Solutions

Definition and Components

A solution is a homogeneous mixture of two or more substances. It forms when there is sufficient attraction between the solute and solvent molecules. The solvent is present in a much larger amount, while the solute is present in a smaller amount.

• Solute: The substance present in lesser amount.

• Solvent: The substance present in greater amount.

• Example: Salt dissolved in water forms a solution.

Types of Solutes and Solvents

Solutes and solvents can be solids, liquids, or gases, resulting in various types of solutions.

Formation of Solutions: "Like Dissolves Like"

Solutions form when the solute and solvent have similar polarities. Polar solutes dissolve in polar solvents, and nonpolar solutes dissolve in nonpolar solvents.

Electrolytes and Nonelectrolytes

Electrolytes in the Body

Electrolytes are substances that dissociate into ions in solution and conduct electricity. They are essential for proper cell and organ function. Common electrolytes include sodium, potassium, chloride, and bicarbonate.

Classification of Solutes in Aqueous Solutions

Solubility

Definition and Factors Affecting Solubility

Solubility is the maximum amount of solute that dissolves in a specific amount of solvent. It is temperature sensitive and is usually expressed as grams of solute per 100 grams of solvent.

• Unsaturated solution: Contains less solute than the maximum amount.

• Saturated solution: Contains the maximum amount of solute.

Effect of Temperature on Solubility

Solubility of most solids increases as temperature increases, while solubility of gases decreases as temperature increases.

Solubility and Pressure (Henry's Law)

Henry's law states that the solubility of a gas in a liquid is directly related to the pressure of that gas above the liquid. At higher pressures, more gas molecules dissolve in the liquid.

Soluble and Insoluble Ionic Compounds

Not all ionic compounds are soluble in water. Solubility rules help predict which compounds will dissolve.

Solution Concentration

Units of Concentration

The concentration of a solution is expressed in several units:

• Mass percent (m/m)

• Volume percent (v/v)

• Mass/volume percent (m/v)

• Molarity (moles solute/liters solution)

Dilution

Principles of Dilution

In a dilution, water is added, increasing the volume and decreasing the concentration, but the mass of solute remains the same. The relationship is given by:

Properties of Solutions

Isotonic Solutions

A 0.9% NaCl solution is isotonic with the solute concentration of blood cells, meaning it has the same osmotic pressure as blood.

Suspensions

Suspensions are heterogeneous mixtures with large particles that settle out and can be filtered. Examples include blood platelets and muddy water.

Comparison of Solutions, Colloids, and Suspensions

Osmotic Pressure

Osmotic pressure is the pressure that prevents the flow of additional water into a more concentrated solution. It increases with the number of dissolved particles.

Reverse Osmosis

Reverse osmosis is a purification process where pressure greater than the osmotic pressure is applied to force water through a membrane, leaving solute molecules and ions behind.

Concept Map: Solutions

Acids and Bases

Arrhenius Acids

Arrhenius acids produce hydrogen ions (H+) when dissolved in water. They are electrolytes, have a sour taste, turn blue litmus red, and corrode some metals.

Naming Acids

• Acids with H+ and a nonmetal (or CN-) are named with "hydro" and end with "ic acid" (e.g., HCl: hydrochloric acid).

• Acids with H+ and a polyatomic ion: "ate" becomes "ic acid", "ite" becomes "ous acid" (e.g., HClO3: chloric acid).

Arrhenius Bases

Arrhenius bases produce hydroxide ions (OH-) in water. They taste bitter or chalky, feel slippery, turn litmus blue, and phenolphthalein pink.

Naming Bases

• Bases are named as hydroxides (e.g., NaOH: sodium hydroxide, KOH: potassium hydroxide).

Characteristics of Acids and Bases

Brønsted–Lowry Acids and Bases

NH3 as a Brønsted–Lowry Base

In the reaction of ammonia and water, NH3 acts as a base (accepts H+), and H2O acts as an acid (donates H+).

Conjugate Acid–Base Pairs

In any acid–base reaction, there are two conjugate acid–base pairs, related by the loss and gain of H+. One pair occurs in the forward direction, the other in the reverse.

Strengths of Acids and Bases

Strong and Weak Acids

Strong acids dissociate completely in water, while weak acids only partially dissociate. Most acids are weak and have strong conjugate bases.

