Diprotic Acid pH Titration Lab PDF

Lab: Diprotic Acid pH Titration Here is guide to the calculations you need for finding the molar mass of your chosen diprotic acid. ***PLEASE READ CAREFULLY*** Prior to calculating the molar mass of your unknown diprotic acid, you must first identify your pKa values (pKa1 and pKa2) for each trial b...

Lab: Diprotic Acid pH Titration Here is guide to the calculations you need for finding the molar mass of your chosen diprotic acid. ***PLEASE READ CAREFULLY*** Prior to calculating the molar mass of your unknown diprotic acid, you must first identify your pKa values (pKa1 and pKa2) for each trial based on titration curves. Below is a helpful picture on where to identify your pKa values. The first midpoint pH = pKa1 The second midpoint pH = pKa2 After you have determined your pKa values for each trial, you must determine the volume of NaOH at the 2nd equivalence point (LOOK AT YOUR GRAPHS) since this is crucial when calculating your molar mass. Once you have determined your volume of NaOH at the 2nd equivalence point, you are ready to calculate the molar mass of your chosen diprotic acid: 1. FIRST, find the moles of NaOH at the 2nd equivalence point 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁𝑎𝑂𝐻 = 𝑁𝑎𝑂𝐻 𝑠𝑡𝑜𝑐𝑘 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑣𝑜𝑙. 𝑜𝑓 𝑁𝑎𝑂𝐻 𝑎𝑡 2𝑛𝑑 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑐𝑒 𝑝𝑡 2. SECOND, find the moles of the diprotic acid  1 𝑚𝑜𝑙 𝐻2 𝐴 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑎𝑐𝑖𝑑 = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁𝑎𝑂𝐻 × 2 𝑚𝑜𝑙 𝑁𝑎𝑂𝐻 3. LASTLY, find the molar mass of your chosen diprotic acid 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑎𝑐𝑖𝑑 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑 (𝑔) 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑎𝑐𝑖𝑑 = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑎𝑐𝑖𝑑 (𝑚𝑜𝑙) Once you have determined the molar mass of your diprotic acid for each trial, take the AVERAGE, the STANDARD DEVIATION, and the % ERROR. List out the possible identity of the unknown acid based on your molar mass from the trials and choose the one that is relatively close to it. Finally, write out the balanced chemical equation for the reaction of your chosen diprotic acid with NaOH.