Comprehensive Study Notes: Solutions, Acids & Bases, and Hydrocarbons

Solutions and Their Properties

Definition and Components of a Solution

A solution is a homogeneous mixture composed of two or more substances. The substance present in the largest amount is the solvent, and the substance(s) dissolved are the solute(s).

• Solvent: The medium in which the solute is dissolved (e.g., water in saltwater).

• Solute: The substance dissolved in the solvent (e.g., NaCl in saltwater).

• Homogeneous: Uniform composition throughout.

• Examples: Sugar dissolved in water, air (a mixture of gases).

Concentration Units and Calculations

Concentration expresses the amount of solute in a given amount of solution or solvent. Common units include:

• Percent by mass (% m/m): $\%\ (m/m) = \frac{\text{mass of solute (g)}}{\text{mass of solution (g)}} \times 100$

• Percent by volume (% v/v): $\%\ (v/v) = \frac{\text{volume of solute (mL)}}{\text{volume of solution (mL)}} \times 100$

• Percent mass/volume (% m/v): $\%\ (m/v) = \frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}} \times 100$

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

These units can be used as conversion factors in calculations.

Dilution of Solutions

Dilution involves adding solvent to decrease the concentration of a solution. The relationship is given by:

• $M_1V_1 = M_2V_2$

• Where $M_1$ and $V_1$ are the initial molarity and volume, and $M_2$ and $V_2$ are the final molarity and volume.

Types of Mixtures: Solutions, Colloids, and Suspensions

Mixtures can be classified based on particle size and behavior:

Type	Particle Size	Appearance	Separation
Solution	< 1 nm	Clear	Not separated by filtration
Colloid	1-1000 nm	Cloudy	Not separated by filtration, but by ultrafiltration
Suspension	> 1000 nm	Cloudy, settles	Separated by filtration or settling

Osmosis, Diffusion, and Tonicity

• Diffusion: Movement of particles from high to low concentration.

• Osmosis: Diffusion of water across a semipermeable membrane.

• Osmotic Pressure: Pressure required to stop osmosis.

Solution Type	Relative Solute Concentration	Effect on Red Blood Cells
Isotonic	Equal to cell	No net water movement
Hypotonic	Lower than cell	Cell swells (hemolysis)
Hypertonic	Higher than cell	Cell shrinks (crenation)

Solubility and "Like Dissolves Like"

• Solubility: Ability of a substance to dissolve in a solvent.

• Polarity: Polar solutes dissolve in polar solvents (e.g., NaCl in water); nonpolar solutes dissolve in nonpolar solvents (e.g., oil in hexane).

• Intermolecular Forces: Hydrogen bonding, dipole-dipole, and London dispersion forces affect solubility.

Example: CH3F (polar) is more soluble in water (polar) than CCl4 (nonpolar).

Electrolytes and Nonelectrolytes

• Strong Electrolyte: Completely dissociates in water (e.g., NaCl).

• Weak Electrolyte: Partially dissociates (e.g., acetic acid).

• Nonelectrolyte: Does not dissociate (e.g., sugar).

Dissociation of Salts and Ion Concentrations

• Soluble salts dissociate into ions in water.

• Concentration of ions can be expressed in molarity (M) or milliequivalents per liter (mEq/L).

• Example: NaCl $\rightarrow$ Na+ + Cl-

Acids, Bases, and Buffers

Acids, Bases, and pH

• Acid: Substance that donates H+ ions in solution.

• Base: Substance that accepts H+ ions or donates OH-.

• pH: Measure of acidity/basicity: $pH = -\log_{10}[H_3O^+]$

• pOH: $pOH = -\log_{10}[OH^-]$

• Relationship: $pH + pOH = 14$

pH Range	Solution Type
< 7	Acidic
= 7	Neutral
> 7	Basic

Conjugate Acid-Base Pairs

• When an acid donates a proton, it forms its conjugate base.

• When a base accepts a proton, it forms its conjugate acid.

• Example: $NH_3 + H_2O \rightleftharpoons NH_4^+ + OH^-$

Strong vs. Weak Acids

• Strong Acid: Completely ionizes in water (e.g., HCl).

• Weak Acid: Partially ionizes (e.g., CH3COOH).

• Relative concentrations: Strong acids produce more H+ ions than weak acids at the same concentration.

Neutralization and Titration

• Neutralization: Acid reacts with base to form water and a salt.

• Titration: Analytical method to determine concentration by reacting with a standard solution.

• Calculation: Use molarity and volume to find moles: $M_1V_1 = M_2V_2$

Buffers

• Buffer: Solution that resists changes in pH upon addition of acid or base.

• Composed of a weak acid and its conjugate base (or weak base and conjugate acid).

• Example: $H_2PO_4^- / HPO_4^{2-}$ buffer system.

• Acid added: $H_2PO_4^- + H^+ \rightarrow H_3PO_4$

• Base added: $H_2PO_4^- + OH^- \rightarrow HPO_4^{2-} + H_2O$

Preparation of Solutions

Preparation Steps and Calculations

• To prepare a specific concentration, calculate the required mass or volume of solute and solvent.

• Example a: To prepare 250 mL of 0.45% (m/v) NaCl: $0.45\% = \frac{\text{g NaCl}}{250\ \text{mL}} \times 100$

• Example b: To prepare 450 mL of 50 mM NaCl: $\text{moles} = 0.050\ \text{mol/L} \times 0.450\ \text{L}$

• Example c: Diluting 15.0 mL of solution with 45.0 mL water: Use $M_1V_1 = M_2V_2$

• Example d: If you have 25.0 g NaCl, how many mL of 0.45% (m/v) solution can be made? $\text{Volume} = \frac{25.0\ \text{g}}{0.45\ \text{g/mL}} \times 100$

Organic Chemistry: Hydrocarbons

Alkanes, Alkenes, Alkynes: Names and Structures

• Alkanes: Saturated hydrocarbons (single bonds only).

• Alkenes: Unsaturated hydrocarbons (at least one double bond).

• Alkynes: Unsaturated hydrocarbons (at least one triple bond).

• Can be straight-chain, branched, or cyclic.

• Structures can be shown as condensed, structural, or skeletal (line-angle) formulas.

Cis-Trans Isomerism in Alkenes

• Cis Isomer: Similar groups on the same side of the double bond.

• Trans Isomer: Similar groups on opposite sides of the double bond.

Saturated vs. Unsaturated Hydrocarbons

• Saturated: Only single bonds (alkanes).

• Unsaturated: Contains double or triple bonds (alkenes, alkynes).

Reactions of Hydrocarbons

• Combustion: Hydrocarbon + O2 → CO2 + H2O

• Hydrogenation: Alkene + H2 → Alkane (addition of hydrogen)

• Hydration: Alkene + H2O → Alcohol

Example: CH3CH2CH2COOH + O2 → CO2 + H2O (combustion)

Aromatic Compounds

• Benzene: C6H6, planar ring structure, delocalized electrons.

• Derivatives: Compounds with benzene ring and substituents (e.g., toluene, phenol).

• Properties: Stability due to resonance, undergo substitution reactions.

Additional info:

• Lewis structures and intermolecular forces are important for predicting solubility and reactivity.

• Milliequivalents (mEq) are used in clinical chemistry to express ion concentrations: $\text{mEq/L} = \text{mmol/L} \times |\text{charge}|$