Question

which component of a buffer composed of H7

Identify where we are in the titration of a 24.0 mL of 0.15 M carbonic acid, H2CO3 with the addition of 18.0 mL of 0.20 M NaOH? o at the first equivalence point o at the second 1/2 equivalence point O at the second equivalence point O at the first 1/2 equivalence point after the second equivalence point D Question 25 3 pts Which of the following best describes the pH at the equivalence point in the titration of HC3H$Os with NaOH? o acidic due to the presence of HC,H,O. O basic due to the presence of CH:0:1 o acidic due to the presence of H10 basic due to the presence of OH-

Answer 1

Q24 mili moles of [OH^-] ions = molaraity * volume

= .20(M)* 18(mL)

= 3.6 milimoles

similarly milimoles of [H⁺] from  H₂CO₃= 24(mL)*0.15(M)

= 3.6 milimoles but this the concentration of first [H⁺] ions i.e H₂CO₃ is diprotic acid so in first stage one [H⁺] ion is formed and its milimoles is 3.6 so it will react with present milimoles of NaOH reaching at the first equivalence point(assuming there is complete dissociation H₂CO₃)

H2CO3 = H+ + HCO3 HCO3 = H+ + CO3-

Q25 HC₃H₅O₃ is the  lactic acid with dissociation as follows

о ОН ОН с- -С- -СН3 C -С- -CH3 + н* НО H н lactic acid lactate hydrogen ion

so the solution is basic as there is stong base weak acid and du to present of more [OH^-] ion as the sodium will form good electrolyte with lactate shifting the above equlibrium to left which reduces the concentration of hydrogen ion and make the solution basic

Hence the answer is D