For the titration of a weak acid with a strong base what is the pka of the weak acid if the ph is 6.72 at the equilvalence point (100% t), 9.12 at the end point, and 4.23 at 50% t? answer with one sig fig.

Explanation:

We have to calculate value.

It is known that at the equivalence point concentration of acid is equal to the concentration of anion formed.

Hence,         [HA] =

Now, relation between and pH is as follows.

                   pH =

Putting the values into the above formula as follows.

                   pH =

                  4.23 =            (as [HA] = )

                    = 4.23                (as log (1) = 0)

or,                   = 4

Thus, we can conclude that of given weak acid is 4.  

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.