The first two sheets are the report, and hopefully the answers I found are corre

Question

The first two sheets are the report, and hopefully the answers I found are correct. I need help with the third report sheet. I cant figure out the answers to any of the questions. I dont even know where to start, so explanations are totally appreciated with the answers. thanx in advance !!!!

Partner S name: 1 Tria Second Equivalence Point Trial 2 go50M o Concentration of NaOH (M) Volume of Cola (mL) 40 mL NaOH volume added immediately before the large pH increase for the second equivalent (mL) NaOH volume added immediately after the large pH increase for thesecond equivalent (ml Volume of NaOH at the second equivalence point (mL Lll mL 2.5 mL Moles of NaOH at second equivalence point (mol) O. 000 SS tasS Moles of Phosphoric acid from second equivalence point mo Volume of NaOH at 1Vi equivalence point (mL) 5.5 Co ZS pH (pKa2) at 1 first equivalence point Ka2 Concentration of Phosphoric acid in Cola (M) 1.20 x 10-2. From second equivalence point oog4 M Average Concentration of Phosphoric Acid (M) 1. Look up the values for the Ka for Phosphoric acid. List them here: Kal 4320-13 73

Explanation / Answer

Percent error

pKa1 average from experiment = (2.34 + 2.29)/2 = 2.315

percent error pKa1 = (2.315-2.16) x 100/2.16 = 7.1%

pKa2 from experiment = (3 + 2.42)/2 = 2.71

percent error pKa2 = (7.2 - 2.71) x 100/7.2 = 62.36%

The large percent error in case of pKa2 could be due to incorrect volume addition of NaOH to the cola solution.

Carbonated beverage cola,

6 Oz = 29.5735 ml

concentration of H3PO4 from second table = 0.05 M x 0.00425 L/0.04 L = 0.0053125 M

So concentration of H3PO4 in 29.5735 ml would be = 0.00393 M

Phosphorous content = 0.00393 M x 29.5735 ml x 31 g/mol = 3.601 mg

The cola used for the experiment has to be flat, otherwise the CO2 content would add upto the basicity of the cola and we would require lesser amount of NaOH for the neutralisation of remaining H3PO4 in cola solution.

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