Q: Calculate the energy of a photon with a wavelength of $400\ \mathrm{nm}$. ($c = 3.00 \times 10^8\ \mathrm{m/s}$, $h = 6.626 \times 10^{-34}\ \mathrm{J\cdot s}$)

$4.97 \times 10^{-19}\ \mathrm{J}$

Question 1

A sample of ethanol has a mass of 39.5 g and occupies a volume of 50.0 mL. What is the density of ethanol in $\mathrm{g/mL}$?

Accepted Answer

$0.79\ \mathrm{g/mL}$

Question 2

Which of the following elements has the highest first ionization energy?

Accepted Answer

Neon (Ne)

Question 3

A neutral atom of chlorine has 17 protons, 18 neutrons, and 17 electrons. What is the mass number of this atom?

Accepted Answer

$35$

Question 4

Which of the following ions is isoelectronic with argon ($\mathrm{Ar}$)?

Accepted Answer

$\mathrm{K^+}$

Question 5

What is the condensed electron configuration for iron ($\mathrm{Fe}$, atomic number 26)?

Accepted Answer

$[\mathrm{Ar}]\ 4s^2\ 3d^6$

Question 6

Which molecule has a trigonal planar molecular geometry according to VSEPR theory?

Accepted Answer

$\mathrm{BF_3}$

Question 7

Calculate the energy of a photon with a wavelength of $400\ \mathrm{nm}$. ($c = 3.00 	imes 10^8\ \mathrm{m/s}$, $h = 6.626 	imes 10^{-34}\ \mathrm{J\cdot s}$)

Accepted Answer

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

Question 8

Which of the following compounds is ionic?

Accepted Answer

$\mathrm{NaCl}$

Question 9

What is the formal charge on the central nitrogen atom in $\mathrm{NO_3^-}$ (nitrate ion) in its best Lewis structure?

Accepted Answer

$0$

Question 10

Which of the following statements about lattice energy is correct?

Accepted Answer

Lattice energy increases as the charges on the ions increase and the ionic radii decrease.

Question 11

Which element has the highest electronegativity?

Accepted Answer

Fluorine

Question 12

How many unpaired electrons are present in a ground-state atom of oxygen ($\mathrm{O}$)?

Accepted Answer

2

Question 13

Which of the following molecules is polar?

Accepted Answer

$\mathrm{NH_3}$

Question 14

What is the bond angle in a molecule with $sp^3$ hybridization and no lone pairs on the central atom?

Accepted Answer

$109.5^\circ$

Question 15

Which rule states that electrons fill orbitals of lowest energy first?

Accepted Answer

Aufbau principle

Question 16

Which of the following is a correct Lewis structure for $\mathrm{CO_2}$?

Accepted Answer

O=C=O, with each O having two lone pairs

Question 17

Which of the following is a resonance structure for the nitrate ion ($\mathrm{NO_3^-}$)?

Accepted Answer

One N-O double bond and two N-O single bonds, with the double bond rotating among the three oxygens

Question 18

Which of the following statements about sigma ($\sigma$) and pi ($\pi$) bonds is correct?

Accepted Answer

A double bond consists of one $\sigma$ bond and one $\pi$ bond.

Question 19

Which of the following pairs of atoms/ions are isoelectronic?

Accepted Answer

$\mathrm{O^{2-}}$ and $\mathrm{Ne}$

Question 20

Which of the following best describes the molecular orbital (MO) theory for $\mathrm{O_2}$?

Accepted Answer

$\mathrm{O_2}$ has two unpaired electrons in its antibonding $\pi^*$ orbitals, making it paramagnetic.

General Chemistry Core Concepts: Atomic Structure, Bonding, and Molecular Geometry

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