In titration of a 0.10M soln of Na2Co3 with HCL which of the following will be present in the largest concentration at the first equivalence point?
a. Co3^2-
b. HCO3-
c. H+
d. H2CO3
e. OH-
You must recognize what is going on here.
CO3^-2 + H^- ==> HCO3^- + H2O . When the indicator turns at the first equivalence point, this is the reaction that has taken place. Technically, the highest concn will be water; however, that isn't one of the answers. After looking at the equation, you say.......
To determine which species will be present in the largest concentration at the first equivalence point, we need to consider the reaction that takes place between Na2CO3 and HCl during titration.
The balanced equation for the reaction is as follows:
Na2CO3 + 2HCl -> 2NaCl + H2O + CO2
At the first equivalence point, all the Na2CO3 will be neutralized by HCl, and the moles of HCl used will be equal to the moles of Na2CO3 initially present.
Now let's look at each of the options provided:
a. CO3^2-: Carbonate ion. At the first equivalence point, all the carbonate ions will be converted to bicarbonate ions (HCO3-) by reacting with one mole of HCl. Therefore, the concentration of CO3^2- will not be the largest at this point.
b. HCO3-: Bicarbonate ion. At the first equivalence point, bicarbonate ions will be present because they are formed by the reaction between Na2CO3 and HCl. Since all of the Na2CO3 will be converted to HCO3-, the concentration of HCO3- will be the largest at the first equivalence point.
c. H+: Hydrogen ion. Hydrogen ions are formed when HCl is dissolved in water. However, at the first equivalence point, all the HCl would have reacted with Na2CO3, leaving no HCl or excess H+ ions in the solution. Therefore, the concentration of H+ ions will not be the largest at this point.
d. H2CO3: Carbonic acid. Carbonic acid is formed from the reaction between HCO3- and H+ ions. However, at the first equivalence point, there will be no excess H+ ions, so the concentration of H2CO3 will not be the largest.
e. OH-: Hydroxide ion. Hydroxide ions are not involved in the reaction between Na2CO3 and HCl. Therefore, the concentration of OH- ions will not be the largest at the first equivalence point.
Based on the analysis, the correct answer is b. HCO3-. The concentration of HCO3- will be the largest at the first equivalence point during the titration of Na2CO3 with HCl.