Typically the concentration of hydronium, H3O+, or hydroxide, OH, ions in an aqu
ID: 546962 • Letter: T
Question
Typically the concentration of hydronium, H3O+, or hydroxide, OH, ions in an aqueous solution is less than 1 M. It is not uncommon to have hydronium ion concentrations that are much smaller, such as 2.60×105. pH, therefore, is a convenient way to restate the hydronium concentration. pH is equal to the negative log of a hydronium ion concentration in solution:
pH=log[H3O+]
Access the pH calculation simulation, which will open in a new window. Edit the concentration by typing a value between 1.0×107 and 1.8×101 into the space provided. Select a compound from the dropdown menu and click Dip. The pH value will display in the History field.
Part C
Use the data in the simulation to find the Ka value of HF, hydrofluoric acid.
Express your answer to two significant figures.
Explanation / Answer
c)
find Ka fo rHF
Ka = [H+][F-]/[HF]
once you get pH, and initial concentration of acid, M...
[H+] = 10^-pH
[F-] = [H+] due to stoichiometry
[HF]in equilbirium = M - 10^-pH
then
Ka = (10^-pH)(10^-pH) / ( M - 10^-pH)
Ka = (10^-2pH) / ( M - 10^-pH)
the actual vlaue of Ka is
Ka = 7.2*10^-4
therefore, you msut get a value near that
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