#!/usr/local/bin/perl # This is just a cgi generated HTML submission form. You can do the same # thing with HTML, but for the sake of distribution, I am doing it this way # so that all the files can remain together. # The only thing tricky about the FORM which you use as your user # interface is that each radio multiple choice button series must have NAME # argumnets corresponding to the first field in the answers database. # Also, the VALUE must correspond exactly to the corresponding field in the # answers database. # First print out the HTTP headcer, then print out the form print "Content-type: text/html\n\n"; print qq! Chemistry 104: Buffer Questions
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An aqueous solution of a weak acid and its conjugate base can provide protection agains large pH changes when moderate amounts of acid or base are added. Such solutions are called buffered solutions. The amount of added acid or base that can be added without a large pH change depends on the amount of the weak acid/base pair in the solution. The pH range which is maintained is dependent on the identity of the acid/base pair.

1. Which of the following solutions could accomodate the largest amount of added acid or base (without a large change in pH)?
0.1 M NH3 and 0.1M NH4+
0.5 M NH3 and 0.5M NH4+
0.1 M NH3 and 0.1 M NaOH
0.5 M NH3 and 0.5M Na0H

2. A buffer solution is made from formic acid and sodium formate. Added acid will react with:
sodium hydroxide
sodium formate
formic acid
hydrochloric acid

Consider the following:
  1. HCl and NaOH
  2. CH3COOH and CH3COONa
  3. NH3 and NH4Cl
Of these three pairs of compounds, which could be combined to make a buffer?
all of them
1 and 2
2 and 3
only 3

4. A buffer of pH 4.6 is prepared from a weak acid HA and its conjugate base A-. To increase the pH of this buffer
increase the ratio of HA to A-.
decrease the ratio of HA to A-.
add HNO3
add HCOOH.

5. A buffer of pH 5.2 is to be prepared. Which of the following compounds should be used?
HX (Ka=6.1 x 10-6)
HY (Ka=2.9 x 10-2)
HZ (Ka=4.9 x 10-4)
B (Kb=6.3 x 10-6)

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