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 \u003e II \u003e 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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