TODAY
This presentation is the property of its rightful owner.
Sponsored Links
1 / 19

TODAY A new chapter: Equilibrium Writing equilibrium expressions PowerPoint PPT Presentation


  • 79 Views
  • Uploaded on
  • Presentation posted in: General

TODAY A new chapter: Equilibrium Writing equilibrium expressions observing LeChatelier’s Principle Calculating equilibrium constants, K. TODAY A new wrinkle on Equilibrium: Q. Q, from the Q continuum, Star Trek ,The Next Generation No, not that Q . TODAY

Download Presentation

TODAY A new chapter: Equilibrium Writing equilibrium expressions

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


Today a new chapter equilibrium writing equilibrium expressions

  • TODAY

    • A new chapter: Equilibrium

    • Writing equilibrium expressions

    • observing LeChatelier’s Principle

    • Calculating equilibrium constants, K

  • TODAY

    • A new wrinkle on Equilibrium:

    • Q

  • Q, from the Q continuum,

  • Star Trek ,The Next Generation

  • No, not that Q ..


Today a new chapter equilibrium writing equilibrium expressions

  • TODAY

    • A new chapter: Equilibrium

    • Writing equilibrium expressions

    • observing LeChatelier’s Principle

    • Calculating equilibrium constants, K

  • TODAY

  • A quick recap of Monday’s concepts

  • Magnitudes of Keq

  • Q: the reaction quotient

  • Q: how to use it


Today a new chapter equilibrium writing equilibrium expressions

A quick recap on equilibrium expressions:

[products]

Keq

[reagents]

For this reaction:

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

But if reaction goes BOTH to right and to left,

which are reagents and which are products?

By convention”

reagents are species to the left of arrow

products are species to the right of arrow


Today a new chapter equilibrium writing equilibrium expressions

A quick recap on equilibrium behavior:

You observed this chemical system:

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

When you added excess Cl- :

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

When you added excess H2O:

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O


Today a new chapter equilibrium writing equilibrium expressions

The series of reactions observed:

1. CuCl2(H2O)2+ 3H2O

[CuCl(H2O)5]+ + Cl-

2. [CuCl(H2O)5]+ + H2O

[Cu(H2O)6]2++ Cl-

3. [Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]2++ H2O

[CuCl(H2O)52+]

To calculate Keq

[Cu(H2O)62+][Cl]

0.80 M

Need Keq

concentrations

0.28,

NO UNITS!

0.40M x7.1 M

Pure liquids and solids don’t appear in Keq expression:


Today a new chapter equilibrium writing equilibrium expressions

Combining reactions equals multiplying K’s

(a) CuCl2(H2O)2+ 3H2O

[CuCl(H2O)5]+ + Cl-

K1eq

(b) [CuCl(H2O)5]+ + H2O

[Cu(H2O)6]2++ Cl-

K2eq

Kneteq

Net CuCl2(H2O)2+ 4H2O

[Cu(H2O)6]2++ 2 Cl-

[CuCl(H2O)52+ [Cl]

[Cu(H2O)62+][Cl]

K1eq x K2eq

[CuCl(H2O)52+]

CuCl2(H2O)2

[Cu(H2O)62+][Cl]2

K1eq x K2eq

Kneteq

CuCl2(H2O)2


Today a new chapter equilibrium writing equilibrium expressions

Are Your Eyes Misleading You?

What is in the graduated cylinder?

Visible electronic

spectra

mixture can

appear GREEN

Abs

[CuCl(H2O)5+]

[Cu(H2O)62+]

700 nm

400 nm

wavelength


Today a new chapter equilibrium writing equilibrium expressions

Are Your Eyes Misleading You?

What is in the graduated cylinder?

Recall equilibrium concentrations:

[CuCl(H2O)5+]

0.8 M

Keq

0.28

0.4 M x7.1M

[Cu(H2O)62+][Cl]

Visible electronic

spectra

If Keq ~ 1, product concentrations are

similar to reagent concentrations

Abs

mixture can

appear GREEN

[CuCl(H2O)5+]

[Cu(H2O)62+]

700 nm

400 nm

wavelength


Today a new chapter equilibrium writing equilibrium expressions

How large must Keq be for reaction to be “complete”?

