Ask Question
28 May, 11:19

What is the ph of a soft drink in which the major buffer ingredients are 6.6 g of nah2po4 and 8.0 g of na2hpo4 per 355 ml of solution?

+2
Answers (1)
  1. 28 May, 14:48
    0
    The Relative Formula Mass of NaH2PO4 is 120 g/mol

    Therefore, the number of moles = 6.6/120

    = 0.055 moles of NaH2PO4 which is also equal to the number of moles of H2PO4.

    [H2PO4-] = Number of moles oof H2PO4-/Volume of the solution in L

    = 0.055 / (355 * 10^-3)

    = 0.155 M

    Na2HPO4 undergoes complete dissociation as follows;

    Na2HPO4 (aq) = 2Na + (aq) + HPO4^2 - (aq)

    1 mole of Na2HPO4 = 142 g/mol

    Therefore; number of moles = 8.0/142

    = 0.0563 moles

    [HPO4 ^-2] is given by no of moles HPO4^2 - / volume of the solution in L

    = 0.0563 / (355*10^-3)

    = 0.1586 M

    Both H2PO4^2 - and HPO4^2 - are weak acids the undergoes partial dissociation

    Ka of H2PO4 - = 6.20 * 10^-8

    [H+] = Ka * ([H2PO4-]/[HPO4 (2-) ]

    = (6.20 * 10^-8) * (0.155/0.1586)

    = 6.059 * 10^-8 M

    pH = - log[H+]

    = - log (6.059*10^-8)

    = 7.218
Know the Answer?
Not Sure About the Answer?
Find an answer to your question ✅ “What is the ph of a soft drink in which the major buffer ingredients are 6.6 g of nah2po4 and 8.0 g of na2hpo4 per 355 ml of solution? ...” in 📘 Chemistry if you're in doubt about the correctness of the answers or there's no answer, then try to use the smart search and find answers to the similar questions.
Search for Other Answers