Strong and Weak Bases

• Strong bases are formed from metals in Groups 1A and 2A and dissociate completely (e.g., NaOH, KOH, Ca(OH)2).

• Weak bases are weak electrolytes and produce few ions in solution (e.g., NH3, Na2CO3).

Chemical Equilibrium and Le Châtelier’s Principle

Le Châtelier’s Principle

When equilibrium is disturbed by changes in concentration, the system shifts to relieve the stress and reestablish equilibrium.

Ionization of Water and pH

Ionization of Water

Water is amphoteric and can act as an acid or base. H+ is transferred from one H2O molecule to another, reaching equilibrium between conjugate pairs.

Neutral, Basic, and Acidic Solutions

The concentration of H3O+ and OH- determines whether a solution is neutral, acidic, or basic.

pH Scale

pH is a logarithmic scale. A change of one pH unit corresponds to a tenfold change in [H3O+]. pH decreases as [H3O+] increases.

Reactions of Acids and Bases

Acid Reactions

• Acids react with certain metals to produce a salt and hydrogen gas.

• Acids react with bases to produce a salt and water (neutralization).

• Acids react with bicarbonate and carbonate ions to produce carbon dioxide gas.

Neutralization

In a neutralization reaction, an acid reacts with a base to produce a salt and water. The salt is formed from the anion of the acid and the cation of the base.

Acid–Base Titration

Titration is a laboratory procedure used to determine the molarity of an acid by neutralizing it with a base and using an indicator to identify the endpoint.

Buffers

Buffer Solutions

Buffers maintain pH by resisting changes when acid or base is added. They consist of a weak acid and its conjugate base (salt), or a weak base and its conjugate acid (salt).

• Example: HC2H3O2(aq) and C2H3O2-(aq)

Organic Compounds

Definition and Elements

An organic compound is made from carbon and hydrogen atoms, and may contain other nonmetals such as oxygen, sulfur, nitrogen, phosphorus, or halogens. Organic compounds are found in many common products.

Covalent Compounds and Bonding

Covalent bonding capacity is determined by the periodic table. Carbon forms four bonds, nitrogen three, oxygen two, and halogens one.

Alkanes

Structure and Naming

Alkanes are hydrocarbons with only single bonds. The covalent bond between carbon atoms is very strong, allowing for many possible compounds. Alkanes can be represented by molecular, expanded, condensed, and line-angle formulas.

Alkanes with Substituents

When an alkane has four or more carbon atoms, side groups (branches or substituents) can be attached. The IUPAC naming system is used for these compounds.

Structural Isomers

Structural isomers have the same molecular formula but different arrangements of atoms. For example, butane (C4H10) has a straight chain and a branched chain isomer.

Naming Cycloalkanes with Substituents

When one substituent is attached to a cycloalkane, its name is placed in front of the cycloalkane name. No number is needed for a single alkyl group or halogen atom.

Drawing Formulas for Alkanes

The IUPAC name provides all information needed to draw the condensed structural formula for an alkane.

Properties of Alkanes

Alkanes have physical properties such as solubility and density that determine their uses. Solid alkanes are used as waxy coatings on fruits and vegetables to retain moisture and inhibit mold.

Alkenes and Alkynes

Structure and Naming

Alkenes contain double bonds, and alkynes contain triple bonds. They are unsaturated hydrocarbons and react with hydrogen gas to become alkanes. The IUPAC names for alkenes and alkynes are similar to alkanes, with "ene" and "yne" endings.

Cis–Trans Isomers of Alkenes

Cis isomers have alkyl groups on the same side of the double bond, while trans isomers have them on opposite sides.

Addition Reactions

Alkenes and alkynes undergo addition reactions, where double and triple bonds are broken to add new atoms.

Aromatic Compounds

Benzene and Derivatives

Benzene is an aromatic compound with a ring of six carbon atoms and alternating double bonds. Aromatic compounds with a benzene ring and a single substituent are named as benzene derivatives.

Naming Aromatic Compounds with Substituents

When toluene, phenol, or aniline has substituents, the carbon attached to the functional group is numbered as carbon 1, and other substituents are named alphabetically.

Concept Maps

Additional info: Academic context and explanations have been expanded for clarity and completeness. All included images are directly relevant to the adjacent content and reinforce key concepts.