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Which of the following species would form a buffer with HPO₄²⁻?

a) NaOH
b) H₂SO₄
c) Na₂HPO₄
d) KOH

User Sofya
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1 Answer

7 votes

Final answer:

Na₂HPO₄ will form a buffer with HPO₄²⁻ because it will provide the corresponding conjugate acid when dissolved in water, which is necessary for a buffer solution. So, the correct option is C.

Step-by-step explanation:

A buffer solution contains a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid. This allows the buffer to resist changes in pH when small amounts of acid or base are added. HPO42- is the conjugate base of the weak acid H2PO4-. To form a buffer with HPO42-, we need to add either the weak acid H2PO4- itself, or a salt containing the H2PO4- ion.

Looking at the options provided:

  • NaOH is a strong base and does not provide the necessary conjugate acid.
  • H2SO4 is a strong acid and would react completely with HPO42- rather than form a buffer.
  • Na2HPO4 contains the HPO42- ion and would provide the corresponding conjugate acid H2PO4- when dissolved in water, making it the correct choice.
  • KOH is also a strong base and, like NaOH, does not provide the conjugate acid.

Therefore, the correct answer is (c) Na2HPO4, as it will combine with HPO42- to create a buffer solution.

User Justin Warkentin
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