Calculate the pH of 0,3g calcium hydroxide dissolved in water to give 500ml solution.
To calculate the pH of a solution of calcium hydroxide, we first need to determine the concentration of hydroxide ions in the solution.
Step 1: Convert the mass of calcium hydroxide to moles.
The molar mass of calcium hydroxide (Ca(OH)2) is calculated by summing the atomic masses of its constituents:
- Calcium (Ca) has a molar mass of 40.08 g/mol
- Oxygen (O) has a molar mass of 16.00 g/mol
- Hydrogen (H) has a molar mass of 1.01 g/mol
Since there are two hydroxide (OH-) ions in calcium hydroxide, we multiply the molar mass by 2.
Molar mass of Ca(OH)2 = (40.08 g/mol + 16.00 g/mol + 1.01 g/mol) * 2 moles = 74.16 g/mol
Next, we convert the mass of calcium hydroxide to moles using the equation:
moles = mass / molar mass
moles = 0.3 g / 74.16 g/mol = 0.00405 mol
Step 2: Calculate the concentration of hydroxide ions.
Since calcium hydroxide dissociates completely in water, each mole of calcium hydroxide produces two moles of hydroxide ions (OH-).
Concentration of OH- ions = (moles of hydroxide ions) / (volume of solution in liters)
Given that the volume of the solution is 500 mL, which is equivalent to 0.5 L:
Concentration of OH- ions = 0.00405 mol / 0.5 L = 0.0081 mol/L
Step 3: Calculate the pOH of the solution.
The pOH is the negative logarithm (base 10) of the hydroxide ion concentration:
pOH = -log10(OH- concentration)
pOH = -log10(0.0081) ≈ 2.09
Step 4: Calculate the pH of the solution.
The pH of a solution can be determined using the equation:
pH = 14 - pOH
pH = 14 - 2.09 ≈ 11.91
Therefore, the pH of a solution containing 0.3 g of calcium hydroxide dissolved in 500 mL of water is approximately 11.91.
mols Ca(OH)2 = grams/molar mass.
mols OH^- = 2x that
M OH^- = mols OH^-/L solution
pOH = -log(OH^-)
pH + pOH = pKw = 14.
After you have pOH you have pKw, solve for pH.