If 80g of NaOH is added to 100mL water, what is the pH of the resulting solution?

moles NaOH = grams/molar mass

M NaOH = moles NaOH/L solution.
(OH^-) = (NaOH)
pOH = -log(OH^-), then convert to pH by
pH + pOH = pKw = 14'=

Technically, this is not the correct answer. Technically, the correct answer cannot be obtained UNLESS one knows the density of the solution. The reason is that the definition of M is moles/L of solution and the problem doesn't say that; i.e., it asks, "If 80 g NaOH is ADDED TO 100 mL water....." That will produce MORE than 100 mL of solution and without the density the volume of the solution is unknown. However, I think the spirit of the problem is to assume the density of the solution is 1.0 g/mL which means the solution is 100 mL.

To determine the pH of a solution, we need to know the concentration of hydrogen ions (H+). Sodium hydroxide (NaOH) is a strong base and dissociates in water to produce hydroxide ions (OH-). So, in this case, we can determine the concentration of hydroxide ions first and then use the relationship between hydroxide and hydrogen ion concentrations to find the pH.

First, let's calculate the concentration of hydroxide ions (OH-) in the solution. We have 80g of NaOH added to 100mL of water. To determine the concentration, we need to convert the mass to moles using the molar mass of NaOH.

The molar mass of NaOH is:
Na (22.99 g/mol) + O (16.00 g/mol) + H (1.01 g/mol) = 39.99 g/mol.

Since we have 80g of NaOH, the number of moles can be calculated as:
80g / 39.99 g/mol = 2.00 mol.

Now, we need to calculate the concentration of hydroxide ions. Since we have 100mL of water, which is equivalent to 0.100L, and 2.00 moles of NaOH, we can use the formula:

Concentration (in mol/L) = moles / volume (in L).
Concentration of OH- ions = 2.00 mol / 0.100 L = 20 mol/L.

Next, we can use the relationship between the concentration of hydroxide (OH-) and hydrogen (H+) ions in water. In neutral water, the concentration of H+ and OH- ions is equal, and is equal to 1.0 x 10^-7 mol/L.

Taking the negative logarithm (base 10) of the concentration of hydrogen ions (H+), we can find the pH.

pH = -log[H+].

Since OH- and H+ ions are related by the equation:
[H+] x [OH-] = 1.0 x 10^-14 mol^2/L^2,

we can find the concentration of hydrogen ions:

[H+] = 1.0 x 10^-14 / [OH-] = 1.0 x 10^-14 / 20 = 5.0 x 10^-16 mol/L.

Now, let's calculate the pH:

pH = -log(5.0 x 10^-16) ≈ 15.30.

So, the pH of the resulting solution is approximately 15.30.