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CHAPTER 16: AQUEOUS IONIC EQUILIBRIUM 16.1: The Danger of AntiFreeze *antifreeze that’s improperly stored or that leaks from car radiator *antifreeze in cars: aq sol of ethylene glycol (alcohol) *sweet taste, attracts dogs, cats, kids (vulnerable to this toxin) *1 st stage of eg poisoning: state of “drunkenness” ( the alcohol compound affects brain like alcoholic beverage) *after its metabolized, more deadly symptoms *oxidized in liver to glycolic acid, which enters blood stream *blood pH important/tightly regulated cuz proteins require narrow pH range to function *between 7.36-7.42 (this constant pH maintained by buffers—chem system that resists pH changes—will neutralize added acid or base imp buffer in blood (weak acid)CARBONIC ACID (neutralizes base by forming water and bicarbonate ion) and (conjugate base) BICARBONATE ION(neutralizes acid by forming carbonic acid) see eqs on page 716 *when glycolic acid enters blood stream its tendency to lower the pH of the blood countered by the buffering action of the bicarbonate ion *if a lot of g acid, then overwhelms capacity of buffer, causing pH to drop dangerously low *low ph acidosis (bloods capacity to carry oxy is reduced because it affects the equilibrium between hwmoglobin and oxygen 16.2 Buffers: Solutions that resist pH change *buffers contain SIGNIFICANT amounts of both a weak acid and its conjugate base (or a weak base and its conjugate acid) *weak acid itself (though it ionizes to form some of its conjugate base) does not contain sufficient base to be a buffer (similarly, weak base doesn’t have enough acid) *if amount of added base is less that the amount of weak acid (buffer) in solution, the buffer would neutralize the acid, and the resulting pH change would be small (same vice versa)
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Calculating the pH of a buffer solution Example: how to calculate pH of sol with both acid and base? A sol initially containing See page 720 Henderson-Hasselbalch Equation See page 721 for ex[lanation of equation PH = pKa + log [base]/[acid] Base = conjugate base, acid = conjugate acid of the base Allows us to calculate the pH of a buffer solution from the initial concentrations of the buffer components as long as x is small approximation *try using equilibrium method (more useful/accurate?) *remember that x is small approximation applies to problems in whilch both of the following are true (a) the initial concentrations of acids (and or bases) are not too dilute) and (b) the equi constant is small Calculating pH Changes in a Buffer Solution
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