Respuesta :
2. The pH scale is well used in Chemistry to determine if a solution will be considered to be acidic or basic, and this definition is due to the concentration of protons, which you can also see as H+, and Hydroxide ions, which is also OH-, for concentration, it is usually represented with this symbol []. Now to find out what is the pH of a substance, we can use the pH formula, which is:
pH = -log [H+]
For example we have in question number 1
pH = -log [1*10^-8]
pH = 8
Therefore it will be a basic compound, because the pH scale is divided into below 7 and over 7, <7 = acidic, which also means a high concentration of H+.
>7 = basic, which also means a low concentration of H+
But if we make this simple calculation 7+7 we will have 14, which is the higher number from the pH scale, and this thought when it comes to concentration of ions will be describe as:
1*10^-14 = (1*10^-7) * (1*10^-7)
This is also represented by this equation:
Kw = [H+] * [OH-], where Kw is the constant for pure water
So from this math you realize that if we increase H+, we need to decrease OH-, the same goes for OH-, this is why substances are basic or acids
Now into our question
2. A) if the solution has a concentration of H+ = 1*10^-4, this means that the pH is 4, and 14 (higher value) - 4 = 10, therefore the concentration of OH- must be really low, which is 1*10^-10, or simply 10
B) If the solution has a [H+] = 1*10^-4, the pH will be 4, therefore the solution will be acidic