** A CHEMISTRY RAP ** substances found in so many places can be called either acids or bases acid is a proton donator base is a proton acceptor why would a compound want to give away its proton actually makes sense, this ain’t no con atoms come together, share their electrons makes a compound, forms a covalent bond electronegative, one of those atoms is most wants to hold both electrons, brings ‘em real close don’t know which one they’re near more look at the periodic table to be sure electronegativity increases as you go right and up, chlorine pulls them electrons real tight shares them with hydrogen, you got HCl oh yeah a proton is a hydrogen ion, well that’s why HCl is such a strong acid chlorine takes hydrogen’s electron for itself kid in a polar solvent like water it depends H+ floats around lookin’ for a friend H+ means it’s a hydrogen ion brother lost an electron, it really needs another lookin’ to bind, ions are highly unstable lookin’ everywhere, even under the table acids and bases dissociate in water only strong ones do completely, maintain order you can figure out how many protons there are to calculate pH, you’re not very far pH is a scale, acids on the low side 0 to 14, bases on the high 7 in the middle, the pH of water weak acids and bases on the border 0.01 molar HCl a strong acid really dissociates well in water that means 0.01 H+ concentration man this is easier than multiplication pH= -log proton concentration plug in –log (0.01) almost done, I aint playin’ you pH of this solution is 2 weaker acids don’t dissociate completely need dissociation constant to figure it out neatly dissociation constant equals Ka Ka equals [H+] [A-] over HA that means you have a relation hydrogen ions, conjugate base in an equation and the undissociated acid molecules that’s the HA, you’ll get it, just follow these rules. figure out pH for acetic acid concentration of that vinegar is 0.2 molar kid Ka is 1.8 x 10-5 set up and plug in, that ain’t no jive number of hydrogen ions is equal to x same as conjugate base you know what’s next concentration of weak acid doesn’t change fool Ka equals x2 over 0.2 solve for x and you get number of hydrogen ions now you know how to get your pH on. all you gotta do is take negative log calculated pH is 2.7, dawg ** And Finally app ka 2nd chp o gya :D **
Posted on: Sun, 30 Mar 2014 15:48:54 +0000
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