slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 17 Equilibrium 17.1 How Chemical Reactions Occur Particle collisions PowerPoint Presentation
Download Presentation
Chapter 17 Equilibrium 17.1 How Chemical Reactions Occur Particle collisions

Loading in 2 Seconds...

play fullscreen
1 / 22

Chapter 17 Equilibrium 17.1 How Chemical Reactions Occur Particle collisions - PowerPoint PPT Presentation


  • 88 Views
  • Uploaded on

Chapter 17 Equilibrium 17.1 How Chemical Reactions Occur Particle collisions 1. Particles MUST collide for a chemical reaction to occur. 2. Orientation of particle collision is important. 3. Effectiveness of particle collision is important.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 17 Equilibrium 17.1 How Chemical Reactions Occur Particle collisions' - oleg-mclaughlin


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Chapter 17 Equilibrium

17.1 How Chemical Reactions Occur

Particle collisions

1. Particles MUST collide for a chemical reaction to occur.

2. Orientation of particle collision is important.

3. Effectiveness of particle collision is important.

slide2

Figure 17.2: (a)Two BrNO molecules approach each other at high speeds. (b) The collision occurs. (c) The energy of the collision causes Br-N bonds to break and Br- Br bonds to form. (d) The products: one Br2 and two NO molecules.

slide4

17.2 Conditions that Affect Reaction Rates

Concentration- Increasing concentration will increase the number of particles that are present, allowing for more collisions

Temperature- increasing the temperature gives the particles more kinetic energy; the collisions, when they occur, will be more effective

Catalyst- a catalyst makes a chemical reaction occur faster (orientation of reacting particles) and is not consumed during the reaction. A catalyst is recoverable (write it over the arrow)

Enzymes- an organic catalyst (catalase, lipase, diastase)

Energy diagram (catalyzed & uncatalyzed)(note especially the difference between exothermic and endothermic reactions)

slide5

Figure 17.4: Comparison of the activation energies for an uncatalyzed reaction and for the same reaction with a catalyst present.

slide6

17.3 Heterogeneous Reactions

Homogeneous- all substances are in the same phase of matter

Example:

N2(g) + 3H2(g)  2NH3(g)

Heterogeneous- substances are in different phases of matter

Example:

CaCO3(s)  CaO(s) + CO2(g)

slide7

17.4 The Equilibrium Condition

17.5 Chemical Equilibrium: A Dynamic Condition

Physical equilibrium (see demo in class: vaporization & condensation, discussed in Chapter 14)

Chemical equilibrium- a dynamic state where the concentrations of all reactants and products remain constant

The rate of the forward reaction equals the rate of the reverse reaction. All chemical species will be present at the same time. Technically all chemical reactions are reversible (although, many of them do not do this spontaneously; they require too much energy input to react in the reverse direction.)

Example:

2Mg(s) + O2(g)  2MgO(s)

2Na(s) + Cl2(g)  2NaCl(s)

slide8

Figure 17.8: (a) Net transfer of molecules from the liquid state to the vapor state. (b) The amount of the substance in the vapor state becomes constant. (c) The equilibrium state.

slide9

Figure 17.9: (a) Equal numbers of moles of H2O and CO are mixed in a closed container. (b) The reaction begins to occur. (c) The reaction continues, and more reactants are changed to products. (d) No further changes are seen as time continues to pass.

slide11

17.6 The Equilibrium Condition: An Introduction

17.7 Heterogeneous Equilibria

For the generic reaction:

aA + bB  cC + dD

Equilibrium expression- temperature defined; no unit

K =

Do not include pure solids or pure liquids (only gases & solutions)

Large value of K- products are favored

Small value of K- reactants are favored

slide13

17.8 Le Chatelier’s Principle

When a change is imposed on a system at equilibrium, the position of the equilibrium shifts in a direction that tends to reduce the effect of the change

Temperature

Problem:

Pressure

Change in volume

Problem:

Increase # moles of reactant

Decrease # moles of product

For example, in the Haber process:

N2(g) + 3H2(g)  2NH3(g)

slide14

For example, in the Haber process:

N2(g) + 3H2(g)  2NH3(g)

slide15

Figure 17.11: (a) Initial equilibrium mixture. (b) Addition of N2. (c) New equilibrium position.

slide18

Figure 17.13: (a) A mixture of NH3(g), N2(g), and H2(g) at equilibrium. (b) The volume is suddenly decreased. (c) The new equilibrium position.

slide19

17.9 Applications Involving the Equilibrium Constant

17.10 Solubility Equilibria

Because: AgCl(s)  Ag+(aq) + Cl-(aq)

And Ag+(aq) + Cl-(aq)  AgCl(s)(precipitates easily)

Therefore, it is an equilibrium system:

AgCl(s)  Ag+(aq) + Cl-(aq)

Ksp

(do not use pure solids in an equilibrium expression)

Example:

slide20

Working backwards (know value of Ksp, determine solubility in g/ml or mole/liter)(This is the most difficult math in the entire course!)

Example:

slide21

Common Ion Effect

Remember LeChatelier’s Principle: the presence of a common ion may shift a system in equilibrium

Water softening systems (sodium replacement)

Diprotic & triprotic acid dissociation (presence of hydrogen ion actually inhibits further dissociation (common ion).

More complex systems (estuaries, kidney dialysis, etc.)

slide22

Weak Acid equilibria, Ka

Weak Base equilibria, Kb

Water equilibrium, Kw