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Conjugate Acid-Base Pairs

 

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

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