Conjugate Acid-Base Pairs

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Page ID: 221932

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Chemical Concept Demonstrated

Strengths of acids and their conjugate bases

Demonstration and Explanations

1. Compare HCl, HOAc, NaCl, and NaOAc: HCl is a stronger acid than HOAc. NaCl is a weaker base than NaOAc. Stronger acids have weaker conjugate bases.

HCl	+	NaOAc	--->	HOAc	+	NaCl
stronger acid		stronger base		weaker conjugate acid		weaker conjugate base

2. Compare HCl, NaOH, and NaCl: HCl is a stronger acid than water. NaCl is a weaker base than NaOH. Strong acids react with strong bases to form weaker acids and bases.

HCl	+	NaOH	--->	H₂O	+	NaCl
stronger acid		stronger base		weaker conjugate acid		weaker conjugate base

3. Compare NaOH, NH₃, and H₂O, and NH₄Cl: NaOH is a stronger base than NH₃. Water is a weaker acid than NH₄Cl. Weaker bases have stronger conjugate acids. NH₃ is a weak base, but its conjugate acid, NH₄Cl, is a strong acid.

NH₄Cl	+	NaOH	--->	H₂O	+	NH₃
stronger acid		stronger base		weaker conjugate acid		weaker conjugate base

Contributors

Dr. George Bodner (Perdue University)