phosphoric acid being titrated with unknown NaOH concentration

14.25 mL of NaOH used to titrate to a pH of 11.61

phosphoric acid concentration=250mM

phosphoric acid volume=25.00mL

pka1=2.15

pka2=6.80

pka3=12.37

only do Question 7, disregard previous ones.

(c) Use the logic you applied in question 1 to determine the mmoles of NaOH required to titrate from the first to the second equivalence point. Show your logic. (d) For the titration of the 250mM phosphoric acid, state the mL volume of NaOH required to titrate from the first equivalence point to the second. Do this for both titrations and then calculate the average volume. (e) With information you provided above, calculate the concentration of the NaOH titrant. (show your calculations). 7. There are many ways for making a phosphate buffer. Depending on what is available in the lab, a phosphate buffer can be made from: (i) Phosphoric acid and a strong base, e.g. H3PO4/NaOH (ii) A phosphate salt and the addition of either a strong acid or base, e.g. NaH2PO4/NaOH (iii) The phosphate salt of both the conjugate acid and the conjugate base, e.g. NaH2PO4/Na2HPO4 (iv) Or a combination of the reagents mentioned above More often, we start with a solution of the salt form and then titrate with either a strong base or acid to obtain the pH that we desire. Determine the expected pH and the buffer concentration of the following solutions (Use the Henderson-Hasselbalch equation and the pKa values as presented in the introduction to help you and show your reasoning and calculations). Provide answers with 3 significant digits. (a) 8.16g of NaH2PO4(MW120g/mol ), 5.00ml of 6.00MNaOH and enough water to make a final volume of 400mL (b) 11.36g of Na2HPO4 (MW 142g/mol ), 15ml of 4.0MHCl and enough water to make a final volume of 500ml. (c) 21.6mL of 2.50MH3PO4,12.3mL of 6.00MNaOH and 266.1mL of water