Abstract: Our method for determining the unknown weak acid was to determine the equilibrium constant K from the molecular weight of the weak acid from our titration data. In this lab the acid Potassium hydrogen phthalate and two unknown acids were titrated. We determined the molar mass of the Potassium hydrogen phthalate, for the unknown acids we calculated the molar mass and the Ka values. We used NaOH as the known base for titrating in all three of the titrations. Our ka value based on our titration curve of KHP was 6.9 (the equivalence point where the pH equals the pKa) and our unknown acids were determined to be Hexanoic Acid (with an actual molar mass of 116.6g) with a determined mass of 116.1g. The unknown A3 acid turned out to be 2-oxyglutaric Acid with a determined molar mass of 146g/mol (and an actual molar mass of 147.15g/mol).
Introduction: Titration is a general class of experiment where a known property of one solution is used to infer an unknown property of another solution. In acid-base chemistry, we often use titration to determine the pH of a certain solution. By investigating a weak acid titration curve we learned more about the balances involved in equilibrium. The titration curve allows us to see pH versus volume of added titrant, our titrant being a strong base (NaOH). Our plan for the first week was to standardize the sodium hydroxide solution by determining the equivalence point (total moles of HA present=the total moles of base added). We then will perform a weak acid titration with and without a pH meter. We then plotted our titration curve and determined the Ka of the weak acid. At the point of the graph in which the slope of the line is almost vertical the middle of that range is the equivalence point. In this lab we started with the KHP sample and titrated three different trials that were within 1% difference in the ratio of mol NaOH: mol KHP, having this kind of values shows our precision in the titration... [continues]
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