Answer:
3.9.
Step-by-step explanation:
(Molar mass of 342.15 g/mol).
The first thing to do in this question is to coverts our units. We are given 6.70 lb = 453.592 × 6.70 lb = 3039.0664 g of aluminum sulfate.
2050 gallons of water = 2050 × 3.785 = 7759.25 Litres.
After this we will now look for the Concentration aluminum sulfate using the formula below:
Concentration = number of moles ÷ volume. ------------------------------------(1).
Recall; Number of moles = 3039.0664/ 342.15 = 8.8823 moles. The volume = 2050 gallons = 7759.25 Litres.
Therefore, slotting in the values of of number of moles and volume into the equation (1) above, we have;
Concentration= 8.8823 moles/ 7759.25 Litres. = 0.001145 M.
The next equation we are going to make use of today is that of the solubilty product that is;
Ksp = (Al^3+) (OH^-)^3.
So, we have the ksp = 1.3 × 10^-33 and the value of (Al^3+)= 0.001145 M.
Hence, making (OH^-) the subject of the formula;
(OH^-) = ( 1.3 × 10^-33 / 0.001145)^1/3.
(OH^-) = 8 × 10^-11 M.
Hence, pOH = - log (OH^-)
pOH = - log (8 × 10^-11).
pOH = 10.1
Therefore, the values of pH is; 1
pH + pOH = 14.
pH = 14 - 10.1 = 3.9.