You have been hired by a company that is working to generate fuel from bacteria
ID: 965036 • Letter: Y
Question
You have been hired by a company that is working to generate fuel from bacteria that consume organic waste products. The bacteria must be grown in a medium with a pH similar to that of the environment that wil be functioning in. This particular bacteria thrives in an acidic environment, so you decide to make a buffer of pH2. If you have 100.0 mL of a .05M H3PO4 solution available, how many grams of NaH2PO4 (137.99 g/mol) must you add to create this buffer? The Ka of this conjugate pair is 7.1 * 10^-3
Explanation / Answer
pH = 2
millimoles of H3PO4 = 100 x 0.05 = 5
pKa = -log Ka = -log (7.1 * 10^-3) = 2.15
pH = pKa + log [NaH2PO4 / H3PO4]
2 = 2.15 + log [NaH2PO4 / 5]
[NaH2PO4] = 3.54
millimoles of NaH2PO4 = 3.54
moles = 3.54 x 10^-3
mass of NaH2PO4 = moles x molar mass = 3.54 x 10^-3 x 137.99
mass of NaH2PO4 = 0.488 g
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.