The values you calculate for this Prelab Exercise are required for your experime
ID: 492846 • Letter: T
Question
The values you calculate for this Prelab Exercise are required for your experiment. Determine the [H_3O^+] of the eight buffer solutions made 1.10 M acetic acid and of by mixing 900 M Sodium acetate solutions according to the following volumes. The pK_a for acetic acid, CH_3COOH is 4.745. Show a detailed calculation for one of the solutions. Determine the following showing your work: The [H_3O^+], in M, of 10.00 mL of 10.00 mL of 0.100 M NaOH after adding 10.00 mL of indicator solution. The [H_3O^+], in M, of 10.00 mL of 0.100 M HCl after adding 10.00 mL of the indicator solution.Explanation / Answer
Q1.
find [H3O+] of each buffer...
assume mix is [HA] = 1.1 M and [A-] = 0.9 M and pKa = 4.75
recall that:
From buffer equation ( Henderson HAsselbach equation)
we get
pH = pKa + log(A-/HA)
where pKa is the -log(X) value of Ka, 4.75 for acetic acid
A- is the molar concentration of the acetate
HA is the molar concentration of the acid
so
mmol of acid = MacidVacid
mmol of acetate= MacetateVacetate
note that if A- > HA, then pH > 4.75
if HA >A- , then pH < 4.75
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Solution Vacid Vacetate mmol of acid mmol of acetate ratio (acetate/acid) log(ratio) pH = pKa + log(ratio) [H3O+] = 10^-pH 1 8 2 8.8 2.2 4.00 0.60 5.35 4.45E-06 2 7 3 7.7 3.3 2.33 0.37 5.12 7.62E-06 3 6 4 6.6 4.4 1.50 0.18 4.93 1.19E-05 4 5 5 5.5 5.5 1.00 0.00 4.75 1.78E-05 5 4 6 4.4 6.6 0.67 -0.18 4.57 2.67E-05 6 3 7 3.3 7.7 0.43 -0.37 4.38 4.15E-05 7 2 8 2.2 8.8 0.25 -0.60 4.15 7.11E-05 8 1 9 1.1 9.9 0.11 -0.95 3.80 1.60E-04Related Questions
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