What combination of substances will give a buffered solution that has a pH of 5.05? Assume each pair of substances is dissolved in 5.0 L of water. (K_b for NH₃ = 1.8 × 10^-5; K_b for C₅H₅N = 1.7 × 10^-9) A) 1.0 mol C₅H₅N and 1.5 mol C₅H₅NHCl B) 1.0 mol NH₃ and 1.5 mol NH₄Cl C) 1.5 mol NH₃ and 1.0 mol NH₄Cl D) 1.5 mol C₅H₅N and 1.0 mol C₅H₅NHCl E) none of these

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Quizplus · Accepted Answer

The pH of a buffer solution is determined by the Henderson-Hasselbalch equation. For a buffer with pH 5.05, the pKa should be close to 5.05. The pKa of C5H5NH+ (the conjugate acid of C5H5N) is approximately 5.23, which is close to 5.05, making option A the best choice.

What Combination of Substances Will Give a Buffered Solution That