Which of these pairs of substances in aqueous solution would constitute a buffer?
a. HCl + KCl
b. KHPO4 + K2HPO4
c. KOH + KCl
d. HCl + KOH
Buffers are mixtures of weak acid and a salt of the weak acid OR a weak base with a salt of the weak base.
a
Please correct choice B. KHOP4- + K2HPO4 OR KH2PO4 + K2HPO4
Ok...... guess it's B.
To determine which of the pairs of substances would constitute a buffer in aqueous solution, we need to understand the definition of a buffer.
A buffer is a solution that resists changes in pH when small amounts of acid or base are added to it. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
Now, let's analyze each pair of substances:
a. HCl + KCl: HCl is a strong acid, and KCl is a salt formed by a strong acid and a strong base. This pair does not constitute a buffer because it does not involve a weak acid or a weak base.
b. KHPO4 + K2HPO4: In this pair, KHPO4 is a weak acid (monosodium phosphate) and K2HPO4 is its conjugate base (disodium phosphate). This pair does constitute a buffer because it involves a weak acid and its conjugate base.
c. KOH + KCl: KOH is a strong base, and KCl is a salt formed by a strong acid and a strong base. This pair does not constitute a buffer because it does not involve a weak acid or a weak base.
d. HCl + KOH: HCl is a strong acid, and KOH is a strong base. This pair does not constitute a buffer because it does not involve a weak acid or a weak base.
Based on the analysis above, the only pair that would constitute a buffer is b. KHPO4 + K2HPO4.