Explanation:
The reaction equation will be as follows.
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 ![[H_{2}AsO^{-}_{4}]](https://tex.z-dn.net/?f=%5BH_%7B2%7DAsO%5E%7B-%7D_%7B4%7D%5D)
and ![[H^{+}]](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%5D)
is x.
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)
= 
= 1.958
Thus, we can conclude that the pH of a 0.500 M solution of arsenic acid is 1.958.
Test tubes, flasks, bunsen burners, random chemical equations
Complete Question:
A chemist prepares a solution of iron chloride by measuring out 0.10 g of FeCl2 into a 50. mL volumetric flask and filling to the mark with distilled water. Calculate the molarity of anions in the chemist's solution.
Answer:
[Fe+] = 0.0156 M
[Cl-] = 0.0316 M
Explanation:
The molar mass of iron chloride is 126.75 g/mol, thus, the number of moles presented in 0.10 g of it is:
n = mass/molar mass
n = 0.10/126.75
n = 7.89x10⁻⁴ mol
In a solution, it will dissociate to form:
FeCl2 -> Fe+ + 2Cl-
So, the stoichiometry is 1:1:2, and the number of moles of the ions formed are:
nFe+ = 7.89x10⁻⁴ mol
nCl- = 2*7.89x10⁻⁴ = 1.58x10⁻³ mol
The molarity is the number of moles divided by the solution volume, in L (50.0 mL = 0.05 L):
[Fe+] = 7.89x10⁻⁴/0.05 = 0.0156 M
[Cl-] = 1.58x10⁻³/0.05 = 0.0316 M
