Hi sorry i dont know this i know alot about science but i dont know this
Answer: a)
and pH = 1.04
b)
and 
c)
and ![[OH^-]=1.41\times 10^{-4}](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D1.41%5Ctimes%2010%5E%7B-4%7D)
Explanation:
pH or pOH is the measure of acidity or alkalinity of a solution.
pH is calculated by taking negative logarithm of hydrogen ion concentration.
![pH=-\log [H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5BH%5E%2B%5D)
![pOH=-\log [OH^-]](https://tex.z-dn.net/?f=pOH%3D-%5Clog%20%5BOH%5E-%5D)

a) ![[H^+]=0.090M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D0.090M)
![pH=-\log [0.090]=1.04](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5B0.090%5D%3D1.04)

![12.96=-log[OH^-]](https://tex.z-dn.net/?f=12.96%3D-log%5BOH%5E-%5D)
![[OH^-]=1.09\times 10^{-13}](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D1.09%5Ctimes%2010%5E%7B-13%7D)
b) ![[OH^-]=0.00098M](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D0.00098M)
![pOH=-\log [0.00098]=3.01](https://tex.z-dn.net/?f=pOH%3D-%5Clog%20%5B0.00098%5D%3D3.01)

![10.99=-log[H^+]](https://tex.z-dn.net/?f=10.99%3D-log%5BH%5E%2B%5D)
![[H^+]=1.02\times 10^{-11}](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D1.02%5Ctimes%2010%5E%7B-11%7D)
c) 
![10.15=-\log [H^+]](https://tex.z-dn.net/?f=10.15%3D-%5Clog%20%5BH%5E%2B%5D)
![[H^+]=7.08\times 10^{-11}](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D7.08%5Ctimes%2010%5E%7B-11%7D)

![3.85=-log[OH^-]](https://tex.z-dn.net/?f=3.85%3D-log%5BOH%5E-%5D)
![[OH^-]=1.41\times 10^{-4}](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D1.41%5Ctimes%2010%5E%7B-4%7D)
Answer:
89.4%
Explanation:
Initially, there is 5.0 of the acetanilide in 100 mL of water, then the solution is chilled at 0ºC. The solubility represents the amount that the solvent (water) can dissolve of the solute (acetanilide). So, at 0ºC, 100 mL of water can dissolve till 0.53 g of the compound, the rest will precipitate and will be recovered.
So, the mass that is recovered is 5.0 - 0.53 = 4.47 g
The percent recovery is:
(4.47/5)x100% = 89.4%
The one with the highest pH would be a solution with 100 mL of water and also 20 mL of 0.1 M NaOH is added. Solutions without buffers would have the highest pH since the resistance to change is very low. Hope this answers the question.