Describe how you could make 5 mL of 2M potassium hydroxide solution if you have potassium hydroxide pellets available.
You want how many moles KOH? That is M x L = ? moles KOH.
moles KOH = grams KOH/molar mass KOH. YOu know molar mass and moles, solve for grams. A quick note to say that KOH is hygroscopic and it picks up water as well as CO2 from the air; therefore, one can't use KOH as a primary standard because as soon as the new bottle is opened it becomes contaminated with H2O and CO2. The CO2 forms KHCO3 and K2CO3.
To make a 5 mL of 2M potassium hydroxide (KOH) solution using potassium hydroxide pellets, you will need to follow these steps:
1. Determine the molar mass of potassium hydroxide (KOH). The molar mass of KOH is found by adding the atomic masses of potassium (K), oxygen (O), and hydrogen (H) together. The atomic masses of K, O, and H are approximately 39.10 g/mol, 16.00 g/mol, and 1.01 g/mol, respectively. So, the molar mass of KOH is 39.10 g/mol + 16.00 g/mol + 1.01 g/mol = 56.11 g/mol.
2. Calculate the amount of potassium hydroxide pellets needed to make a 2M solution. The formula to calculate the mass of solute required is: mass (g) = volume (L) × molarity (mol/L) × molar mass (g/mol). Given that the desired volume is 5 mL (which is converted to 0.005 L) and the desired molarity is 2M, we have: mass (g) = 0.005 L × 2 mol/L × 56.11 g/mol = 0.5611 g.
3. Weigh the required amount of potassium hydroxide pellets (0.5611 g) using a digital balance. Make sure to use proper safety precautions and work in a well-ventilated area, as potassium hydroxide is a strong base.
4. Dissolve the weighed potassium hydroxide pellets in a small volume of deionized or distilled water while stirring gently. It is crucial to add the water carefully, as the reaction produces heat and can cause splattering. It is recommended to use a heat-resistant container to minimize any potential hazards. The volume of water needed may depend on the size of the container but should be just enough to dissolve the pellets.
5. After the pellets are completely dissolved, transfer the solution to a 5 mL measuring cylinder or any other small container. It is essential to ensure accuracy in measuring the final volume.
6. Rinse the container used for making the solution with deionized or distilled water to transfer any remaining solution to the measuring cylinder or container. This step helps to ensure that the desired volume of 5 mL is maintained.
Following these steps will enable you to make a 5 mL of 2M potassium hydroxide solution using potassium hydroxide pellets. Remember to handle potassium hydroxide with care and dispose of it properly after usage.