Write down three methods you could use to prepare a H2PO4- / HPO4^2- buffer. In

Question

Write down three methods you could use to prepare a H2PO4- / HPO4^2- buffer. In each case give the chemical formulas of the compounds you would mix and identify a limiting reactant if there is one.
Im pretty sure she wants me to use these: HCl, NaOh, NaC2H3O2 (s), 3H2O, NH4Cl, NaH2PO4, NaHPO4 Write down three methods you could use to prepare a H2PO4- / HPO4^2- buffer. In each case give the chemical formulas of the compounds you would mix and identify a limiting reactant if there is one.
Im pretty sure she wants me to use these: HCl, NaOh, NaC2H3O2 (s), 3H2O, NH4Cl, NaH2PO4, NaHPO4
Im pretty sure she wants me to use these: HCl, NaOh, NaC2H3O2 (s), 3H2O, NH4Cl, NaH2PO4, NaHPO4

Explanation / Answer

Fpr a H2PO4- and HPO4-2 buffer

we need:

a salt that will yield H2PO4- = Na2HPO4

a salt which yields HPO4- = NaH2PO4

so

in water, add:

mass of NaH2PO4 and Na2HPO4

There are no "limiting reactants" we will add as we need to adjunt pH

from

pH = pKa + log(HPO4-2 / H2PO4-)

MOLECULAR EQUATIONS

Na2HPO4(aq) ---> 2Na+(aq) + HPO4-2

NaH2PO4(aq) ---> Na+(aq) + H2PO4-

then

There is buffer formation, since HPO4-2 is the conjugate base of the acid H2PO4-

H2PO4- <---> H+ + HPO4-2

note that if we add OH- (bases) then:

H+ + OH- --> H2O

if we add H+ acids, then the shift goes toward

HPO4-2 + H+ ---> H2PO4-

then, you can see how th buffer will avoid drastic pH changes, due to H+ control

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.