Lecture 2 presented

In water naoh na oh solid oh h h 2o net

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Unformatted text preview: water to make 1 liter of solu7on. 39 39 Acid/Base chemiostry When acids dissolve in water, they release hydrogen ions: H+ (protons). H+ ions can aRach to other molecules and change their proper7es. Bases accept H+ ions. 40 40 Strong acids, dissociate and increase the [H+] HCl " H + Cl + ! Gas HCl is a strong acid: the dissolu7on is complete. 41 41 What happens if you bubble H2 gas in water? Weak Acids Weak acids: not all the acid molecules dissociate into ions. Organic acids have a carboxyl group: -R-COOH -R-COO- + H+ 43 43 Strong Bases NaOH is a strong base (it accepts H+). In water: NaOH " Na + OH + ! Solid OH + H ! H 2O " + Net result is less H+ in the environment 44 44 Weak Bases Weak bases: • Bicarbonate ion HCO3 " + H + ! H 2CO3 • Ammonia NH 3 + H ! NH 4 + + • Compounds with amino groups " NH 2 + H ! NH 3 + + 45 45 What Makes Water So Important for Life? Water has a slight tendency to ionize. H 2O " H + OH + ! Two molecules are actually involved: 46 46 Water can act as both acid and base 47 47 How do we measure acids and bases? pH = nega7ve log of the molar concentra7on of H+ ions. pH = -log [H+] H+ concentra7on of pure water is 10–7 M, its pH = 7. Lower pH numbers mean higher H+ concentra7on, or greater acidity. 48 48 pH 1 M HCl solu7on: H+ concentra7on = 1 M pH = 0 1 M NaOH solu7on: H+ concentra7on = 10–14 M. pH = 14 49 49 Figure 2.16 pH Values of Some Familiar Substances 50 50 What Makes Water So Important for Life? Living organisms...
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This note was uploaded on 10/11/2011 for the course BIS 2A taught by Professor Grossberg during the Summer '08 term at UC Davis.

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