Sunday, March 14, 2010

Which of these are true?

Which of the following are TRUE regarding buffers? (Check all that apply):





-Buffers help keep the pH constant.


-A 50/50 mixture of 1M acetic acid and 1M sodium hydroxide will make a buffer.


-A 50/50 mixture of 1M acetic acid and 1M sodium acetate will make a buffer.


-A 60/40 mixture of 1M ammonia and 1M ammonium nitrate will make a buffer.


-pH buffers are added to shampoos and other cosmetic products.


-Buffers are often present in biological systems.


-Man-made buffers were first invented by Robert Boyle.


-A buffer in chemistry is a machine used to polish shoes and equipment.


-Buffers help keep the pOH constant.


-Buffers are a mixture of an acid and its conjugate base in roughly equal proportions.





which of these are true?

Which of these are true?
Buffer solutions are solutions which resist change in hydrogen ion and the hydroxide ion concentration (and consequently pH) upon addition of small amounts of acid or base, or upon dilution. Buffer solutions consist of a weak acid and its conjugate base (more common) or a weak base and its conjugate acid (less common). The resistive action is the result of the equilibrium between the weak acid (HA) and its conjugate base (A−):





HA(aq) + H2O(l) → H3O+(aq) + A−(aq)





Any alkali added to the solution is consumed by hydrogen ions. These ions are mostly regenerated as the equilibrium moves to the right and some of the acid dissociates into hydrogen ions and the conjugate base. If a strong acid is added, the conjugate base is protonated, and the pH is almost entirely restored. This is an example of Le Chatelier's principle and the common ion effect. This contrasts with solutions of strong acids or strong bases, where any additional strong acid or base can greatly change the pH.





When writing about buffer systems they can be represented as salt of conjugate base/acid, or base/salt of conjugate acid. It should be noted that here buffer solutions are presented in terms of the Brønsted-Lowry notion of acids and bases, as opposed to the Lewis acid-base theory (see acid-base reaction theories). Omitted here are buffer solutions prepared with solvents other than water.





Their resistance to changes in pH makes buffer solutions very useful for chemical manufacturing and essential for many biochemical processes. The ideal buffer for a particular pH has a pKa equal to the pH desired, since a solution of this buffer would contain equal amounts of acid and base and be in the middle of the range of buffering capacity.





Buffer solutions are necessary to keep the correct pH for enzymes in many organisms to work. Many enzymes work only under very precise conditions; if the pH strays too far out of the margin, the enzymes slow or stop working and can denature, thus permanently disabling its catalytic activity. A buffer of carbonic acid (H2CO3) and bicarbonate (HCO3−) is present in blood plasma, to maintain a pH between 7.35 and 7.45.





Industrially, buffer solutions are used in fermentation processes and in setting the correct conditions for dyes used in colouring fabrics. They are also used in chemical analysis and calibration of pH meters.





now that i have told u all that is there to it


try answering it ur-self
Reply:I checked all but the wrong ones. I'll say all!



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