Chemistry 12

Catalyst

(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected -Is a substance that increases the reaction rate by providing a lower energy pathway. -Always regenerate in the last step. -increases the rate of forward and reverse reactions. *Doesn't change the energy of the reactants or products.

Endothermic

(of a chemical reaction or compound) occurring or formed with absorption of heat ΔH positive, Reactants+Heat-----Products

Soluble

(of a substance) capable of being dissolved in some solvent (usually water) [greater than 0.1M]

Molecular Solution

-A solution containing only neutral molecules -do not conduct electricity General Rules: non metal and non metal, Organic compounds.

Salt

-Can be "soluble", or has "low solubility"

Potential Energy (PE)

-Energy existing as a result of an objects position in space. -The sum of attractive and repulsive forces existing among particles

Dynamic Equilibrium

-Equilibrium situation in which microscopic changes occur but macroscopic do not. Macroscopic---Atomic level Microscopic---visible or large scale i.e. temp,conc., pH,mass, pressure.

Aqueous Phase

-Is a completely dissolved solution -Move freely in solvent -Strong +/- attraction

Inhibitor

-Reduces reaction rate by combining with the catalyst or a reactant to prevent the reaction from occurring. i.e. poison or antibiotics

Activation Energy

-The minimum amount of energy required by the reactants to react. -Energy difference between activated complex and the reactants. -the minimum amount of energy required to start a chemical reaction -The higher the (Ea) the slower the rate

Activated Complex

-a high energy transitional structure in a chemical reaction where old bonds are breaking and new bonds are forming -an unstable arrangement of atoms that exists momentarily at the peak of the activation-energy barrier; an intermediate or transitional structure formed during the course of a reaction -This is a short lived high energy molecule -Unstable (top of PE diagrams)

Enthalpy

-change in energy of a chemical reaction (ΔH) -Total energy of system (KE+PE) ΔH= Hproducts-Hreactants

Rate Determining Step (Reaction Mechanism)

-slowest step -Largest (Ea) -ONLY changing the reactants of the rate determining step will affect the reaction.

Ionic Solution

-solution that contains ions -able to conduct electricity General Rules: Metal and non-Metal, also polyatomic ions

Characteristics of Equilibrium

1) Closed system 2) Constant Macroscopic properties 3)Rate of forward reaction = Rate of reverse reaction

Solubility

2 types of solutions: Ionic and Molecular solutions - the quantity of a particular substance that can dissolve in a particular solvent (yielding a saturated solution) -units M, mol/liter, g/liter

Neutralization equation

Acid + Base --> Water + Salt

Arhenius Theory

Acid - substance that produces a proton (H+) in water Base - substance that produces a hydroxide ion (OH-) in water

Reaction Rate

Change in quantity of reactants or products over time.

Overall Reaction (Reaction Mechanism)

Cross out catalyst and Reaction Intermediates, then add up reactants and products. -remember that it is very unlikely that 6 particles will collide at one time. Reason for Reaction Mechanism. -(Ea) is equal to the highest activated complex-PE reactants.

Kinetic Energy (KE)

Energy a system possesses due to movement

Homogenous Reaction

Is a reaction in which all reactants are in the same phase. i.e. Two gases, two liquids that completely dissolve in each other, or two substances that both dissolve in water.

Solubility Product

Ksp; constant for the dissolving of a solid in water

Methods of measuring reaction rates

Mass Change, Color Change, Temperature Change, Pressure Change, Acidity Change

Keq<1

Reactants are greater than products

Factors affecting Reaction Rates

Temperature, concentration, pressure, surface area, phase consideration, catalyst or inhibitor.

Keq Trial=Keq

The reaction is at equilibrium

Keq Trial<Keq

The reaction must shift right to increase value

Reaction Time

Time it takes for a reaction to come to completion. Inversely proportional to reaction rate.

Low Solubility

[less than 0.1M], will form a precipitate (ppt-solid) in solution

Keq

[products]/[reactants] only temperature affects it's value

Saturated Solution (less than 0.1M)

a solution which has dissolved the "maximum amount" of a substance. -is a solution in which there exists a dissolved substance in equilibrium with the undissolved substance. -equilibrium must exist between dissolved and undissolved substance * some undissolved substance in equilibrium must be present.

Bronsted Lowry Theory

defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor

Ksp

equilibrium constant (larger the Ksp the more soluble, the smaller the less soluble)

Chemical Equilibrium

in a closed system the decreasing forward and increasing reverse reaction rates eventually become equal so that no further change in concentration takes place. Equilibrium state is dynamic not static.

Hydrolysis

is a reaction between salt and water to produce an acidic, basic or neutral solution.

Heterogenous Reaction

is a reaction in which all reactants are present in different phases. i.e. Solid and Liquid--Liquid and Gas--Solid and Gas. or two liquids that do not dissolve in each other (are immiscible)

Collision Theory

is the basic premise that in order for a reaction to occur reacting reactant molecules/particles must collide. -in order for collision to be successful you must have: 1) necessary kinetic energy 2) proper geometry -increase # of collisions and increase in reaction rate = increase in concentration of reactant. -increase in temp=increase in kinetic energy therefore the reaction rate.

Sulphuric Acid-(H2S04)

oil of vitriol - good dehydrating agent (removes water) -strongly exothermic when mixed with water -reacts with some metals, slowly -good electrolyte -concentrated form chars some typers of organic material, dehydrating USES p

Keq>1

products are greater than reactants

Keq=1

products equal reactants

Potential Energy Diagrams

shows the change in potential energy as the reactants are converted to products. Exothermic= energy released, lost energy. Reaction proceeds from high reactants to low products on the potential energy scale Endothermic= energy is absorbed, gain energy. Reaction proceeds from low reactants to high products on the potential energy scale.

Reaction Intermediates

species that are formed in one step of a reaction mechanism and consumed in another -Appears first as a product and second as a reactant -not present in overall reaction

Bond Energy

the energy required to break a chemical bond and form neutral isolated atoms

Common Ion Effect

the lowering of the solubility of an ionic compound as a result of the addition of a common ion

Le Chatelier Principle

the principle that if any change is imposed on a system that is in equilibrium then the system tends to adjust to a new equilibrium counteracting the change

Keq trial > Keq

the reaction must shift left to decrease value

Reaction Mechanism

the step-by-step sequence of reactions by which the overall chemical change occurs

Solubility Chart

used to predict the solubilities of salts

Exothermic

ΔH negative, Reactants----- Products+Heat , (of a chemical reaction or compound) occurring or formed with evolution of heat