16.e Due: Thursday 11/16/2017 (Last Day of class) Part 4: Polyprotic acids (Answ

Question

16.e

Due: Thursday 11/16/2017 (Last Day of class) Part 4: Polyprotic acids (Answer all questions in this section) 16. As you know carbonic acid, H COs, is of co ncern in the lab because it is one of the species that forms when CO2 is absorbed into water carbonic acid, H CO, has (give a number) acid dissociation equilibriums p) Write these equilibriums as acid dissociation reaction and give the equilibrium expression (4 pts) Write these equilibriums as base association reaction and give the equilibrium expression (4 pts) (1 pt) d. If we assume that we have pure water what would be the expected pH? (I pt) f. Now solve for the actual pH, the pOH, and the fraction of your principle species in the system at this pH based on the system you have defined above if the initial concentration of H CO, is (5 pts) 4 x 103 M 91 Page

Explanation / Answer

16e) pH for pure water=7

pka for H2CO3/CO32- system=6.35

pka for H2CO3/HCO3- system=10.33

As pka (H2CO3/CO32-)<pH ,so H2CO3 deprotonate at this pH to yield CO32- or carbonate

As pka for H2CO3/HCO3- system=10.33> pH so H2CO3 does not deprotonate at this pH to yield HCO3- or bicarbonate

So ,the principle species at pH 7 is CO32- or carbonate

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