pH 2.5 and a total buffer concentration of 0.20 M for a biological
experiment. You have bottles of the four compounds illustrated
below (in pure form, all liquids), 1.00 M HCI, 1.00 M NaOH,
distilled water, a balance, and volumetric glassware.
a. First you select one of the compounds illustrated
above as the buffer. Circle the compound you will use
above.
b.Every buffer is made up of a weak acid and its
conjugate base. Draw the structures of these two species for this
buffer (include all electron pairs and label formal charges) in the
boxes below and estimate the pKa of the acid.
c.In the first step of preparing the buffer, you will
measure out 0.200 moles of the compound and dissolve it in water to
make an initial 500.0 mL solution. How much (in g) of the compound
will you need to measure out?
d. When you dissolve the compound you selected in part a
in water to make the initial 500.0 ml solution you decide to
measure the pH. Predict the pH of the initial 500.0 mL solution to
one decimal place.
e.In the next step of preparing the buffer at the
desired pH you add either 1.00 M NaOH or 1.00 M HCI. Which one will
you add and what volume (in mL) will you add to the initial
solution?
Which will be added? (circle one) NaOH or HCI.
What volume will be
added?
F. Draw the chemical reaction (using structures) that
takes place between the NaOH or HCI (per your selection in part e)
and the buffer compound you selected in part a. Be sure to draw all
electron pairs, use curved arrows to show the reaction taking
place, and label charged atoms with formal charges.
g.You complete the preparation of the buffer by diluting
the solution prepared in part e to 1.00 L with distilled water in a
volumetric flask. You decide to test the buffer before using it so
you take 100.0 mL of the buffer, measure its pH and then add to it
2.00 mL of the 1.00 M NaOH and measure its pH again. Calculate the
pH before and after the addition to one decimal place.
- You Are Interested In Preparing 1 00 L Of A Buffer With Ph 2 5 And A Total Buffer Concentration Of 0 20 M For A Biologic 1 (102.97 KiB) Viewed 73 times