calculate the Ph of a solution composed of 0.75 grams of KOH dissolved in 500ml of water. assume total ionization.
KOH ==> K^+ + OH^-
mols KOH = grams/molar mass = ?
M KOH = mols KOH/L solution = ?
pOH = -log(KOH)
Then pH + pOH = pKw = 14. You know pKw and pOH, calculate pH.
To calculate the pH of a solution, we need to determine the concentration of the hydroxide ions (OH-) in the solution. We can do this by first finding the number of moles of KOH and then dividing it by the total volume of the solution.
1. Start by finding the number of moles of KOH:
- Determine the molar mass of KOH by adding up the atomic masses of potassium (K), oxygen (O), and hydrogen (H). The atomic masses are: K = 39.10 g/mol, O = 16.00 g/mol, H = 1.01 g/mol.
- Calculate the molar mass of KOH: 39.10 g/mol + 16.00 g/mol + 1.01 g/mol = 56.11 g/mol.
- Convert the mass of KOH to moles by dividing the mass by the molar mass: 0.75 g / 56.11 g/mol = 0.0134 mol.
2. Calculate the concentration of hydroxide ions (OH-):
- Divide the number of moles of KOH by the total volume of the solution. The total volume is given as 500 mL, but we need to convert it to liters: 500 mL = 0.500 L.
- Calculate the concentration in moles per liter (Molarity): 0.0134 mol / 0.500 L = 0.0268 M.
3. Calculate the pOH of the solution:
- The pOH is the negative logarithm (base 10) of the hydroxide ion concentration (OH-). pOH = -log[OH-].
- In this case, the concentration is 0.0268 M: pOH = -log(0.0268) = 1.57.
4. Calculate the pH of the solution:
- The pH can be determined using the relation: pH + pOH = 14.
- Therefore, pH = 14 - pOH = 14 - 1.57 = 12.43.
Hence, the pH of the solution composed of 0.75 grams of KOH dissolved in 500 mL of water (assuming total ionization) is approximately 12.43.