Answer:
is dissociation constant and the value of
is 4.98.
Explanation:
The pH of the solution = 2.95 M
![pH=-\log[H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%5BH%5E%2B%5D)
![2.95=-\log[H^+]](https://tex.z-dn.net/?f=2.95%3D-%5Clog%5BH%5E%2B%5D)
..[1]
Concentration of unknown monoprotic acid = C = 0.1224 M

Initially
C 0 0
At equilibrium
(C-x) x x
The expression of a dissociation reaction can be written as;
![K_a=\frac{[A^-][H^+]}{[HA]}](https://tex.z-dn.net/?f=K_a%3D%5Cfrac%7B%5BA%5E-%5D%5BH%5E%2B%5D%7D%7B%5BHA%5D%7D)

( from [1])


The value of
:
![pK_a=-\log[K_a]](https://tex.z-dn.net/?f=pK_a%3D-%5Clog%5BK_a%5D)
![=-\log[1.038\times 10^{-5}]=4.98](https://tex.z-dn.net/?f=%3D-%5Clog%5B1.038%5Ctimes%2010%5E%7B-5%7D%5D%3D4.98)
is dissociation constant and the value of
is 4.98.
The group 7A elements are called Halogens.
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The answer is C!!!!!!!!!!!!!!!!!!!