What mass in grams of potassium hydroxide is cntained in 500 mL of solution that has a pH of 11.5?
pH = 11.5
pOH = 14 - 11.5 = 2.5
pOH = -log(OH^-) ] 2.5
(OH^-) = ??
KOH ==> K^+ + OH^-
This is a strong base.
You have the (OH^-) which is mols/L. Take 1/2 that to find the mols in 500 mL, Then grams = mols x molar mass. Post your work if you get stuck.
To determine the mass of potassium hydroxide (KOH) in the solution, we need to consider the concentration of hydroxide ions (OH-) present. The pH value can be used to calculate the concentration of hydroxide ions in the solution.
The pH scale is a logarithmic scale that measures the acidity or basicity of a solution. A pH of 7 is neutral, values below 7 are acidic, and values above 7 are basic. Since the given pH is 11.5, it indicates that the solution is basic.
The pH can be related to the concentration of hydroxide ions using the equation:
pOH = 14 - pH
In this case, since the pH is 11.5, we can calculate the pOH:
pOH = 14 - 11.5
pOH = 2.5
Now, we can convert the pOH value to the hydroxide ion concentration (in moles per liter) using the equation:
pOH = -log[OH-]
Taking the antilog (inverse log) of both sides, we have:
[OH-] = 10^(-pOH)
[OH-] = 10^(-2.5)
[OH-] = 0.00316 M
Next, we need to calculate the number of moles of potassium hydroxide (KOH) using the concentration and the volume of the solution.
Since the volume is given in mL, we need to convert it to liters for the calculation, by dividing it by 1000:
Volume = 500 mL ÷ 1000
Volume = 0.5 L
The number of moles can be calculated using the formula:
moles = concentration (in M) × volume (in L)
moles = 0.00316 M × 0.5 L
moles = 0.00158 mol
Finally, we can calculate the mass of KOH using the molar mass of KOH, which is 56.11 g/mol:
mass = moles × molar mass
mass = 0.00158 mol × 56.11 g/mol
mass ≈ 0.089 g
Therefore, approximately 0.089 grams of potassium hydroxide (KOH) is contained in 500 mL of solution with a pH of 11.5.