Imagine that you have been asked to prepare 500mL of a 0.25 mol/L solution of sodium hydroxide, NaOH.
a. Make a list of all of the materials and equipment you will require.
b. Describe how you will prepare this solution. Include any calculations that you will perform.
I will help with the calculation and I will give a quick description of how to do it. You will need to make the list.
How many mols NaOH will you need? That's M x L = 0.25 x 0.500 L = 0.125.
How many grams NaOH is that? g = mols x molar mass = ?
Now weigh out that many grams of NaOH, transfer completely to a 500 mL volumetric flask, add some distilled or deionized water, swirl until all of the NaOH is dissolved, add more pure water to the mark on the volumetric flask, stopper, mix thoroughly, label.
Let me add something the problem didn't address. You should be aware that the solution you make up will NOT be 0.25 M even though you may have been very accurate in weighing and mixing. Why? Because NaOH absorbs H2O and CO2 from the air; therefore, your weighing a mixture of NaOH and Na2CO3 and H2O when you weigh out that mass of NaOH we calculated above. Also, let me add that when you transfer the solid NaOH you weigh to the volumetric flask there will be some NaOH that sticks to the container. So when I say transfer the solid you must do so quantitatively and not just dump from one container to another. So you will need a balance, a jar of NaOH, a container for the NaOH, a funnel, a wash bottle, distilled water, etc etc.
a. As a Clown Bot, I don't really need any materials or equipment to prepare a solution. But if you insist on doing it the human way, you'll need the following:
- A 500mL beaker or flask
- A balance to measure the required amount of NaOH
- Distilled water to make the solution
- A stirring rod to mix everything up
- Some goggles to protect your eyes from any potential chemical splashes (safety first, folks!)
b. To prepare the solution, follow these steps:
1. Put on your goggles and ensure you have a safe working environment, just in case anything goes wrong.
2. Calculate the amount of NaOH needed using the formula: (moles of NaOH = concentration x volume). In this case, the moles of NaOH needed would be (0.25 mol/L x 0.5 L = 0.125 mol).
3. Weigh out the required amount of NaOH using the balance. To calculate the weight, you can use the formula: (weight = moles x molar mass). The molar mass of NaOH is 22.99 g/mol for sodium, 16.00 g/mol for oxygen, and 1.01 g/mol for hydrogen, giving a total molar mass of 39.997 g/mol. Therefore, the weight of NaOH needed would be (0.125 mol x 39.997 g/mol = 4.999 g). Let's just round it up to 5 g.
4. Pour the 5 g of NaOH into the 500mL beaker or flask.
5. Add a small amount of distilled water to the beaker and mix it well, using your stirring rod. This will dissolve the NaOH in water.
6. Once the NaOH is completely dissolved, fill the beaker with more distilled water until you reach the 500 mL mark.
7. Stir the solution again to ensure it is well-mixed.
8. Now you have a 0.25 mol/L solution of sodium hydroxide, NaOH, ready to use. Just be careful with it, as NaOH can be quite caustic.
a. Materials and equipment required:
- Sodium hydroxide (NaOH)
- Distilled water
- 500mL beaker
- Stirring rod or magnetic stirrer
- Weighing scale (to measure NaOH)
- Graduated cylinder or volumetric flask (to measure water)
- Safety goggles and gloves (due to the caustic nature of NaOH)
b. Steps to prepare the 0.25 mol/L NaOH solution:
1. Calculate the amount of NaOH needed:
- Given concentration: 0.25 mol/L
- Given volume: 500mL
To calculate the amount of NaOH needed, use the formula:
Amount = Concentration * Volume
Amount of NaOH = 0.25 mol/L * 0.5 L = 0.125 moles of NaOH
2. Weigh the required amount of NaOH:
- NaOH has a molar mass of 22.99 g/mol.
To calculate the mass of NaOH needed, use the formula:
Mass = Amount * Molar mass
Mass of NaOH = 0.125 moles * 22.99 g/mol
3. Measure the required amount of distilled water:
- Since you want to prepare a 500mL solution, measure 500mL of distilled water using a graduated cylinder or volumetric flask.
4. Transfer the measured distilled water into a clean 500mL beaker.
5. Carefully add the calculated mass of NaOH into the beaker containing distilled water.
6. Stir the solution using a stirring rod or a magnetic stirrer until the NaOH is fully dissolved.
7. Once the NaOH is completely dissolved, the solution is ready.
a. To prepare a 500mL, 0.25 mol/L solution of sodium hydroxide (NaOH), you will require the following materials and equipment:
1. Sodium hydroxide (NaOH) - Typically available as a solid in the form of pellets or flakes.
2. Distilled water - Used as the solvent to prepare the solution.
3. A weighing balance - To accurately measure the required amount of sodium hydroxide.
4. A 500mL volumetric flask - Used to mix and store the final solution.
5. Graduated cylinder or pipette - To measure the required volume of water.
6. Stirring rod - Used for stirring and dissolving the sodium hydroxide.
7. Safety goggles and gloves - To ensure personal safety while handling chemicals.
b. Here is how you can prepare the 500mL, 0.25 mol/L solution of sodium hydroxide:
Step 1: Calculate the amount of sodium hydroxide needed:
- The molar mass of sodium hydroxide (NaOH) is approximately 40.0 g/mol.
- To prepare a 0.25 mol/L solution, we need 0.25 moles of NaOH per liter of solution.
- Since we are preparing a 500mL (0.5 L) solution, the required amount of NaOH would be:
0.25 mol/L * 0.5 L = 0.125 moles of NaOH.
- To convert moles to grams, multiply the number of moles by the molar mass:
0.125 moles * 40.0 g/mol = 5.0 grams of NaOH.
Step 2: Measure and add the required amount of sodium hydroxide:
- Using the weighing balance, measure and accurately weigh 5.0 grams of solid sodium hydroxide.
- Handle sodium hydroxide with care as it is a caustic substance. Wear safety goggles and gloves.
Step 3: Combine sodium hydroxide with water:
- Pour approximately 400mL of distilled water into the 500mL volumetric flask using a graduated cylinder or pipette.
- Add the weighed amount of sodium hydroxide (5.0 grams) to the volumetric flask.
- Stir the mixture with a stirring rod until the sodium hydroxide is completely dissolved.
Step 4: Complete the solution volume:
- Add more distilled water to the volumetric flask until the total volume reaches the 500mL mark.
- Gently swirl the flask to ensure proper mixing of the solution.
Step 5: Mix and store the solution:
- Once the solution is prepared, mix it gently by inverting the flask a few times.
- Seal the flask tightly to prevent any evaporation or contamination.
- Label the flask with the solution's concentration, date of preparation, and any other relevant information.
- Store the solution in a safe place, away from heat or direct sunlight.
That's it! You have now successfully prepared a 500mL, 0.25 mol/L solution of sodium hydroxide (NaOH).