Determine the pH of an HF solution of each of the following concentrations?
1. 0.300 M
2. 5.10×10^−2 M
3. 2.60×10^−2 M
In which cases can you not make the simplifying assumption that x is small?
Ka of HF = 3.5*10^-4
Please, please help!!!!
HF is a weak acid so you will have to make an ICE table
HF + H2O —-> H3O+ + F-
x^2/(0.300-x) = 3.5×10^-4
Assume 0.300-x ~ 0.300
-log[X] to find pH
if x / 0.300 is less than 5%, then your assumption is good. Otherwise, you cannot assume x is small and you will have to solve the quadratic equation.
This will get you going on how to solve the questions.
Ph Of Hf
—equation from forming ice table
-log.010073 = 1.99684
in b and c you cant make that assumption because the actual concentrations produced are more than 5% that the error allows for when using the small number approximation
would you happen to know how to do the buffers in medicine problem??
pH= -log[5.10 x 10^-2]= 1.29
pH= -log[2.60 x 10^-2]= 1.59
pH=-log[3.5 x 10^-4]= 3.46
These are all acidic because they are under 7. Anything above 7 is basic.
x is smallest in the first one.