Question 1

Which of the following statements best describes the internal energy ($U$) of a system?

Accepted Answer

It is the sum of the potential and kinetic energies of the components of the system.

Question 2

Which of the following is an endothermic process?

Accepted Answer

Melting solid ice

Question 3

Calculate the value of $\Delta H$ for the reaction below, given the following enthalpies of formation:

$\mathrm{2H_2(g) + O_2(g) \rightarrow 2H_2O(l)}$

Given: $\Delta H_f^\circ [\mathrm{H_2O(l)}] = -286 \ \mathrm{kJ/mol}$

Accepted Answer

$-572 \ \mathrm{kJ}$

Question 4

A coffee-cup calorimeter contains 100.0 g of water at $25.0^\circ \mathrm{C}$. A 10.0 g sample of NaOH (molar mass = $40.0 \ \mathrm{g/mol}$) is dissolved in the water. The temperature rises to $37.0^\circ \mathrm{C}$. Assuming the specific heat of the solution is $4.18 \ \mathrm{J/g \cdot ^\circ C}$, calculate the enthalpy change per mole of NaOH dissolved.

Accepted Answer

$-50.2 \ \mathrm{kJ/mol}$

Question 5

Which of the following best explains why water has a much higher boiling point than methane ($\mathrm{CH_4}$)?

Accepted Answer

Water forms hydrogen bonds, which are much stronger than the London dispersion forces in methane.

Question 6

Given the reaction: $\mathrm{C_2H_4(g) + H_2(g) \rightarrow C_2H_6(g)}$, and the following bond energies:

$\mathrm{C=C}: 614 \ \mathrm{kJ/mol}$
$\mathrm{C-C}: 348 \ \mathrm{kJ/mol}$
$\mathrm{C-H}: 413 \ \mathrm{kJ/mol}$
$\mathrm{H-H}: 436 \ \mathrm{kJ/mol}$

Calculate $\Delta H$ for the reaction.

Accepted Answer

$-124 \ \mathrm{kJ}$

Question 7

Which of the following molecules has a trigonal planar geometry?

Accepted Answer

$\mathrm{BF_3}$

Question 8

A 2.00 L container holds $0.50$ mol of $\mathrm{N_2}$ gas at $27^\circ \mathrm{C}$. What is the pressure in the container? ($R = 0.0821 \ \mathrm{L \cdot atm \cdot mol^{-1} \cdot K^{-1}}$)

Accepted Answer

$6.1 \ \mathrm{atm}$

Question 9

Which of the following statements about the hybridization of the central atom in $\mathrm{CO_2}$ is correct?

Accepted Answer

The carbon atom is $sp$ hybridized.

Question 10

Which of the following best describes the shape of $\mathrm{SF_6}$ according to VSEPR theory?

Accepted Answer

Octahedral

Question 11

A sample of $\mathrm{NH_3}$ gas occupies $5.00 \ \mathrm{L}$ at $27^\circ \mathrm{C}$ and $1.00 \ \mathrm{atm}$. What will be its volume at $-73^\circ \mathrm{C}$ and $1.00 \ \mathrm{atm}$?

Accepted Answer

$3.33 \ \mathrm{L}$

Question 12

Which of the following molecules is expected to have the lowest boiling point?

Accepted Answer

$\mathrm{CH_4}$

Question 13

Which of the following is the best Lewis structure for $\mathrm{OCl_2}$?

Accepted Answer

O in the center with two single bonds to Cl, and two lone pairs on O, each Cl with three lone pairs.

Question 14

Which of the following is a correct statement about the relationship between $q$, $w$, and $\Delta U$ in the first law of thermodynamics?

Accepted Answer

$\Delta U = q + w$

Question 15

Which of the following molecules has a bond angle closest to $109.5^\circ$?

Accepted Answer

$\mathrm{CH_4}$

Question 16

Which of the following is a correct statement about the enthalpy change ($\Delta H$) for a chemical reaction?

Accepted Answer

It is the heat absorbed or released at constant pressure.

Question 17

Which of the following molecules is nonpolar?

Accepted Answer

$\mathrm{CO_2}$

Question 18

Which of the following is the correct order of decreasing F–C–F bond angle in the compounds below?

I. $\mathrm{BF_2Cl}$
II. $\mathrm{CF_2Cl_2}$
III. $\mathrm{SiF_2Cl_2}$

Accepted Answer

I > II > III

Question 19

Which of the following molecules is expected to have the strongest London dispersion forces?

Accepted Answer

$\mathrm{C_6H_{14}}$

Question 20

Which of the following is the correct electron configuration for $\mathrm{Fe^{2+}}$?

Accepted Answer

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

General Chemistry Practice Exam Study Guide: Thermochemistry, Bonding, Gases, and Molecular Structure

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