Question

Alkalinity Determination and Titration:

Please Help, with questions I answered. Equivalance 1(EP1)= 27.5mL, at 8.25pH ; Equivalance 2(EP2) = 61mL, at 4.28pH

HCl=0.1 M

20mL of unknown solution gathered

Determining the moles of carbonate ion: The first EP is the first protonation of the carbonate ions. HCl = 0.1M Moles of CO;2- = (0.100 M*(0.0275L)/(0.02L)=1.375 M Determining the moles of bicarbonate ion: The second EP is the protonation of bicarbonate ions AND the second protonation of carbonate ions. Moles of HCO3 = (0,061L(0.100M)/(0.02L)-2(1.375M)-0.3 M Use this information and the volume of solution acquired to determine (CO?) and (HCO3) in your sample. 1.375M/0.0200L = 68.75 M CO;2- O3M 0.0200L = 15 M HCO

Answer 1

This is a strong acid (HCl) vs weak base(H2CO3) titration. Firstly,one of the two protons of H2CO3 is lost forming HCO3- ion which is complementary strong. Then the second proton is going to remove by HCl leading to the formation of (CO3)2- ion. So,there will be two steps in this titration method i.e., EP1 and EP2. The gathered solution,the volume in ml of HCl can be experimentally found and when this is plotted against the pH ,we get the exact alkalinity at which the protons are lost. The calculation is attached below-

As, we know. Visi = V2 S2 H₂ coz – H607 60 - 0 0 245 L X 6.4 H = 0,02 L x S2 "= vol. of Hel = 0.0275 L S2 = 0.0275 X0.1 M +0.1375 M S, = stroength of Hel = 0.1M 0.02 V = vol. of unknown sol=0.022 [co3? -] = 0.1375 M = 6.875 M/ S2 = strength of $coz 2 0.02 L Similarly, for EP2. visi = V2 S2 0.061 LXO.1M = 0.02L X S2 S = 0.305 M. [Hoz 1² 0.305 = 15.25 M 0.02