Acid-Base Titration, Determination of Carbonate and Bicarbonate in a water sample
The purpose of this lab is to determine the concentration of two bases, carbonate and bicarbonate, by using a potentiometric titration. We can determine the concentration of the bases in the reactions ( H+ +CO3- < ==> HCO3- and H+ + HCO3- < ==> H2CO3-) by the way the pH of the solution changes. The way the pH changes when a strong acid is added can be used to determine the concentration of the strong and weak bases that are present in the solution. We can determine this by knowing that when a acid is added to a solution the majority of the hydrogen ion will react with the strongest base. In this experiment the majority of the hydrogen ion will react with the carbonate ion and convert it to the bicarbonate ion.
Carbonate and Bicarbonate Titration Curve
The total Alkalinity in this experiment is expressed by total moles of base present per liter of solution. In this labe experiment the total amount of base present is equal to the moles of acid needed to reduce the pH of the solution to 4.3.Using my data I found that the total alkalinity to be 2.6 moles of base per liter of solution.
Determination of Carbonate and Bicarbonate Concentrations
By using the titration curve I decided that there is both carbonate and bicarbonate in the initial solution because of the amount of acid needed to get to the second equivalent point is double what it took to get to the first equivalent point. The concentration of the carbonate in the initial solution is 0.85 moles per liter, and the concentration of the bicarbonate in the initial solution is 0.9 moles per liter.
When a carbonate is the only base stronger than water in a solution the pH is greater than 8.3 and when doing a potentiometric titration the amount of acid needed to reduce the pH from its initial value to 8.3 is... [continues]
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