I have 25 million gallons of water at a pH of 6.5. I add 17.4 million gallons of 12.5% by wt sodium hypochlorite (NaClO) at a pH of 12.5 to this water. What will my pH of my final solution be?
It's been about 5 years since I took chemistry and I just don't remember how to even start this. I know pH is -log[H+]
Thanks in advance
Figure the concentration of H+ in each one, convert that concentration(s) to moles in each one, add them, divide by the new volume. Then, figure the pH of that amount.
conc H+ = 10^-pH
So I convert from H+ concentration to moles by just using the molecular weight of a proton?
Also, that will eventually give me molarity mol/L but then how do I go from there to pH?
Not quite. mols in each = M x L = ?
Then after you know (H^+) in mols/L (i.e., molarity) then use the pH formula Bob Pursley gave you in the last line to get pH.
To determine the pH of the final solution, you need to consider the initial pH of the water and the pH of the sodium hypochlorite solution. However, before calculating the pH, it is important to note that mixing two solutions with different pH values will not necessarily result in a final solution with a pH equal to either of the starting pH values.
In this case, you have 25 million gallons of water at a pH of 6.5, and you are adding 17.4 million gallons of sodium hypochlorite solution with a pH of 12.5.
To calculate the pH of the final solution, you need to take into account the dilution caused by adding the sodium hypochlorite solution to the water, as well as the contribution of the sodium hypochlorite to the resulting solution.
First, let's calculate the amount of sodium hypochlorite in the mixture:
Sodium hypochlorite solution concentration = 12.5% by weight
Weight of sodium hypochlorite solution = 17.4 million gallons * 12.5% = 2.175 million gallons
Next, let's consider the dilution factor caused by mixing the two solutions. Adding 17.4 million gallons of sodium hypochlorite solution to 25 million gallons of water results in a total volume of 42.4 million gallons.
To calculate the pH of the final solution, we need to determine the number of moles of H+ and OH- ions present. However, sodium hypochlorite is a strong base, and its contribution to the OH- ion concentration will be negligible compared to the OH- concentration from water (since the sodium hypochlorite solution is highly diluted when mixed with the water).
Therefore, we can approximate the OH- concentration by considering only the OH- concentration contributed by water at the original pH of 6.5.
Now, we can convert this concentration to molarity:
OH- concentration from water = 10^(-pOH) = 10^(-14 + 6.5)
Molarity of OH- from water = OH- concentration / 1000 L
Molarity of OH- from water = (10^(-14 + 6.5)) / 1000
Since the pH is defined as -log[H+], we can calculate the pOH by taking the negative logarithm of the OH- concentration from water.
pOH = -log[(10^(-14 + 6.5)) / 1000]
The pH of the final solution can be calculated as:
pH = 14 - pOH
Calculating these values should give you the pH of the final solution.