Question 1: You are interested in preparing 1.00 L of a buffer with pH 105 and a total buffer concentration of 0.20 M fo

Post by **answerhappygod** » Tue May 17, 2022 9:23 am

: Question 1 You Are Interested In Preparing 1 00 L Of A Buffer With Ph 105 And A Total Buffer Concentration Of 0 20 M Fo 1 (79.58 KiB) Viewed 72 times

Question 1: You are interested in preparing 1.00 L of a buffer with pH 105 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. (8 pts each, 56 pts) O H HON H inio H CI HN ...F H F 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.

Weak acid: all termal change Conjugate base: 20 : 0 : 18 EF H 4 G H H/ H pKa estimate 4.7 ou 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? 78 0.2 ( 12.01X2 + 4x1,298 +2x16)= 2.0194 Mass of compound needed: 2.09 12.09 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 X= 7.981048/0 0. 200ml Conc= +7 = 0.400 M 0 Jogol pka = 4.7 Kas 10-4.7 log CH3COOH 13. CoolH+40 2 CH₂ Cat +H30t. PH - kalnu 0.400 pH of initial solution: 25 tx (Question 1 continues on next page) +X Х Х x=0.00281511476 0400-X 12 = 10-47 -

don 1 - Continued) Vhat is tr GELO un +2 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? 14-47 93 10.5 PH= 2.55< ! So ne need to ado! MooH of preparing the butter CH₃ Coul & NaOH - CHACOONG + 420 0400 me 14:16 X10 ph-1849 -0. 4.00 Buod 3400 CH3COO + H2O 2 CH3COOH + QH 0.000 0. Which will be added? (circle one) NaOH of HCI What volume will be added? D D to 40 PH=9151 10.50 er 2.0 tx PO-X f. Draw the chemical reaction (using structures) that takes place between the NaOH or HCl (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 (8 pts) + H Hid Foto 20-44 H H-G-H - C-323 + H H triot Prres ? 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. (8 pts)