BB lecture 9-7 water,pH

BB lecture 9-7 water,pH - Chapter 3 pH properties of water...

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Chapter 3 – pH, properties of water, and concentrations of solutions Learning objectives: • Know the definitions of: Acids , bases , and buffers . • Understand the basis of the pH scale and how it is used as a measure of acidity/alkalinity of solutions. Know/describe emergent properties of water resulting from hydrogen bonding . • Be able to explain the difference between heat and temperature. Know three ways to calculate the concentration of solutes in an aqueous solvent. Examples: 5% solution 1.0 Molar solution 1.0 Osmolar solution Terms to know include: hydrophobic, hydrophilic, cohesion, adhesion, calorie, kilocalorie (aka Calorie – w/ capital ‘C’), specific heat, heat of vaporization…

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A water molecule may dissociate into a hydronium ion and a hydroxide ion: We will use the older convention of representing dissociation into hydrogen ions and hydroxide ions. H 2 O ------ H + + OH - Note this rx is reversible In pure water, [H + ] = 10 -7 M, and [OH - ] = 10 -7 M, and the product is 10 -14 M The negative log 10 [H+] refers to the acidity/alkalinity of a solution – called “pH” Each pH unit represents a tenfold difference in H+ and OH- concentrations .
In a neutral solution (pH = 7), [H + ] = 10 -7 M and [OH - ] = 10 -7 M Adding acid [anything that “donates” H+] to a solution shifts the balance toward H + and leads to a decline in OH - . If [H + ] = 10 -5 M, then [OH - ] = 10 -9 M…………pH = 5 an acidic solution Hydroxide concentrations decline because some of the additional H+ combines with hydroxide to form water.

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This note was uploaded on 10/06/2010 for the course BIO 311C taught by Professor Satasivian during the Fall '08 term at University of Texas.

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BB lecture 9-7 water,pH - Chapter 3 pH properties of water...

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