Starting with 50cm³ of 2.8M sodium hydroxide, describe how a sample of pure sodium sulphate crystals can be prepared
I don't know
millimoles NaOH initially = mL x M = 50 mL x 2.8 M = 140
2NaOH + H2SO4 ==> Na2SO4 + 2H2O
Start with 50 cc of 2.8 M NaOH, add140/2 = 70 millimoles H2SO4, allow the solution to cool, heat to remove the water and dry the Na2SO4 crystals in an oven @ 105 C. Done.
To prepare a sample of pure sodium sulfate crystals starting with 50cm³ of 2.8M sodium hydroxide, you will need the following materials:
- Sodium hydroxide solution (2.8M)
- Sulfuric acid (concentrated)
- Beaker or flask
- Stirring rod
- Filter paper
- Funnel
- Bunsen burner or heating plate
- Evaporating dish
- Glass rod
- Ice bath or refrigerator
Here is a step-by-step procedure to prepare pure sodium sulfate crystals:
1. Measure 50cm³ of the 2.8M sodium hydroxide solution using a graduated cylinder and transfer it into a beaker or flask.
2. Slowly add concentrated sulfuric acid dropwise to the sodium hydroxide solution while stirring continuously. The reaction between sodium hydroxide and sulfuric acid will produce sodium sulfate and water:
2NaOH + H2SO4 → Na2SO4 + 2H2O
Continue adding sulfuric acid until the pH reaches neutral (pH 7). You can use pH paper or a pH meter to monitor the pH level.
3. Once the pH is neutral, filter the mixture using filter paper and a funnel to separate the liquid from any remaining solid impurities.
4. Transfer the filtered solution into an evaporating dish. Heat the solution on a Bunsen burner or heating plate to evaporate the liquid. Make sure to use a fume hood or work in a well-ventilated area as the evaporation process may produce fumes.
5. As the liquid evaporates, sodium sulfate crystals will start to form. Gently stir the solution using a glass rod to encourage crystal growth and prevent the crystals from sticking to the dish.
6. Once most of the liquid has evaporated and crystal formation is observed, remove the evaporating dish from the heat source. Allow the dish to cool to room temperature.
7. To obtain larger and more pure crystals, you can further cool the dish by placing it in an ice bath or refrigerating it for a few hours. This slower cooling process will encourage crystal formation and improve crystal purity.
8. Once the dish and crystals have reached room temperature or cooled further in the ice bath or refrigerator, carefully remove the sodium sulfate crystals from the dish using a spatula or similar tool. Place the crystals on a clean, dry surface to air dry.
9. After the crystals have dried completely, you will have a sample of pure sodium sulfate crystals.
Important Note: Please exercise caution and follow proper lab safety protocols while conducting chemical experiments. It is advisable to perform this procedure in a controlled laboratory setting or under the guidance of a professional chemist.
To prepare a sample of pure sodium sulfate crystals from 2.8M sodium hydroxide, we will need to perform a reaction that converts the sodium hydroxide into sodium sulfate. Here are the steps to do this:
Step 1: Calculate the required amount of sodium hydroxide.
The molar concentration of sodium hydroxide (2.8M) tells us that there are 2.8 moles of sodium hydroxide in 1 liter (1000 cm³) of solution. We want to start with 50 cm³ of this solution, so we need to calculate the number of moles in this volume.
Using the formula:
moles = concentration (M) x volume (L),
moles of sodium hydroxide in 50 cm³ = 2.8M x (50 cm³ / 1000 cm³) = 0.14 moles.
Step 2: Determine the stoichiometry of the reaction.
The balanced chemical equation for the reaction between sodium hydroxide and sulfuric acid, which produces sodium sulfate, is:
2NaOH + H2SO4 -> Na2SO4 + 2H2O.
From this equation, we can see that 2 moles of sodium hydroxide react with 1 mole of sulfuric acid (H2SO4) to produce 1 mole of sodium sulfate (Na2SO4).
Step 3: Calculate the amount of sulfuric acid needed.
Since the stoichiometry of the reaction is 2:1, we will need half as many moles of sulfuric acid as sodium hydroxide. Therefore, we need 0.07 moles of sulfuric acid.
Step 4: Prepare the sulfuric acid solution.
Assuming we have a concentrated sulfuric acid solution, we need to dilute it to the appropriate concentration to react with the sodium hydroxide solution. Let's say we want to prepare a 1M solution of sulfuric acid. We can use the formula:
concentration (C1) x volume (V1) = concentration (C2) x volume (V2),
where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume.
Assuming we have concentrated sulfuric acid with a concentration, for example, 10M, and we want to prepare a 1M solution, we can rearrange the formula as follows:
V1 = (C2 x V2) / C1,
V1 = (1M x (0.07 moles / 10M)) = 0.007 L (or 7 cm³).
So, we need to measure 7 cm³ of the concentrated sulfuric acid and dilute it with water to a final volume of 50 cm³. This will give us a 1M solution of sulfuric acid.
Step 5: Mixing and Reaction.
In a suitable container, add the 50 cm³ of 2.8M sodium hydroxide solution, slowly add the 7 cm³ of 1M sulfuric acid solution while stirring continuously. This will initiate the reaction between the sodium hydroxide and sulfuric acid, forming sodium sulfate.
Step 6: Crystallization and Isolation.
Allow the mixture to cool down to room temperature or below and set it aside for a period of time to let the sodium sulfate crystals form. The solution will become supersaturated with sodium sulfate, causing the crystals to precipitate out. The crystals can then be isolated by filtration or other suitable methods and washed with distilled water to remove any impurities.
Finally, the obtained sodium sulfate crystals can be collected and dried to obtain a sample of pure sodium sulfate crystals.