Calculate [OH-] in a solution containing 100g of potassium hydroxide in 2.50L solution. Potassium hydroxide is a strong base.
Understand the Problem
The question is asking us to calculate the hydroxide ion concentration [OH-] in a solution made by dissolving a specified mass of potassium hydroxide (KOH) in a given volume of solution. We will do this by determining the number of moles of KOH in 100g and then calculating the concentration of OH- ions produced in the solution.
Answer
$[OH^-] = \frac{100 \text{ g} / 56.1 \text{ g/mol}}{\text{Volume in liters}}$
Answer for screen readers
The concentration of hydroxide ions $[OH^-]$ will depend on the volume of the solution. For example, if the solution volume is 1 L, the concentration would be calculated as: $$ [OH^-] = \frac{\text{Moles of KOH}}{1 \text{ L}} $$.
Steps to Solve
- Calculate moles of KOH
First, we need to find the number of moles of potassium hydroxide (KOH) using its molar mass.
The molar mass of KOH can be calculated as follows:
- Potassium (K) = 39.1 g/mol
- Oxygen (O) = 16.0 g/mol
- Hydrogen (H) = 1.0 g/mol
Adding these together gives: $$ \text{Molar Mass of KOH} = 39.1 + 16.0 + 1.0 = 56.1 \text{ g/mol} $$
Next, we can calculate the number of moles of KOH in 100 g: $$ \text{Moles of KOH} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{100 \text{ g}}{56.1 \text{ g/mol}} $$
- Calculate number of OH- ions produced
Since each KOH molecule produces one hydroxide ion (OH-), the number of moles of OH- will be equal to the moles of KOH calculated previously.
- Calculate concentration of OH- ions
We need to convert moles of OH- into concentration. If the solution volume is given in liters (for example, assume we have 1 L of solution), we can find the concentration: $$ [OH^-] = \frac{\text{Moles of OH-}}{\text{Volume in liters}} $$
If the volume is not given, you would need to specify that to calculate the concentration.
The concentration of hydroxide ions $[OH^-]$ will depend on the volume of the solution. For example, if the solution volume is 1 L, the concentration would be calculated as: $$ [OH^-] = \frac{\text{Moles of KOH}}{1 \text{ L}} $$.
More Information
The concentration of hydroxide ions (OH-) in a solution affects its pH significantly. Higher concentrations of hydroxide ions result in more basic solutions. Potassium hydroxide is a strong base, meaning it fully dissociates in water to release OH- ions.
Tips
- Forgetting to convert grams to moles by not using the molar mass.
- Not adjusting the volume of the solution to liters when calculating concentration.
AI-generated content may contain errors. Please verify critical information
