I have test procedure to evaluate the clarity of a sodium hydroxide (NaOH) sample that goes like this:
Dissolve 10g of NaOH in carbon dioxide free water and dilute to 100ml with the same solvent.
Please explain how to perform this test.
Do I boil 100ml of deionized water and pour the hot water into a beaker containing 10g of NaOH?
Thanks.
Definitely not, for two reasons.
1. the total volume after solution may exceed 100ml, in which case the required concentration is not attained.
2. DO NOT pour hot water onto solid NaOH, it is an extremely exothermic process and you can end up splashing very corrosive NaOH onto your face or even your eyes. Always put solid NaOH into cold water, giving enough time for the heat to dissipage.
Thanks, can you then explain the exact steps (including the apparatus to use) so that the procedure can be followed?
Thanks a lot:)
I assume you have some CO2 free water. Place 10 g solid NaOH in a 100 mL volumetric flask and add some CO2 free water (about 25 mL or so). When the solid has dissolved (it is quite exothermic as Mathmate has written), let it cool to room temperature, then dilute to the 100 mL mark with CO2 free water.
Note: I would note that if you are trying to prepare a NaOH solution that is free of carbonate ion, this isn't the way to do it. Why? Because solid NaOH picks up CO2 from the air and forms Na2CO3.
Thanks Dr Bob,the purpose of this experiment is to test for the clarity of my sodium hydroxide sample.
I intend to boil deionized water to get CO2 free water, cool the water and add it to a 100mL volumetric flask containing 10g of solid NaOH. Would that be alright?
Also, can you share with me how to prepare a NaOH solution that is free from carbonate ion?
Thanks a lot.
OK. Boil the water, add about 25 mL of the cooled water to the 100 mL volumetric flask containing the solid NaOH, let the NaOH dissolve, then let the whole thing cool. Finally, dilute to the 100 mL mark.
How to prepare carbonate free NaOH. Prepare a concd solution of NaOH by dissolving solid NaOH in deionized water (you want about 50% NaOH solution but I like to make it stronger than that). Na2CO3 is not very soluble in such a concd NaOH solution. Allow to stand (I usually suggest several days), then pipet a portion of the clear, colorless solution into a clean flask and dilute with water. This solution must then be standardized by an appropriate titration. Here is a site you can read about it. (Broken Link Removed)
To perform the test procedure, you need to follow the steps described:
1. Start by weighing out exactly 10 grams of sodium hydroxide (NaOH) using a balance. Ensure that the balance is calibrated properly and free from any contamination.
2. Use carbon dioxide (CO2) free water to dissolve the NaOH. Deionized water is typically used for this purpose, but you can also use distilled water if it is carbon dioxide free.
3. Gradually add the 10 grams of NaOH into a clean and dry beaker. It's important to choose a beaker that is appropriate in size to hold both the water and NaOH.
4. Now, measure out 100 milliliters (ml) of the carbon dioxide free water using a measuring cylinder or pipette. It's important to be precise with the volume measurement.
5. Slowly add the 100 ml of water to the beaker containing the NaOH. It's usually recommended to add the water in small increments while stirring continuously to ensure proper dissolution.
6. Continue stirring until all the NaOH is completely dissolved in the water. You may notice that the solution gets hot due to the exothermic nature of the reaction between NaOH and water. It is not necessary to boil the water beforehand, but ensure that the water is at room temperature or slightly above.
7. Once the NaOH is fully dissolved, you can transfer the solution to a clean and dry 100 ml volumetric flask if you want to ensure accurate volume measurement. However, if accuracy is not critical for your test, you can use the beaker directly.
It's important to note that when working with NaOH, always handle it with caution and use appropriate safety measures, such as wearing gloves and eye protection. Also, ensure that you are working in a well-ventilated area to avoid inhaling any fumes.
By following these steps, you will be able to prepare a 100 ml solution of sodium hydroxide (NaOH) with carbon dioxide free water for clarity evaluation.