1 / 11

Rates of Reactions

Rates of Reactions. Part II of Unit II. Reaction Rate. Is the speed at which a chemical reaction occurs Measured by the change in concentration of a reactant or product over time Rate of rxn = Δ [A] /∆t * square brackets indicate the concentration of reactant or product ‘A’

payton
Download Presentation

Rates of Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Rates of Reactions Part II of Unit II

  2. Reaction Rate • Is the speed at which a chemical reaction occurs • Measured by the change in concentration of a reactant or product over time • Rate of rxn = Δ[A] /∆t * square brackets indicate the concentration of reactant or product ‘A’ • Units of mol/s or mol/L·s which can also be written as: mol L-1s-1

  3. Factors that affect the Rate of Reaction • Nature of Reactants • Tendencies toward bond formation • Ability of an atom to gain or lose electrons • Surface Area - Ability of reactants to meet • Solid reactant with a gas reactant would be much slower than two gas reactants • Surface area of a solid is increased by decreasing the particle size

  4. http://www.youtube.com/watch?v=Jg7mLSG-Yws

  5. Temperature • Increasing the temperature generally increases the rate of reaction • Recall that kinetic molecular theory states that molecules move faster at higher temperatures, thus have more kinetic energy. This allows molecules greater ability to react.

  6. Catalyst • A catalyst is a substance that increases the rate of a reaction but is not consumed in the reaction. • Examples are: • platinum in catalytic converters, which convert carbon monoxide to carbon dioxide a lesser of two evils. • Enzymes, which are proteins that attach to a reactant(s) and allow for a chemical rxn to occur then unattach.

  7. Concentration • Generally increasing the concentration of reactants will speed up a rxn • As a rxn proceeds, the concentration of reactants decreases and consequently so does the rate • If you were to graph concentration of reactant vs. time it would be curved...

  8. Concentration vs. Time

  9. Average vs Instantaneous Rates of Reactions • The rate of reaction can be determined by calculating the slope of a concentration vs. Time graph. • Average rates are determined by the slope of a secant which is the change of concentration over a longer period of time. • Instantaneous rates are determined by drawing a tangent to the curve and calculating the slope of the tangent.

  10. Drawing a tangent

  11. Complete: • Thought lab on page 270, procedure 1-5 and analysis 1-4.

More Related