GOB Chemistry Exam Study Guide: Acids, Bases, Solutions, Organic Nomenclature, and Chemical Quantities

Acids and Bases

Bronsted-Lowry Acid-Base Theory

The Bronsted-Lowry theory defines acids as proton (H+) donors and bases as proton acceptors. Conjugate acid-base pairs differ by one proton.

• Acid: Donates H+ (e.g., HSO4-)

• Base: Accepts H+ (e.g., OH-)

• Conjugate Acid: Formed when a base gains a proton

• Conjugate Base: Formed when an acid loses a proton

Example: In the reaction HSO4- + OH- → SO42- + H2O, HSO4- is the acid, OH- is the base, SO42- is the conjugate base, and H2O is the conjugate acid.

Acid Strength and pH

Acid strength is determined by the degree of ionization in water. Strong acids ionize completely, while weak acids only partially ionize.

• Strong Acids: HCl, HNO3, H2SO4

• Strong Bases: NaOH, KOH

• pH Calculation: $pH = -\log[H_3O^+]$

• pOH Calculation: $pOH = -\log[OH^-]$

• Relationship: $pH + pOH = 14$

Example Table:

[H3O+]	[OH-]	pH	Acidic/Basic
5.6 × 10-7	1.8 × 10-8	6.25	Acidic
1.2 × 10-10	8.2 × 10-5	9.92	Basic

Le Châtelier's Principle

Shifts in Chemical Equilibrium

Le Châtelier's Principle states that if a system at equilibrium is disturbed, the system will shift to counteract the disturbance and restore equilibrium.

• Adding Reactant: Shifts equilibrium toward products

• Removing Reactant: Shifts equilibrium toward reactants

• Adding Product: Shifts equilibrium toward reactants

• Removing Product: Shifts equilibrium toward products

Example: For CH3COOH (aq) + NH3 (aq) ⇌ CH3COO- (aq) + NH4+ (aq), adding NH3 shifts toward products.

Electrolytes and Solubility

Types of Electrolytes

Electrolytes are substances that conduct electricity when dissolved in water.

• Strong Electrolytes: Completely dissociate (e.g., NaCl)

• Weak Electrolytes: Partially dissociate (e.g., CH3COOH)

• Nonelectrolytes: Do not dissociate (e.g., sugar)

Solubility Rules for Ionic Compounds

Solubility rules help predict whether an ionic compound will dissolve in water.

Positive Ion	Negative Ion	Solubility
Na+, K+, NH4+	Any	Soluble
Any	NO3-, CH3COO-	Soluble
Any	SO42-	Soluble except with Ba2+, Pb2+, Ca2+
Any	Cl-, Br-, I-	Soluble except with Ag+, Pb2+

Example: NaNO3 is soluble; PbBr2 is insoluble.

Properties of Solutions

Concentration Calculations

Concentration is commonly expressed as molarity (M), which is moles of solute per liter of solution.

• Molarity Formula: $M = \frac{\text{moles of solute}}{\text{liters of solution}}$

• Dilution Formula: $C_1V_1 = C_2V_2$

Example: To prepare 375 mL of 1.8% (w/v) solution from 6.2% (w/v) stock, use $V_1 = \frac{C_2V_2}{C_1}$.

Osmosis and Tonicity

Osmosis is the movement of water across a semipermeable membrane. Tonicity describes the effect of a solution on cell volume.

• Hypotonic: Lower solute concentration; cells swell (hemolysis)

• Hypertonic: Higher solute concentration; cells shrink (crenation)

• Isotonic: Equal solute concentration; no change

Example: 0.9% NaCl and 5% glucose are isotonic to human cells.

Gas Laws

Relationships Between Pressure, Volume, and Temperature

Gas laws describe the behavior of gases under varying conditions.

• Boyle's Law: $P_1V_1 = P_2V_2$ (at constant T)

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant P)

• Combined Gas Law: $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$

• Ideal Gas Law: $PV = nRT$

• Molar Volume at STP: 1 mol = 22.4 L at 1 atm and 0°C

Example: Calculate the volume of 3.08 g H2O vapor at STP using molar mass and molar volume.

Chemical Reactions and Equations

Balancing Chemical Equations

Balanced equations have equal numbers of each atom on both sides. Coefficients are used to balance equations.

• Example: $C_9H_{20}(l) + 14O_2(g) \rightarrow 9CO_2(g) + 10H_2O(g)$

Types of Reactions

• Acid-Base Neutralization: Acid + Base → Salt + Water

• Acid-Metal Reaction: Acid + Metal → Salt + Hydrogen Gas

Example: $Ba(OH)_2(aq) + 2HCl(aq) \rightarrow BaCl_2(aq) + 2H_2O(l)$

Organic Chemistry: Nomenclature and Isomerism

IUPAC Naming of Alkanes

Alkanes are named based on the longest carbon chain and the position of substituents.

• Parent Chain: Longest continuous chain (e.g., nonane = 9 carbons)

• Substituents: Groups attached to the main chain (e.g., methyl, bromo)

• Numbering: Assign lowest possible numbers to substituents

Example: 6-bromo-2,5-dimethylnonane

Structural Isomers

Structural isomers have the same molecular formula but different connectivity of atoms.

• Example: C4H10: n-butane and isobutane

Periodic Table and Atomic Mass

Atomic Mass Calculations

Atomic mass is the weighted average of the masses of isotopes of an element. Molar mass is used to convert between grams and moles.

• Example: Molar mass of BaCO3: $137.33 + 12.01 + 3(16.00) = 197.34$ g/mol

Useful Equations and Constants

• $C_1V_1 = C_2V_2$ (Dilution)

• $PV = nRT$ (Ideal Gas Law)

• $pH = -\log[H_3O^+]$

• $pOH = -\log[OH^-]$

• $pH + pOH = 14$

• 1 mol gas at STP = 22.4 L

• 1 atm = 760 mmHg

Additional info:

• Periodic Table included for reference to atomic numbers and symbols.

• Some calculations and examples inferred for completeness.