describe briefly how you would prepare a 0.2M solution of KOH in 250cm flask
0.2 M means 0.2 mol/L. You want 0.250 L; therefore, you want 0.2 x (0.250 L/1 L = ? mols.
Weight out ? mols, place in a 250 mL volumetric flask, add some distilled water, swirl until dissolved, then make the mark of the volumetric flask with distilled water, mix thoroughly, stopper. How many grams is ? mol KOH? That's grams = mols x molar mass.
c=n/v Answer n=m/mr
c=0.2 m=0.05.920
v=250mL/1000=0.25L m=46grms
n=?
n=cv
n=0.2.0.25=0.05mol
To prepare a 0.2M solution of KOH (potassium hydroxide) in a 250ml flask, follow these steps:
1. Calculate the required amount of KOH: To make a 0.2M solution, you need to determine how many moles of KOH are required. The formula to calculate moles is: moles = molarity x volume (in liters). In this case, you want 0.2 moles of KOH in 1 liter of solution. Therefore, to prepare 250ml (0.25 liters), you need 0.2 x 0.25 = 0.05 moles of KOH.
2. Determine the molecular weight of KOH: The molecular weight of KOH is calculated by adding the atomic weights of potassium (K), oxygen (O), and hydrogen (H). The atomic weights are: K = 39.1 g/mol, O = 16.0 g/mol, and H = 1.0 g/mol. Therefore, the molecular weight of KOH is 39.1 + 16.0 + 1.0 = 56.1 g/mol.
3. Calculate the mass of KOH required: The mass of KOH required can be calculated using the formula: mass = moles x molecular weight. In this case, the mass of KOH required is 0.05 x 56.1 = 2.805 grams.
4. Weigh the required amount of KOH: Use an analytical balance to weigh out 2.805 grams of KOH. It is important to handle the KOH with care as it is a strong base and can cause burns. Use appropriate protective equipment such as gloves and goggles.
5. Dissolve KOH in water: Add the weighed KOH to a beaker or flask with approximately half of the required volume (125ml) of distilled water. Gently swirl the solution to help dissolve the KOH. Be cautious as the dissolving process is exothermic and can generate heat.
6. Bring the volume to the desired level: Once the KOH is completely dissolved, transfer the solution to a 250ml volumetric flask using a funnel if necessary. Rinse the beaker or flask with distilled water to ensure all KOH is transferred. Finally, add distilled water to the flask until the total volume reaches the 250ml mark on the neck of the flask. Stop when the bottom of the meniscus is on the mark.
7. Mix well: Invert the flask several times to ensure thorough mixing of the KOH solution.
Congratulations! You have successfully prepared a 0.2M solution of KOH in a 250ml flask. Be sure to label the flask with the contents and concentration for future reference.
To prepare a 0.2M solution of KOH (potassium hydroxide) in a 250 mL flask, you will need:
1. Calculate the amount of KOH needed:
- Determine the molar mass of KOH, which consists of potassium (K), oxygen (O), and hydrogen (H). The molar mass of potassium is 39.1 g/mol, oxygen is 16.0 g/mol, and hydrogen is 1.0 g/mol. Thus, the molar mass of KOH is 39.1 + 16.0 + 1.0 = 56.1 g/mol.
- Next, calculate the number of moles (n) required using the formula:
n = Molarity × Volume (in L)
Since you want a 0.2M solution in a 250 mL flask (0.250 L), the number of moles needed can be calculated as:
n = 0.2 M × 0.250 L = 0.050 mol.
- Finally, calculate the mass of KOH required using the formula:
Mass = Number of moles × Molar mass
Mass = 0.050 mol × 56.1 g/mol = 2.81 g.
2. Measure and add the calculated mass of KOH to a clean and dry 250 mL flask. Be cautious while handling KOH, as it is a corrosive chemical. Use protective equipment, such as gloves and safety goggles.
3. Add distilled water to the flask and dissolve the KOH completely. Start with a small amount of water and swirl the flask gently until the solution is homogeneous.
4. Once the KOH has dissolved completely, add more distilled water to bring the total volume up to the 250 mL mark on the flask. Again, take care to swirl gently to avoid splashing or foaming.
5. Finally, seal the flask tightly with a stopper or a lid to prevent evaporation.
Please note that KOH is a strong base, and it is essential to handle it safely, follow proper lab protocols, and dispose of any waste according to environmental regulations.