Calculate the Ph of an aqueous solution that is 3.00% KOH, by mass, and has a density of 1.0242 g/ml.
Assume the mass of the solution is 1024.2 grams, or one liter.
Then three percent (by mass) is KOH. How many moles is that?
Assuming total dissociation, then
[OH}=MolarityKOH= moles/1.0000liter
Then [H]=14-[OH]
and pH= -log[H]
I think bobpursley meant that:
pOH = -log[OH-]
and
pH = 14 - pOH
Use these relationships to get the pH after finding the molarity of KOH = [OH-] as bobpursley suggested.
To calculate the pH of the given solution, we need to find the concentration of hydroxide ions (OH-) first.
Given:
Mass of solution = 100 g (assuming 100 g of solution)
Mass of KOH = 3.00 g (3.00% of 100 g solution)
To find the concentration of KOH in the solution:
Concentration = mass of solute / volume of solution
Volume of solution = mass of solution / density
Volume of solution = 100 g / 1.0242 g/mL = 97.67 mL
Concentration of KOH = 3.00 g / 97.67 mL = 0.0307 g/mL
Now, we can find the molarity (M) of KOH using the molar mass of KOH (39.10 g/mol)
Molarity = concentration / molar mass
Molarity = 0.0307 g/mL / 56.11 g/mol = 0.000548 M
Since KOH is a strong base, we can assume that all KOH completely dissociates in water to release one hydroxide ion (OH-) for every one molecule of KOH. Therefore, the concentration of hydroxide ions (OH-) is also 0.000548 M.
To calculate the pOH, we use the formula pOH = -log[OH-]
pOH = -log(0.000548) = 3.26
Lastly, we can calculate the pH using the equation pH = 14 - pOH
pH = 14 - 3.26 = 10.74
Therefore, the pH of the aqueous solution is approximately 10.74.
To calculate the pH of the aqueous solution of KOH, we need to use the concentration of hydroxide ions (OH-) produced by KOH.
Step 1: Calculate the concentration of KOH in the solution.
The solution is 3.00% KOH by mass, and we know the density of the solution. We can use these values to find the concentration of KOH in grams per liter (g/L).
First, let's assume we have 100 g of the solution. Since the solution is 3.00% KOH by mass, the mass of KOH in the solution is:
Mass of KOH = 3.00% × 100 g = 3.00 g
The volume of the solution can be calculated using its density. We are given that the density is 1.0242 g/mL. To convert it to g/L, we multiply by 1000 (1 L = 1000 mL):
Volume of the solution = 100 g / (1.0242 g/mL) × (1000 mL/L) = 97.69 mL ≈ 97.7 mL
Now, we can find the concentration of KOH in g/L:
Concentration of KOH = Mass of KOH / Volume of the solution
= 3.00 g / (97.7 mL / 1000) = 30.7 g/L
Step 2: Calculate the concentration of hydroxide ions (OH-) produced by KOH.
When KOH dissolves in water, it dissociates into one hydroxide ion (OH-) for every molecule of KOH.
Therefore, the concentration of hydroxide ions is the same as the concentration of KOH in the solution, which is 30.7 g/L.
Step 3: Calculate the pOH of the solution.
The pOH is defined as the negative logarithm (base 10) of the hydroxide ion concentration.
pOH = -log[OH-] = -log(30.7) = 1.512
Step 4: Calculate the pH of the solution.
The pH and pOH of a solution are related by the equation:
pH + pOH = 14
Rearranging the equation, we find:
pH = 14 - pOH = 14 - 1.512 = 12.488
Therefore, the pH of the aqueous KOH solution with a concentration of 3.00% and a density of 1.0242 g/mL is approximately 12.5.