Q: A microwave oven emits radiation with a frequency of $$2.45 \times 10$$^{9}$$\ \mathrm{Hz}. $$Calculate the wavelength of this radiation in meters.

$$1.22 \times 10$$^{-1}$$\ \mathrm{m}$$

Q: Calculate the difference in energy (in joules per photon) between the $$n = 5$$ and $$n = 2$$ levels of the hydrogen atom. Indicate whether energy is absorbed or released during the transition from $$n = 5 to$$ $$n = 2.$$

$$4.58 \times 10$$^{-19}$$\ \mathrm{J}$$; energy is released.

Q: A photon has a wavelength of $$410\ \mathrm{nm}. $$Calculate its energy (in joules per photon).

$$4.84 \times 10$$^{-19}$$\ \mathrm{J}$$

Q: Using the de Broglie equation, calculate the wavelength of an electron moving at $$2.50 \times 10$$^{6}$$\ \mathrm{m/s}$$ ($$m_e = 9.11 \times 10$$^{-31}$$\ \mathrm{kg}).$$

$$2.91 \times 10$$^{-10}$$\ \mathrm{m}$$

Question 1

A solution is prepared by dissolving 7.25 g of cobalt(II) sulfate (CoSO$$_4$$, molar mass 154.99 g/mol) in enough water to make 275.0 mL of solution. What is the molar concentration of sulfate ions ($$\ce{SO4$$^{2-}$$}) in $$the solution?

Accepted Answer

$$0.169\ \mathrm{M}$$

Question 2

A 300.0 mL sample of a KOH stock solution is diluted to 600.0 mL. The diluted solution is found to have a concentration of $$0.210\ \mathrm{M}. $$What was the concentration of the original stock solution?

Accepted Answer

$$0.420\ \mathrm{M}$$

Question 3

When 50.0 mL of $$0.450\ \mathrm{M}$$ calcium chloride is mixed with 75.0 mL of $$0.300\ \mathrm{M}$$ sodium sulfate, a precipitate forms. What is the mass (in grams) of calcium sulfate ($$\ce{CaSO4}$$, molar mass $$136.14\ \mathrm{g/mol}) $$produced?

Accepted Answer

$$1.53\ \mathrm{g}$$

Question 4

Which of the following is the correct net ionic equation for the reaction between aqueous sodium carbonate and barium nitrate?

Accepted Answer

$$\ce{Ba$$^{2+}$$(aq) + CO_3$^{2-}(aq) \rightarrow $$BaCO_3$$(s)}$$

Question 5

Which of the following ions is a spectator ion in the reaction between acetic acid and sodium hydroxide?

Accepted Answer

$$\ce{Na^+}$$

Question 6

According to the Brønsted–Lowry definition, what role does ammonia ($$\ce{NH_3$}) $$play when reacting with water?

Accepted Answer

It acts as a Brønsted–Lowry base by accepting a proton.

Question 7

What is the pH of an aqueous solution containing $$3.50 	imes 10$$^{-4}$$\ \mathrm{M}$$ $$\ce{Ba(OH)_2}$$?

Accepted Answer

$$12.85$$

Question 8

What mass of HCl (molar mass $$36.46\ \mathrm{g/mol}) $$would be required to exactly neutralize $$35.0\ \mathrm{mL} of$$ $$2.10\ \mathrm{M}$$ NaOH?

Accepted Answer

$$2.69\ \mathrm{g}$$

Question 9

In the reaction $$\ce{Zn(s) + $$CuSO_4$$(aq) \rightarrow $$ZnSO_4$$(aq) + Cu(s)}$$, which species is oxidized, which is reduced, and what are the oxidizing and reducing agents?

Accepted Answer

Zn is oxidized, Cu$$^{2+} is $$reduced; Zn is the reducing agent, Cu$$^{2+} is $$the oxidizing agent.

Question 10

A microwave oven emits radiation with a frequency of $$2.45 	imes 10$$^{9}$$\ \mathrm{Hz}. $$Calculate the wavelength of this radiation in meters.

Accepted Answer

$$1.22 	imes 10$$^{-1}$$\ \mathrm{m}$$

Question 11

Calculate the difference in energy (in joules per photon) between the $$n = 5$$ and $$n = 2$$ levels of the hydrogen atom. Indicate whether energy is absorbed or released during the transition from $$n = 5 to$$ $$n = 2.$$

Accepted Answer

$$4.58 	imes 10$$^{-19}$$\ \mathrm{J}$$; energy is released.

Question 12

A photon has a wavelength of $$410\ \mathrm{nm}. $$Calculate its energy (in joules per photon).

Accepted Answer

$$4.84 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 13

Using the de Broglie equation, calculate the wavelength of an electron moving at $$2.50 	imes 10$$^{6}$$\ \mathrm{m/s}$$ ($$m_e = 9.11 	imes 10$$^{-31}$$\ \mathrm{kg}).$$

Accepted Answer

$$2.91 	imes 10$$^{-10}$$\ \mathrm{m}$$

Question 14

Which of the following sets of quantum numbers is NOT allowed?

Accepted Answer

$$n = 3,\ l = 3,\ m_l = 0,\ m_s = -\frac{1}{2}$$

Question 15

Which element has a valence electron configuration of $$3s^2$$ $$3p^1$$? What is its group number?

Accepted Answer

Aluminum (Al), Group 13

Question 16

The chromium atom does not follow the expected filling order predicted by the Aufbau principle. What is its actual electron configuration and why does it differ?

Accepted Answer

Actual configuration: $$[\mathrm{Ar}]\ 4s^1$\ 3d^5$; it differs because half-filled d$ subshells are more stable.

Question 17

Which of the following statements about atomic structure is correct?

Accepted Answer

Electrons in atoms have both wave and particle properties.

Question 18

What is meant by a node in an orbital? How does the number of nodes relate to the principal quantum number $$n$$?

Accepted Answer

A node is a region where the probability of finding an electron is zero; the number of nodes equals $$n-1.$$

General Chemistry Study Guide: Solutions, Acid-Base, Redox, Atomic Structure, and Quantum Mechanics

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