Q: A sample of gas is collected in a laboratory experiment at 25°C and 1.00 atm. If the sample occupies 2.50 L, how many moles of gas are present? (Use the ideal gas law: $$PV = nRT$$, where $$R = 0.0821\ \text{L} \cdot \text{atm} \cdot \text{mol}^{-1} \cdot \text{K}^{-1})$$

$$n = \frac{(1.00)(2.50)}{0.0821 \times 298} = 0.102\ \text{mol}$$

Q: A reaction in a calorimeter absorbs 150 J of heat and does 50 J of work on the surroundings. What is the change in internal energy ($$\Delta U) $$for the system? (Use $$\Delta U = q + w)$$

$$\Delta U = 150 - 50 = 100\ \text{J}$$

Q: A student mixes 50.0 g of water at 25°C with 50.0 g of water at 75°C. What is the final temperature, assuming no heat loss to the environment? (Use $$q = m c \Delta T$$, $$c = 4.18\ \text{J/g} \cdot \text{°C})$$

Final temperature is $$50\ \text{°C}$$

Q: A mixture of gases contains 2.0 mol of O$$_2$$, 1.0 mol of N$$_2$$, and 1.0 mol of CO$$_2. If $$the total pressure is 2.0 atm, what is the partial pressure of O$$_2$$? (Use $$P_{O_2$} = X_{O_2$} \times P_{\text{total}})$$

$$P_{O_2$} = \frac{2.0}{4.0} \times 2.0 = 1.0\ \text{atm}$$

Question 1

A sample of gas is collected in a laboratory experiment at 25°C and 1.00 atm. If the sample occupies 2.50 L, how many moles of gas are present? (Use the ideal gas law: $$PV = nRT$$, where $$R = 0.0821\ 	ext{L} \cdot 	ext{atm} \cdot 	ext{mol}^{-1} \cdot 	ext{K}^{-1})$$

Accepted Answer

$$n = \frac{(1.00)(2.50)}{0.0821 	imes 298} = 0.102\ 	ext{mol}$$

Question 2

Which of the following best explains why real gases deviate from ideal behavior at high pressures?

Accepted Answer

Intermolecular forces between gas molecules become significant.

Question 3

A reaction in a calorimeter absorbs 150 J of heat and does 50 J of work on the surroundings. What is the change in internal energy ($$\Delta U) $$for the system? (Use $$\Delta U = q + w)$$

Accepted Answer

$$\Delta U = 150 - 50 = 100\ 	ext{J}$$

Question 4

Which periodic trend increases as you move from left to right across a period in the periodic table?

Accepted Answer

Ionization energy

Question 5

Which molecule below has a polar covalent bond?

Accepted Answer

HF

Question 6

What is the electron configuration for a neutral sodium atom ($$Z = 11$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 7

Which of the following best describes the shape of a molecule with 3 bonding pairs and 1 lone pair according to VSEPR theory?

Accepted Answer

Trigonal pyramidal

Question 8

Which intermolecular force is primarily responsible for the high boiling point of water?

Accepted Answer

Hydrogen bonding

Question 9

A student mixes 50.0 g of water at 25°C with 50.0 g of water at 75°C. What is the final temperature, assuming no heat loss to the environment? (Use $$q = m c \Delta T$$, $$c = 4.18\ 	ext{J/g} \cdot 	ext{°C})$$

Accepted Answer

Final temperature is $$50\ 	ext{°C}$$

Question 10

Which of the following statements about the Bohr model of the atom is correct?

Accepted Answer

Electrons occupy fixed orbits with quantized energies.

Question 11

Which element has the highest electron affinity?

Accepted Answer

Fluorine

Question 12

Which of the following molecules violates the octet rule?

Accepted Answer

BF$$_3$$

Question 13

Which of the following is a correct statement about resonance structures?

Accepted Answer

Resonance structures differ only in the arrangement of electrons.

Question 14

Which of the following best describes the relationship between temperature and kinetic energy of gas molecules?

Accepted Answer

As temperature increases, kinetic energy increases.

Question 15

Which of the following compounds is most likely to exhibit hydrogen bonding?

Accepted Answer

NH$$_3$$

Question 16

A mixture of gases contains 2.0 mol of O$$_2$$, 1.0 mol of N$$_2$$, and 1.0 mol of CO$$_2. If $$the total pressure is 2.0 atm, what is the partial pressure of O$$_2$$? (Use $$P_{O_2$} = X_{O_2$} 	imes P_{	ext{total}})$$

Accepted Answer

$$P_{O_2$} = \frac{2.0}{4.0} 	imes 2.0 = 1.0\ 	ext{atm}$$

Question 17

Which of the following best describes the effect of lone pairs on molecular geometry according to VSEPR theory?

Accepted Answer

Lone pairs decrease bond angles.

Question 18

Which of the following is a correct application of Hess's Law?

Accepted Answer

The enthalpy change of a reaction is independent of the pathway taken.

Question 19

Which of the following best describes the difference between ionic and covalent bonding?

Accepted Answer

Ionic bonding involves transferring electrons, covalent bonding involves sharing electrons.

Question 20

Which of the following statements about crystalline solids is correct?

Accepted Answer

Crystalline solids have a regular, repeating arrangement of atoms.

CHEM 1000: Chemical Structure – Course Syllabus and Study Guide

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