Calculate the pH of a solution made by adding 3.20 g of lithium oxide (Li2O) to enough water to make 1.210 L of solution. (Kw = 1.0 10-14)
Li2O + H2O ==> 2LiOH
mols Li2O = 3.20/1.21 = ?
mols Li2O = 2 mols LiOH.
M LiOH = mols LiOH/L LiOH
Then (H^+)(OH^-) = 1E-14
Solve for (H^+), then
pH = -log(H^+)
To calculate the pH of a solution, you need to determine the concentration of H+ ions in the solution. In this case, we will be using the concept of hydrolysis and the fact that lithium oxide (Li2O) is a strong base that completely dissociates in water.
Step 1: Calculate the moles of Li2O:
To do this, we need to convert the mass of Li2O to moles. The molar mass of Li2O is the sum of the atomic masses of lithium (Li) and oxygen (O).
Molar mass of Li2O = (2 x atomic mass of Li) + atomic mass of O
= (2 x 6.94 g/mol) + 16.00 g/mol
= 13.88 g/mol + 16.00 g/mol
= 29.88 g/mol
Now, calculate the moles of Li2O using its molar mass:
moles of Li2O = mass of Li2O / molar mass of Li2O
= 3.20 g / 29.88 g/mol
= 0.107 mol
Step 2: Calculate the concentration of OH- ions:
Since lithium oxide is a strong base, it will react with water to produce hydroxide ions (OH-). The number of moles of OH- ions will be equal to the number of moles of Li2O added to the solution.
moles of OH- = 0.107 mol
Step 3: Calculate the concentration of H+ ions:
According to the concept of hydrolysis, the concentration of H+ ions can be calculated using the ion product of water (Kw) and the concentration of OH- ions.
Kw = [H+][OH-]
Given that Kw = 1.0 x 10^-14 and the concentration of OH- ions is 0.107 mol, we can rearrange the equation to solve for [H+].
[H+] = Kw / [OH-]
= (1.0 x 10^-14) / (0.107 mol)
[H+] = 9.35 x 10^-14 mol/L
Step 4: Calculate the pH:
The pH can be calculated using the formula:
pH = -log[H+]
pH = -log(9.35 x 10^-14 mol/L)
To calculate the pH using a scientific calculator or online calculator, simply input the value of [H+] into the equation and solve for pH.
pH ≈ 13.03
Therefore, the pH of the solution is approximately 13.03.