Q: Which of the following is the correct formula for calculating the number of moles from the number of molecules?

$\text{moles} = \dfrac{\text{number of molecules}}{6.02 \times 10^{23}}$

Question 1

Which of the following best describes the Bronsted-Lowry definition of an acid?

Accepted Answer

A substance that donates a proton (H$^+$) to another substance.

Question 2

A student mixes 0.50 mol of HCl with 1.0 L of water. What is the concentration of H$^+$ ions in the solution?

Accepted Answer

$[H^+] = 0.50\ \mathrm{M}$

Question 3

Which of the following reactions is an example of a decomposition reaction?

Accepted Answer

$2KClO_3 \rightarrow 2KCl + 3O_2$

Question 4

Given the reaction: $2Na + Cl_2 \rightarrow 2NaCl$, how many grams of NaCl are produced from 46.0 g of Na? (Molar mass Na = 23.0 g/mol, NaCl = 58.5 g/mol)

Accepted Answer

117 g

Question 5

Which of the following statements about exothermic and endothermic reactions is correct?

Accepted Answer

Exothermic reactions release energy to the surroundings.

Question 6

A buffer solution is prepared by mixing acetic acid ($CH_3COOH$) and sodium acetate ($CH_3COONa$). Which pair of molecules is responsible for the buffer action?

Accepted Answer

$CH_3COOH$ and $CH_3COONa$

Question 7

Calculate the pH of a solution with $[H^+] = 1.0 	imes 10^{-5}\ \mathrm{M}$.

Accepted Answer

$pH = 5$

Question 8

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid ($HCl$)

Question 9

A reaction has $K_{eq} = 1.0 	imes 10^{-7}$. What does this indicate about the equilibrium position?

Accepted Answer

The reactants are favored at equilibrium.

Question 10

Which of the following best describes Le Chatelier's Principle?

Accepted Answer

If a system at equilibrium is disturbed, the system will shift to minimize the disturbance.

Question 11

Which of the following is the correct formula for calculating the number of moles from the number of molecules?

Accepted Answer

$	ext{moles} = \dfrac{	ext{number of molecules}}{6.02 	imes 10^{23}}$

Question 12

Which of the following is the correct formula for a hydrocarbon with 5 carbon atoms and only single bonds?

Accepted Answer

$C_5H_{12}$

Question 13

Which of the following is the correct expression for the acid dissociation constant ($K_a$)?

Accepted Answer

$K_a = \dfrac{[A^-][H^+]}{[HA]}$

Question 14

A solution is prepared by mixing 100 mL of 0.2 M NaOH with 200 mL of 0.1 M HCl. What is the final concentration of NaCl produced?

Accepted Answer

$0.067\ \mathrm{M}$

Question 15

Which of the following is the correct formula for calculating the pH of a solution?

Accepted Answer

$pH = -\log [H^+]$

Question 16

Which of the following is a product of the neutralization reaction between H$_2$SO$_4$ and NaOH?

Accepted Answer

Na$_2$SO$_4$

Question 17

Which of the following is the correct condensed structural formula for butane?

Accepted Answer

$CH_3CH_2CH_2CH_3$

Question 18

Which of the following best describes the geometry and bond angles of methane ($CH_4$)?

Accepted Answer

Tetrahedral, 109.5$^\circ$

Question 19

Which of the following is the correct formula for a dilution problem?

Accepted Answer

$M_1V_1 = M_2V_2$

GOB Chemistry Exam 2 Study Guide: Chemical Reactions, Acids & Bases, and Hydrocarbons

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