Q: Which of the following is the correct formula to calculate the mass percent of an element X in a compound?

$$\frac{\text{mass of element X in 1 mol of compound}}{\text{mass of 1 mol of the compound}} \times 100\%$$

Q: A sample contains 24.0 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.0 g/mol, Avogadro's number = $$6.022 \times 10$$^{23}$$)

$$1.20 \times 10$$^{24}$$ atoms

Question 1

Which hybridization scheme is associated with a molecule that has a linear electron geometry according to VSEPR theory?

Accepted Answer

$$sp$$

Question 2

What is the bond order of the $$\mathrm{H_2$}$$ molecule according to molecular orbital theory?

Accepted Answer

$$1$$

Question 3

Which of the following statements best explains why $$\mathrm{O_2$} is $$paramagnetic, even though its Lewis structure predicts it should be diamagnetic?

Accepted Answer

Because $$\mathrm{O_2$}$$ has unpaired electrons in its antibonding $$\pi^*$$ molecular orbitals.

Question 4

A molecule has five electron groups around its central atom. What is the expected hybridization of the central atom?

Accepted Answer

$$sp^3d$

Question 5

Which of the following best describes the difference between a $$\sigma$$ bond and a $$\pi$$ bond?

Accepted Answer

$$\sigma$$ bonds result from end-to-end overlap along the internuclear axis, while $$\pi$$ bonds result from side-to-side overlap of parallel p orbitals.

Question 6

Given the following molecular orbital diagram for $$\mathrm{He_2$}$$, what is the bond order and does the molecule exist?

Accepted Answer

Bond order = 0; molecule does not exist.

Question 7

Which of the following molecules is predicted to be nonpolar based on its molecular geometry and bond polarity?

Accepted Answer

Carbon dioxide ($$\mathrm{CO_2$})$$

Question 8

What is the hybridization of the central atom in $$\mathrm{SF_6$}$$, and what is the expected bond angle?

Accepted Answer

$$sp^3d^2$; 90^\circ$$

Question 9

Which of the following is the correct formula to calculate the mass percent of an element X in a compound?

Accepted Answer

$$\frac{	ext{mass of element X in 1 mol of compound}}{	ext{mass of 1 mol of the compound}} 	imes 100\%$$

Question 10

A sample contains 24.0 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.0 g/mol, Avogadro's number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$1.20 	imes 10$$^{24}$$ atoms

Question 11

Which of the following best describes the molecular orbital formed by the constructive interference of two 1s atomic orbitals?

Accepted Answer

A bonding $$\sigma_{1s}$$ orbital with electron density between nuclei

Question 12

Which of the following molecules has a trigonal bipyramidal electron geometry and what is its hybridization?

Accepted Answer

$$\mathrm{$$PCl_5$$}$$; $$sp^3d$

Question 13

If a molecule has three electron groups and one lone pair around the central atom, what is its molecular geometry and approximate bond angle?

Accepted Answer

Bent; \u003c120°

Question 14

Which of the following is true about the bond order and stability of a molecule with equal numbers of electrons in bonding and antibonding molecular orbitals?

Accepted Answer

Bond order is 0; molecule is not stable.

Question 15

Which of the following best explains why rotation around a double bond is restricted?

Accepted Answer

Because the $$\pi$$ bond, formed by side-to-side overlap of p orbitals, would be broken upon rotation.

Question 16

A molecule has a net dipole moment. Which of the following must be true?

Accepted Answer

The molecule must have polar bonds and a non-symmetrical geometry.

Question 17

Which of the following is the correct formula for calculating the number of molecules in a given mass of a compound?

Accepted Answer

$$	ext{Number of molecules} = \frac{	ext{mass}}{	ext{molar mass}} 	imes 6.022 	imes 10$$^{23}$$

Bonding Theories, Hybridization, Molecular Orbitals, and Chemical Quantities: General Chemistry Study Guide

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