# Chemistry lab report - acid, base, pH, buffers

Feb 3rd, 2012
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This is a 13-page Chemistry lab report - acid, base, pH, buffers

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IntroductionBuffer solutions contain both a weak acid and its conjugate weak base in appreciable concentrations. Within limits, these solutions tend to resist changes in pH upon addition of either H3O+ or OH-. In buffer systems like NaC2H3O2-HC2H3O2 mixtures, the principal source of the acetic acid molecule is from the acid; the principal source of the acetate ion is from the salt. Therefore, the [H3O+] is determined by the salt/acid (or equivalently, the base/acid) mole ratio. For a conjugate acid/base pair: pH = pKa + log10 [conjugate base] / [acid]pKa = 4.74. The Henderson-Hesselbalch equation is used to find the pH of a buffer solution: pH = pKa + log ([A-] / [HA]) ,Where pKa is an experimentally found constant for the acid HA, [HA] is the concentration of the acid, and [A-] is the concentration of the conjugate base. AnalysisFinal Experiment ValuesBuffer 1 - Titration with 0.025 M NaOHCH3COONa - 0.147 gTrial 1 Trial 2Volume Initial - 20 mL 20 mLVolume Final - 31 mL 29.8 mLTotal Volume of Titrant - 11 mL 9.8 mLMoles Titrant: moles = M x V = 0.025 M x 0.011 L = 0.000275 moles 0.000245 molesInitial pH - 4.77

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