Q: Given the speed of light $$c = 3.00 \times 10^8$ m/s and a wavelength $$\lambda = 500$$ nm, what is the frequency $$\nu$$ of this light? Use 1$ nm = 1$$ \times $$10^{-9} m.$$

$$\nu = 6.00 \times 10$$^{14}$$ Hz

Question 1

Which of the following best describes the dual nature of light as understood in modern chemistry?

Accepted Answer

Light exhibits both wave-like and particle-like properties depending on the experiment.

Question 2

Given the speed of light $$c = 3.00 	imes 10^8$ m/s and a wavelength $$\lambda = 500$$ nm, what is the frequency $$
u$$ of this light? Use 1$ nm = 1$$ 	imes $$10^{-9} m.$$

Accepted Answer

$$
u = 6.00 	imes 10$$^{14}$$ Hz

Question 3

Which equation correctly relates the energy $$E of a $$photon to its frequency $$
u$$?

Accepted Answer

$$E = h
u$$

Question 4

How did the observation of atomic emission spectra contribute to the development of the Bohr model of the atom?

Accepted Answer

It revealed that electrons occupy quantized energy levels, emitting photons when transitioning between them.

Question 5

Which set of quantum numbers is not allowed for an electron in an atom?

Accepted Answer

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

Question 6

Which of the following best describes the shape of a $$p$$ orbital?

Accepted Answer

Dumbbell-shaped

Question 7

What is the correct noble gas core electron configuration for $$\mathrm{Ca}^{2+}$$?

Accepted Answer

$$[\mathrm{Ar}]$$

Question 8

Which element has the highest first ionization energy?

Accepted Answer

Neon ($$\mathrm{Ne})$$

Question 9

Which of the following Lewis structures is correct for the carbonate ion, $$\mathrm{CO}_3$$^{2-}$$?

Accepted Answer

A structure with one double bond and two single bonds, with resonance among the three oxygens.

Question 10

Which molecular geometry is predicted for $$\mathrm{BF}_3$$ based on its Lewis structure?

Accepted Answer

Trigonal planar

Question 11

Which of the following molecules is polar?

Accepted Answer

$$\mathrm{NH}_3$$

Question 12

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity decreases down a group and increases across a period.

Question 13

Which of the following best explains why metals tend to lose electrons to form cations?

Accepted Answer

Metals have low ionization energies and low electronegativities.

Question 14

Which of the following is a resonance structure for the nitrate ion, $$\mathrm{NO}_3^-$$?

Accepted Answer

A structure with one N=O double bond and two N–O single bonds, with the double bond in different positions among the three oxygens.

Question 15

Which of the following best describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increased nuclear charge.

Question 16

A photon has a wavelength of $$400 nm. $$What is its energy in joules? ($$h = 6.626 	imes 10$$^{-34}$$ J·s, c = 3.00$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$4.97 	imes 10$$^{-19}$$ J

Question 17

Which of the following ions has the same electron configuration as argon ($$\mathrm{Ar}$$)?

Accepted Answer

$$\mathrm{K}^+$$

Question 18

Which of the following molecules has a bent molecular geometry?

Accepted Answer

$$\mathrm{H}_2O$$

Question 19

Which of the following best explains why $$\mathrm{F}_2 is $$nonpolar while $$\mathrm{HF} is $$polar?

Accepted Answer

$$\mathrm{F}_2 is $$composed of identical atoms, so the bond is nonpolar; $$\mathrm{HF}$$ has a large difference in electronegativity.

Study Guide for Exam 4 – Introductory Chemistry Concepts

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