chemistry ch16

Kinetics (def)

Study of rates of reaction and steps by which they occur

Kinetics

Addresses how a reaction proceeds from reactants to products

Thermodynamics

Concerned only with the change in energy from reactants and products

Questions that kinetics and thermodynamics ask

T: Can it react

K: will it react and how fast will it react

Collision theory

1. Particles must collide first in order to react

2. They have to collide with proper orientation for arrangement of atoms and electrons

3. They have to collide with enough energy to form products

Activation energy

Minimum amount of kinetic energy colliding particles need to start a reaction

Activated complex

An intermediate structure that forms as reactants transition to products

Unstable and short-lived

Rate of reaction

Measure of how quickly reactants change into products

Factors affecting reaction rate

Nature of reactant, concentration, temperature, surface area, and presence of catalyst

Nature of reactant

Reactive substance react more quickly but also depends on combination of elements

Concentration

The greater the concentration, the greater the likelihood of effective collisions

Temperature

Higher temperature means more kinetic energy and results in fast-moving particles that collide with more energy, thus more likely to have effective collisions

Surface area

the more exposed area and contact possible between particles, the more likely effective collisions will occur thus a faster reaction rate

Catalyst

Substance that changes a reaction’s rate without being consumed by the reaction

Present during reaction but not reactant or product

Types of catalysts

Homogeneous, heterogeneous , enzymes(biological substance that allows reaction to occur faster at low temperature), inhibitors (reduction a catalyst’s undesirable effect

Reaction mechanism

Series of steps (elementary steps) that make up a reaction

Complex reaction/ net reaction

Sum of elementary steps excluding the intermediates

Intermediate

Substance that form in one step and consumed in the next

Reaction order

Indicate how reaction rate is affected by the reactant’s concentration

Rate law

An equation mathematically describes how fast a reaction occurs