Consider this reaction:

[Ni(H2O)6]2++ 6 NH3

[Ni(NH3)6]2++ 6H2O

Keq

2.0 x 108

[Ni(NH3)6]2++ 3 “en”

[Ni(en)3]2++ 6 NH3

Keq

7.3 x 109


Today a new chapter equilibrium writing equilibrium expressions

What is Keq for this reaction: ?

[Ni(H2O)6]2++ 3 “en”

[Ni(en)3]2++ 6 H2O

[Ni(H2O)6]2++ 6 NH3

[Ni(NH3)6]2++ 6H2O

K1 = 2.0 x 108

[Ni(NH3)6]2++ 3 “en”

[Ni(en)3]2++ 6 NH3

K2 = 7.3 x 109

K = K1x K2

[Ni(H2O)6]2++ 3 “en”

[Ni(en)3]2++ 6 H2O

K = K1x K2 = (7.3 x 109)(2.0 x 108)

= 1.5 x 1018


Today a new chapter equilibrium writing equilibrium expressions

What happens if the concentrations are equal:

[CuCl(H2O)5+]= 0.8 M, [Cu(H2O)62+]= 0.8 M, [Cl] = 0.8M

for this reaction:

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

You investigate by calculation:

[CuCl(H2O)5+]

0.8 M

1.25

[Cu(H2O)62+][Cl]

0.8 M x0.8 M

But you know Keq = 0.28 ≠ 1.25: what does this mean?

It’s not at equilibrium!!


Today a new chapter equilibrium writing equilibrium expressions

So under these concentration conditions:

[CuCl(H2O)5+]= 0.8 M, [Cu(H2O)62+]= 0.8 M, [Cl] = 0.8M

[CuCl(H2O)5+]

1.25 > 0. 28 = Keq

[Cu(H2O)62+][Cl]

This tells you one definite thing:

there’s too much in numerator, or,

there’s too much product

How will reaction system species behave?

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

[CuCl(H2O)5+] decreases, [Cu(H2O)62+] increases,

[Cl] increases


Today a new chapter equilibrium writing equilibrium expressions

This is Q!!! Ratio of Concentrations under

Non-Equilibrium conditions

[products]

Q

[reagents]

aA + bB

cC + dD

[C]c[D]d

Q

[A]a[B]b

Q: the Reaction Quotient


Today a new chapter equilibrium writing equilibrium expressions

The reaction quotient Q can be determined for

any set of concentrations

Possible outcomes

[C]c[D]d

1. Q

Keq

[A]a[B]b

[C]c[D]d

2. Q

> Keq

[A]a[B]b

[C]c[D]d

3. Q

< Keq

[A]a[B]b


Today a new chapter equilibrium writing equilibrium expressions

Example problems to be used with reaction:

[Cu(H2O)6]2++ Cl-

[CuCl(H2O)5]++ H2O

Keq = 0.28

A. [CuCl(H2O)5+]= 0 M, [Cu(H2O)62+]= 0.4 M, [Cl] = 0.4 M

B. [CuCl(H2O)5+]= 1 M, [Cu(H2O)62+]= 1 M, [Cl] = 0.5 M

C. [CuCl(H2O)5+]= 0.01 M, [Cu(H2O)62+]= 0.01 M, [Cl] = 0.01 M

Compare this result with earlier equimolar at 0.8M !!


Today a new chapter equilibrium writing equilibrium expressions

Calculations, calculations, calculations,

Many types:

1. Calculating K from equil. concentrations

2. Calc’gKeq from initial and changed concentrations

3. Calc’g final concentrations from initial, change and Keq

4. Calculating a new K from adding 2 reactions


Today a new chapter equilibrium writing equilibrium expressions

The ICEbox method

For these types:

2. Calc’gKeq from initial and changed concentrations

3. Calc’g final concentrations from initial, change and Keq


Today a new chapter equilibrium writing equilibrium expressions

Lots of K’s

Keq – a general equilibrium constant

Kc - equilibrium constant in concentrations

Ksp - equilibrium constant for solubility

Kb - equilibrium constant for OH- formation

Kp - equilibrium constant in partial pressures

Ka - equilibrium constant for H+ dissociation

Kf - formation constant for metal complexes

Not to be confused with:k – rate constants


Today a new chapter equilibrium writing equilibrium expressions

The K “Zoo”

Keq

Kf

Ksp

Kp

Ka

Kc

Kb

little k


  • Login