GenChem Reviewer 3rd Qtr

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Solutions

Solutions

- These are mixtures of two or more substances evenly distributed throughout a single phase

Solute

- It is the substance dissolved in a solution and is usually present in smaller amount

Solvent

- Is the dissolving medium

Unsaturated Solution

- It contains less solute than the solvent’s capacity to dissolve

Saturated Solution

- It contains the maximum amount of solute that the solvent can dissolve at a certain temperature

Supersaturated Solution

- It contains more dissolved solute that is present in a saturated solution

CONCENTRATION OF SOLUTIONS

- It is a measure of the amount of solute in a given amount of solvent or solution

SOLUTION STOICHIOMETRY

- Practically follows the same procedure in quantifying the amount of solute and solvent present in aqueous solutions or establishing then concentration of the precipitate in a gravimetric or in a precipitate reaction.

Expanding the Solvent

- Overcoming the intermolecular forces in the solvent to give room for the solute

Expanding the Solute

- Separating the solute into individual components

Endothermic Process

- It requires energy to overcome the forces in expanding the solvent and the solute

Exothermic Process

- It releases energy after the formation of new solute-solvent interactions.

COLLIGATIVE PROPERTIES OF SOLUTIONS

- Properties that depend on the number of particles of solute present but not on them kind and nature of solute

Vapor Pressure Reduction

- The relationship between vapor pressure of the solution and the vapor pressure of the solvents depends on the concentration of the solute in the solution. Non-volatile substance has lower vapor pressure than that of volatile substance.

Boiling Point Elevation

- One mole of any non-volatile, non-electrolyte solute will elevate the boiling point of a given amount of boiling point of a given amount of solvent by a constant factor depending on what the solvent is, also termed ebullioscopic constant

Freezing Point Depression

- One mole of any nonelectrolyte will lower the freezing point of a given amount of solvent by constant amount also termed as cryoscopic constant.

Osmotic Pressure

- The osmotic pressure will be applied to the more concentrated solution so that the solvent flows to the more concentrated solution to the less concentrated solution

System

- The part of the universe being studied or to which attention is being focused

- It is a body of matter whereby observations are made

Surroundings

- It is everything else in the universe

- It comprises of everything that is not a component of the system

FIRST LAW OF THERMODYNAMICS

- The change in energy of a system is equal to the heat absorbed (q) by the system and the work (w) done on it.

Enthalpy (H)

- The amount of heat absorbed or released by a chemical reaction at constant atmospheric pressure

Enthalpy of a Reaction

- The difference between enthalpies of the products and the reactants

- Governed by the law of conservation of energy

STANDARD MOLAR ENTHALPY OF REACTION

- Can be calculated by subtracting the sum (Σ) of the enthalpies of formation of the products and the formation of the products and the sum of the enthalpies of formation of the reactants

SECOND LAW OF THERMODYNAMICS

- It states for any spontaneous process, there is a net increase in the total entropy of the system and the surroundings.

Spontaneous Process

- Refers how it occurs on its own without the help of any external factors

- Is irreversible; only has one direction

Non-spontaneous Process

- It cannot proceed unless there is a driving force or outside help that acts on the system

ENTROPY (S)

- It is a measure of molecular randomness

THIRD LAW OF THERMODYNAMICS

- States that the entropy of a system approaches a constant value as the temperature approaches absolute zero (0 K) or -273.15 °C

spontaneous

- Chemical reactions that produce higher number of product particles than that of the reactant particles are usually ---.

STANDARD MOLAR ENTROPY

- It is the entropy of one mole of a substance at the standard conditions (1 atm and 25°C)

GIBBS FREE ENERGY (G)

- It is a portion of the total energy of a system that is available to do useful work

Josiah Willard Gibbs

Gibbs Free Energy is named after the American mathematician and physicist ---

Rate Law for a Reaction

- Is a mathematical expression that shows how the rate of reaction depends on the concentration of the reactants.

Zero-order reaction

Has a constant rate that is equal to its rate constant regardless of changes in the concentration of the reactant.

First-order reaction

The rate doubles when the concentration is doubled; triples when the concentration is tripled, so on.

Second-order reaction

Increasing the reactant concentration to twice as much as quadruples the original reaction rate.

INTEGRATED RATE LAW

§  Relates the time it takes for an amount of chemical to be consumed and the remaining amount of reactant that would be left after a certain period of time.

§  It is derived from the rate law expression for the reaction.

Half-life

the time for a reactant to become half of its original amount

The Collision theory

§  It explains how reactant concentration affects the rate of a reaction. The frequency of particle collision will be higher if there are more reactants present in the system.

Activation Energy

§  The reactant particles must also have sufficient energy during collision. They must be able to surpass an energy barrier, called the activation energy of the transition state to successfully form the products.

Catalysis

Catalysts speed up the rate of chemical reaction by providing an alternate route for the reaction to occur with lower activation energy

Arrhenius Equation: Effect of Temperature on Reaction rate

Increasing the temperature of the reaction system causes the reactant particles to move faster, thereby increasing the chances of sufficiently energetic and successful collision.

Heterogeneous Catalysts

§  A catalyst that is different from that of the reactants and products.

Homogeneous Catalysts

§  The catalyst is the same phase as that of the reactants and products.