Q: A sample of gas occupies 2.50 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 250 K, what is the new volume of the gas? (Assume ideal gas behavior.)

$$V_2$$ = $$V_1$$ \times \frac{$$P_1$$}{$$P_2$$} \times \frac{$$T_2$$}{$$T_1$$} = 2.50\,\mathrm{L} \times \frac{1.00}{2.00} \times \frac{250}{300} = 1.04\,\mathrm{L}$$

Question 1

Which of the following best explains why ionic compounds generally have higher melting points than covalent compounds?

Accepted Answer

Ionic compounds consist of ions held together by strong electrostatic forces, requiring more energy to separate them.

Question 2

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 250 K, what is the new volume of the gas? (Assume ideal gas behavior.)

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \frac{$$P_1$$}{$$P_2$$} 	imes \frac{$$T_2$$}{$$T_1$$} = 2.50\,\mathrm{L} 	imes \frac{1.00}{2.00} 	imes \frac{250}{300} = 1.04\,\mathrm{L}$$

Question 3

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have the same number of valence electrons.

Question 4

Which of the following best describes the process of assigning oxidation numbers in the compound $$\mathrm{H_2SO_4}$$?

Accepted Answer

Assign hydrogen as $$+1$$, oxygen as $$-2$$, and solve for sulfur.

Question 5

A student mixes 50.0 mL of 1.00 M $$\mathrm{HCl}$$ with 50.0 mL of 1.00 M $$\mathrm{NaOH}. $$What is the final pH of the solution?

Accepted Answer

pH = 7, because the acid and base completely neutralize each other.

Question 6

Which of the following is the correct electron configuration for a ground-state phosphorus atom ($$Z=15$$)?

Accepted Answer

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

Question 7

Which of the following molecules is polar?

Accepted Answer

$$\mathrm{NH_3$}$$

Question 8

Which of the following best describes the difference between sigma ($$\sigma) $$and pi ($$\pi) $$bonds?

Accepted Answer

$$\sigma$$ bonds result from end-to-end overlap, while $$\pi$$ bonds result from side-to-side overlap.

Question 9

A reaction has $$\Delta H = -100\ \mathrm{kJ}$$ and $$\Delta S = -200\ \mathrm{J/K}. At $$what temperature (in K) does the reaction change from spontaneous to nonspontaneous? ($$\Delta G = \Delta H - T\Delta S)$$

Accepted Answer

$$T = \frac{\Delta H}{\Delta S} = \frac{-100\,000}{-200} = 500\ \mathrm{K}$$

Question 10

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

Accepted Answer

Water molecules form hydrogen bonds, which are stronger than the London dispersion forces in methane.

Question 11

Which of the following is the correct balanced equation for the combustion of propane ($$\mathrm{C_3H_8}$$)?

Accepted Answer

$$\mathrm{C_3H_8} + 5\mathrm{O_2$} \rightarrow 3\mathrm{CO_2$} + 4\mathrm{H_2O}$$

Question 12

Which of the following statements about hybridization is correct?

Accepted Answer

A carbon atom with four single bonds is $$sp^3$$ hybridized.

Question 13

Which of the following best describes the effect of increasing temperature on the solubility of a gas in water?

Accepted Answer

The solubility of a gas in water decreases as temperature increases.

Question 14

Which of the following is the correct Lewis structure for $$\mathrm{CO_2$}$$?

Accepted Answer

O=C=O, with each O atom having two lone pairs.

Question 15

Which of the following best describes the trend in atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 16

A solution is prepared by dissolving 10.0 g of $$\mathrm{NaCl} in $$enough water to make 500.0 mL of solution. What is the molarity of the solution? ($$\mathrm{NaCl}$$ molar mass = 58.44 g/mol)

Accepted Answer

$$\mathrm{M} = \frac{10.0\,g}{58.44\,g/mol} \div 0.500\,L = 0.342\,M$$

Question 17

Which of the following best explains why ice floats on water?

Accepted Answer

Ice is less dense than liquid water due to the open hexagonal structure formed by hydrogen bonding.

Question 18

Which of the following is the correct expression for the equilibrium constant $$K_c$$ for the reaction $$\mathrm{N_2$}(g) + 3\mathrm{H_2$}(g) \rightleftharpoons 2\mathrm{NH_3$}(g)$$?

Accepted Answer

$$K_c = \frac{[\mathrm{NH_3$}]^2}{[\mathrm{N_2$}][\mathrm{H_2$}]^3}$$

Question 19

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy, increasing the reaction rate without being consumed.

General Chemistry Course Learning Objectives and Key Topics

Guida di studio - Domande di pratica

Study guide - Flashcard