occ CHM 122 WEEK 8: Generating a Titration Curve to Determine K, for an Acid PRE
ID: 1025145 • Letter: O
Question
occ CHM 122 WEEK 8: Generating a Titration Curve to Determine K, for an Acid PRELAB ASSIGNMENT (modified to replace advance study assignment) Student Consider titration curves given in the lab handout (and repeated here) to answer the questions below: Date Acid 1 1. EP volume (mL) p at E EPu/2 volume (ml) EP1/2 pH pK, Acid 1 Acid 2 Show your work related to determining EP 1/2 volume and pk, Show all your work related to determining K 2. Which acid is the weaker acid, acid 1 or acid 27 How do you know? Give brief reasoning 3. Which sample had more moles of acid in it initially? How do you know? Give brief reasoningExplanation / Answer
Titration plot
1.
pKa = -log[Ka]
EP volume (ml) EP pH 1/2EP pH pKa Ka
Acid 1 35 10.5 8.1 8.1 8 x 10^-9
Acid 2 42 9.0 6.0 6.0 1 x 10^-6
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2. weaker acid is Acid 1 as it has higher initial pH. pH is inversely proportional to [H+] in solution.
3. more moles of acid is present in Acid 2, which has lower pH. pH and [H+] inversely proportional.
4. moles of base = 0.1 M x 30 ml = 3 mmol
mass of acid needed = 3 mmol x molar mass of given acid/1000 = grams of acid
volume of NaOH needed to reach EP = 3 mmol/0.1 M = 30 ml
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