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Grad 5/2018 11:15 AM A91.7/100 4/5/2018 10:54 AM PrintCalculatorPeriodic Table o

ID: 1039590 • Letter: G

Question

Grad 5/2018 11:15 AM A91.7/100 4/5/2018 10:54 AM PrintCalculatorPeriodic Table on 18 of 18 Map What concentrations of acetic acid (pka 4.76) and acetate would be required to prepare a 0 10 M buffer solution at pH 4.97 Note that the concentration and/ar pH value may differ from that in the first question STRATEGY 1. Rearrange the Henderson-Hasselbalch equation to solve for the ratio of base(acetate) to acid (acetic acid), [A 2. Use the mole fraction of acetate to calculate the concentration of acetate. 3. Calculate the concentration of acetic acid. That is, there are 1.4 molecules Step 1: The ratio of base to acid is 1.4. ofacetate for each molecule of Step 2: The mole fraction of acetate is 0.58, and the concentration of acetate is 0.058 Step 3: Calculate the concentration of acetic acid. acetic acid. Number acetie acia]-M ® Gwr Up & View Sciulon 9 Check Answer O Neri ?? Exi Previous Hint acBook A

Explanation / Answer

HA + A- = 0.1 ------------------> 1

pH = pKa + log [A- / HA]

4.9 = 4.76 + log [A- / HA]

log [A- / HA] = 0.14

A- = 1.38 HA -----------------> 2

from 1 and 2

HA + 1.38 HA = 0.1

HA = 0.0420

[acetic acid ] = 0.0420 M

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