If 4.56 grams of NaOH and 56.3 grams of Ca(OH)2 are added to enough water to make 1.50 L of solution, what will the pH be?
Start by converting grams to moles. moles = grams/molar mass.
Ca(OH)2 is not all that soluble but since it is make a SOLUTION, I assume it is that soluble.
moles OH from Ca(OH)2 = M x L, then twice that because there two OH ions per mole Ca(OH)2.
mols NaOH = M x L.
Add all the moles together, then
M = total moles/total volume in liters.
Finally, convert OH to pOH, then to pH is the way I would do it.
OK thank you so much! I was wondering whether or not there would be 2 OH ions to account for. Thanks again!
To determine the pH of a solution, we need to calculate the concentration of hydroxide ions (OH-) in the solution.
First, let's calculate the number of moles of NaOH and Ca(OH)2 in the solution.
To find the moles of NaOH:
Given mass of NaOH = 4.56 grams
Molar mass of NaOH = 22.99 g/mol for Na + 16.00 g/mol for O + 1.01 g/mol for H = 39.96 g/mol
Moles of NaOH = mass / molar mass = 4.56 g / 39.96 g/mol = 0.114 moles
To find the moles of Ca(OH)2:
Given mass of Ca(OH)2 = 56.3 grams
Molar mass of Ca(OH)2 = 40.08 g/mol for Ca + 16.00 g/mol for O + 2*(1.01 g/mol for H) = 74.10 g/mol
Moles of Ca(OH)2 = mass / molar mass = 56.3 g / 74.10 g/mol = 0.760 moles
Next, we need to calculate the total volume of the solution:
Given volume of the solution = 1.50 L
Now, let's calculate the concentration of hydroxide ions (OH-) using the moles and volume:
For NaOH:
Concentration of NaOH in moles per liter = moles of NaOH / volume of solution
Concentration of NaOH in moles per liter = 0.114 moles / 1.50 L = 0.0760 M
For Ca(OH)2:
Since Ca(OH)2 dissociates to provide twice as many OH- ions, we need to multiply the moles of Ca(OH)2 by 2.
Concentration of Ca(OH)2 in moles per liter = 2 * moles of Ca(OH)2 / volume of solution
Concentration of Ca(OH)2 in moles per liter = 2 * 0.760 moles / 1.50 L = 1.01 M
Now, to find the total concentration of hydroxide ions:
Total concentration of OH- in moles per liter = concentration of NaOH + concentration of Ca(OH)2
Total concentration of OH- in moles per liter = 0.0760 M + 1.01 M = 1.086 M
Finally, we can find the pOH and then calculate the pH using the relation: pH = 14 - pOH.
To find pOH:
pOH = -log10(OH- concentration)
pOH = -log10(1.086 M) ≈ 0.963
To find pH:
pH = 14 - pOH
pH = 14 - 0.963 ≈ 13.037
Therefore, the pH of the solution will be approximately 13.037.