nm) containing 189 kJ of energy? ($$h = 6.626 	imes 10$$^{-34}$$ J$$\cdot$$s, c = 3.00$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$4.99 	imes 10$$^{23}$$ photons

Question 15

Which of the following quantum numbers is associated with the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number ($$m_l)$$

Question 16

Which of the following best defines heat capacity?

Accepted Answer

The quantity of heat required to change a system's temperature by $$1^\circC$$

Question 17

Which of the following is the correct set of possible $$m_l$$ values for a d orbital?

Accepted Answer

$$-2, -1, 0, +1, +2$$

Question 18

Which of the following elements has the greatest metallic character?

Accepted Answer

Potassium (K)

Question 19

A 100.0 mL sample of 0.300 M NaOH is mixed with a 100.0 mL sample of 0.300 M HNO$$_3 in a $$coffee cup calorimeter. The temperature rises from $$35.00^\circC to$$ $$37.00^\circC. $$Assuming the density and heat capacity are the same as water, what is $$\Delta H_{rxn} (in kJ/$$mol NaOH) for the neutralization reaction?

Accepted Answer

$$-55.7 kJ/$$mol NaOH

Question 20

Which of the following is the correct ground state electron configuration for lead (Pb)?

Accepted Answer

$$[\mathrm{Xe}]6s^24$f^{14}5d$$^{10}$$6p^2$

General Chemistry Practice Exam 3 – Step-by-Step Study Guidance

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