QCA7e_ch06_szb_handouts

QCA7e_ch06_szb_handouts - Daniel C Harris Quantitative...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Quantitative Chemical Analysis Seventh Edition Quantitative Chemical Analysis Seventh Edition Chapter 6 Chemical Equilibrium Daniel C. Harris Daniel C. Harris Chapter Highlights • Chemical equilibrium – Equilibrium constants – Equilibrium and thermodynamics – Solubility product –Comp lex format ion –Ac
Background image of page 1

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

View Full Document Right Arrow Icon
2 Equilibria Equilibria Equilibria govern diverse phenomena from protein folding to the action of acid rain on materials to the aqueous reactions used in analytical chemistry • Equilibria for – solubility of ionic compounds – complex formation – acid–base reactions –etc The Equilibrium Constant • Consider a reversible reaction: • We write the equilibrium constant, K, in the form: • Where does it come from?
Background image of page 2
3 The Equilibrium Constant • In equilibrium, the forward and reverse reaction rates are equal: –rate 1 = k 1 [A] a [B] b –rate 2 = k 2 [C] c [D] d •I f ra te 1 =rate 2 , then we get: Units to use • When you evaluate an equilibrium constant: – Concentrations of solutes should be expressed as moles per liter . – Concentrations of gases should be expressed in bars . – Concentrations of pure solids, pure liquids, and solvents are omitted because they are unity . • These conventions are arbitrary, but you must use them if you wish to use tabulated values of equilibrium constants
Background image of page 3

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

View Full Document Right Arrow Icon
4 Manipulating Equilibrium Constants • Consider the reaction: • If the direction of a reaction is reversed, the new value of K is simply the reciprocal of the original value of K. • If two reactions are added, the new K is the product of the two individual values: Example: Combining Equilibrium Constants • The equilibrium constant for the reaction H 2 O H + + OH is called K w (=[H + ][OH ]) and has the value 1.0 10 14 at 25 ° C. • Given that K(NH 3 )= 1.8 10 5 for the reaction NH 3 (aq) + H2O NH 4 + + OH , find K for the reaction NH 4 + NH3(aq) + H + .
Background image of page 4
5 Example: Combining Equilibrium Constants Solution: The third reaction can be obtained by reversing the second reaction and adding it to the first reaction: Equilibrium and Thermodynamics I - Enthalpy • The enthalpy change, Δ H , for a reaction is the heat absorbed or released under constant pressure. • The standard enthalpy change, ° , refers to when all reactants and products are in their standard states. • Positive : –Hea t is • Negative Δ H
Background image of page 5

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

View Full Document Right Arrow Icon
6 Equilibrium and Thermodynamics II - Entropy • The entropy, S, is a measure of the disorder. The greater the disorder, the greater the entropy.
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 34

QCA7e_ch06_szb_handouts - Daniel C Harris Quantitative...

This preview shows document pages 1 - 7. Sign up to view the full document.

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