CHAPTER16CHEM

CHAPTER16CHEM - Ch. 16 Kinetics: Rates and Mechanisms of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Ch. 16 Kinetics: Rates and Mechanisms of Chemical Reactions Chemical kinetics: study of reaction rates, the changes in concentrations of reactants (or products) as a function of time. “16.1 Factors that Influence Reaction Rate” -each reaction has its own characteristic rate, determined by the chemical nature of the reactants We can control 4 factors that affect the rate of a given reaction: 1. Concentration: molecules must collide to react. The more molecules present in the container, the more frequently they collide, and the more often a reaction occurs. So, reaction rate is proportional to the concentration(how much molecules) of reactants: Rate collision frequency concentration 2. Physical state: molecules must mix to collide. When reactants are in same phase, random thermal motion brings them to contact. But if in diff. phases, contact only occurs at interface (surface forming common boundary btw 2 things), so stirring is needed. Here, the more finely divided a solid or liquid reactant, the greater its surface area per unit volume , the more contact it makes with the other reactant, and the faster the reaction occurs. 3. Temperature: molecules must collide with enough energy to react. High temp. increases energy, low temp. decreases. At a higher temp, more collisions occur in a given time b/c temp affects kinetic energy of molecules and thus energy of collisions. Raising the temp increases the reaction rate by increasing the number and, the energy of the collisions: Rate collision energy temperature “16.2 Expressing the Reaction Rate” Rate: a change in some variable per unit time. Reaction rate: the changes in concentrations of reactants or products per unit time: reactant concentrations decrease while product concentrations increase. Rate of Reaction = ∆[A] / ∆t                conc final -conc initial  / t final -t initial       A = mol/L , t = seconds   mol/L ∙s  Rate of Product = ∆[B] / ∆t         Instantaneous rate: rate at which a particular instant during the reaction. The slope of a line tangent to the curve at a particular point gives the instantaneous rate at that time. Initial rate: the instantaneous rate at the moment the reactants are mixed. Average rate: rate over a chosen period of time. Use same equations above.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Expressing rate in terms of reactant and product concentrations: aA + bB cC + dD where a, b, c, d are coefficients of the balanced equation (the # of moles) Rate = -1  ∆[A]  = -1  ∆[B]  = 1  ∆[C]  = 1  ∆[D] “16.3 The Rate Law and its Components” Rate Law (rate equation): (in these cases only) the reaction rate depends only on reactant concentrations and temperature. General reaction:
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/14/2010 for the course CHEM 1A taught by Professor Okamura during the Spring '08 term at UC Riverside.

Page1 / 4

CHAPTER16CHEM - Ch. 16 Kinetics: Rates and Mechanisms of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online