During the dark ages-All that wasn't around the christian religion were lost. Knowledge and discoveries before the Dark Ages were mainly in Greek ideas. Biblic scripts however were in Latin. Therefore all inventions up to the dark ages were lost and only religious scripts preserved in the churches. Outside the church, no one knew how to write, read or even communicate.
Hmm, friction maybe? I guess it depends on how fast she stopped?
Explanation:
The reaction equation will be as follows.
![H_{3}AsO_{4} \rightleftharpoons H_{2}AsO^{-}_{4} + H^{+}](https://tex.z-dn.net/?f=H_%7B3%7DAsO_%7B4%7D%20%5Crightleftharpoons%20H_%7B2%7DAsO%5E%7B-%7D_%7B4%7D%20%2B%20H%5E%7B%2B%7D)
Hence, the expression for
is as follows.
![K_{a} = \frac{[H_{2}SO^{-}_{4}][H^{+}]}{[H_{3}AsO_{4}]}](https://tex.z-dn.net/?f=K_%7Ba%7D%20%3D%20%5Cfrac%7B%5BH_%7B2%7DSO%5E%7B-%7D_%7B4%7D%5D%5BH%5E%7B%2B%7D%5D%7D%7B%5BH_%7B3%7DAsO_%7B4%7D%5D%7D)
Let us assume that the concentration of both
and
is x.
![2.5 \times 10^{-4} = \frac{x \times x}{0.5}](https://tex.z-dn.net/?f=2.5%20%5Ctimes%2010%5E%7B-4%7D%20%3D%20%5Cfrac%7Bx%20%5Ctimes%20x%7D%7B0.5%7D)
x = 0.01118034
This means that the concentration of
is 0.01118034.
Since, we know that the relation between pH and concentration of hydrogen ions is as follows.
pH = ![-log [H^{+}]](https://tex.z-dn.net/?f=-log%20%5BH%5E%7B%2B%7D%5D)
= ![-log (0.01118034)](https://tex.z-dn.net/?f=-log%20%280.01118034%29)
= 1.958
Thus, we can conclude that the pH of a 0.500 M solution of arsenic acid is 1.958.