Question 1

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

Accepted Answer

It is the sum of the potential and kinetic energies of the system's molecules.

Question 2

Which of the following is an endothermic process?

Accepted Answer

Melting solid ice

Question 3

Calculate $$\Delta H$$ for the reaction below, given $$\Delta H_f$$ values: $$\Delta H_f(\mathrm{CO_2$}) = -393.5\ \mathrm{kJ/mol}$$, $$\Delta H_f(\mathrm{H_2O}) = -285.8\ \mathrm{kJ/mol}$$, $$\Delta H_f(\mathrm{CH_4$}) = -74.8\ \mathrm{kJ/mol}$$.

$$\mathrm{CH_4$}(g) + 2\mathrm{O_2$}(g) \rightarrow \mathrm{CO_2$}(g) + 2\mathrm{H_2O}(l)$$

Accepted Answer

$$-890.1\ \mathrm{kJ}$$

Question 4

A coffee-cup calorimeter contains 100.0 g of water at $$22.0^\circ\mathrm{C}. $$When 6.00 g of ammonium nitrate ($$\mathrm{NH_4NO_3}) is $$dissolved, the temperature drops to $$16.7^\circ\mathrm{C}. $$What is the enthalpy change ($$q) $$for the dissolution process? (Specific heat of water $$= 4.18\ \mathrm{J/g\cdot K})$$

Accepted Answer

$$+2.21\ \mathrm{kJ}$$

Question 5

Which of the following statements about bond enthalpy is correct?

Accepted Answer

Breaking bonds requires energy, while forming bonds releases energy.

Question 6

Given the reaction: $$2\mathrm{H_2$}(g) + \mathrm{O_2$}(g) \rightarrow 2\mathrm{H_2O}(l)$$, and the standard enthalpy of formation $$\Delta H_f(\mathrm{H_2O}) = -285.8\ \mathrm{kJ/mol}$$, what is the enthalpy change for the reaction?

Accepted Answer

$$-571.6\ \mathrm{kJ}$$

Question 7

A sample of gas at $$1.00\ \mathrm{atm}$$ and $$273\ \mathrm{K}$$ occupies $$22.4\ \mathrm{L}. $$What is the mass of $$\mathrm{O_2$}$$ gas in the sample?

Accepted Answer

$$32.0\ \mathrm{g}$$

Question 8

Which of the following molecules has the highest boiling point?

Accepted Answer

$$\mathrm{H_2O}$$

Question 9

What is the hybridization of the central carbon atom in $$\mathrm{CO_2$}$$?

Accepted Answer

$$sp$$

Question 10

Which of the following best explains why $$\mathrm{H_2O}$$ has a higher boiling point than $$\mathrm{H_2S}$$?

Accepted Answer

Hydrogen bonding in $$\mathrm{H_2O} is $$stronger than in $$\mathrm{H_2S}.$$

Question 11

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

Accepted Answer

O with two single bonds to Cl, each Cl with three lone pairs, O with two lone pairs

Question 12

Which of the following molecules is nonpolar?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 13

What is the electron geometry around the central atom in $$\mathrm{BF_3$}$$?

Accepted Answer

Trigonal planar

Question 14

Which of the following statements about London dispersion forces is correct?

Accepted Answer

They are present in all molecules, but are the only intermolecular force in nonpolar molecules.

Question 15

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

Accepted Answer

Octahedral

Question 16

A 2.00 g sample of $$\mathrm{NaOH} is $$dissolved in water in a coffee-cup calorimeter. The temperature of the solution increases from $$25.0^\circ\mathrm{C} to$$ $$27.5^\circ\mathrm{C}. If $$the specific heat capacity of the solution is $$4.18\ \mathrm{J/g\cdot K}$$ and the total mass is $$100.0\ \mathrm{g}$$, what is the heat released?

Accepted Answer

$$104.5\ \mathrm{J}$$

Question 17

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

Accepted Answer

$$\mathrm{CH_4$}$$

Question 18

Which of the following is true for a process at constant volume?

Accepted Answer

$$q = \Delta E$$ and $$\Delta H = \Delta E$$

Question 19

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

Accepted Answer

$$\mathrm{CH_4$}$$

Question 20

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

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

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

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