[MathisFun]

--Provide the calculations and experimental procedure necessary to make the following solution: 10.00 mL of a 0.0300 M solution of CH₃COOH from a stock solution with a concentration of 0.0780 M.

Use the equation: M₁V₁ = M₂V₂.
V1 = (10.00 mL)(0.0300 mol/L) = 0.300 mol
V1 = (0.300 mol/0.0780 mol/L) = 3.85 mL

--Explain to a person new to lab how to make this solution. Specifically state "which glassware" you would use and include the appropriate precision of said glassware in your calculations.

Here is the list of available glassware that can be used:
-Beakers, mL:
600
400
250
150
100
50
30
20
-Burets, mL:
50
25
-Graduated Cylinders, mL:
100
50
10
-Volumetric Flasks, mL:
100
50
25
10
-Volumetric Pipets, mL:
25
20
10
8
7
5
3
2
1

Obtain a 10.00 mL volumetric flask and rinse with distilled water. Add about 5.00-7.00 mL of distilled water to the volumetric flask. Obtain the stock solution from the carboy with the appropriate marking for CH₃COOH. Add more than the desired amount of stock solution to a 10.00 mL graduated cylinder, in this case, 5.00 mL more, to prevent loss of substance due to mishandling. Use a 10.00 mL graduated cylinder to dole out the 3.85 mL of CH₃COOH to the 10.00 mL volumetric flask. Stopper the flask and invert several times to mix the contents well. Add more distilled water, until the meniscus is level with the calibration mark. Stopper the flask and invert 20 times.

Given my list of available glassware above, is there a more precise way of transferring the needed 3.85 mL of CH₃COOH to the 10.00 volumetric flask?

I have heard of the Class A, 5 ml volumetric serological pipe and Class A adjustable pipettor (1000 - 5000 ul), which is adjustable to 10ul, but it can't be included, since it's not on the list.

I'm also aware that when the equipment required to measure a small quantity is not readily available, an individual measures out multiple quantities, dilutes it, and takes an aliquot for the needed quantity. But, an aliquot if off-limits as well.

My conclusion is to use the 10.00 mL graduated cylinder. The 5.00 mL pipet available only contains the 'TC' and 'TD' markings, so no microliters. My other option is to go with the 25.00 mL buret.

Would like some feedback on this, thanks.

[Arkcon]

For preparing stock solutions, and a dilution series of the stock to get the dilution you want, you always use volumetric glassware.  Solution transfers are always done with a volumetric pipette.  I get lazy, and use an electronic pipette sometimes, but that's just technically a no-no.  Not absolutely, because it should be accurate and precise enough, but still, you said, when you set up the experiment, that you were working volumetrically (or implied it at least,) that means volumetric glassware.  Your 5ml volumetric pipette should have gradations, even if its not a serolgical pipette.  But if it doesn't you'll have to get the dilution some other way.

Buretts are used to dispense reagents volumetrically, they aren't used to prepare solutions.  You dispense into an Erlenmeyer flask, because only that type of flask sits flat, and swirls titrating reagent properly, giving you a clear view.

Beakers and graduated cylinders aren't accurate enough for analytical work.  They're used for synthetic reactions, as an example.

[MathisFun]

Thanks for the input. That electronic pipette sounds like some heavy machinery, would like to get my hands on it someday.

In using the buret, other than being less precise with the measurement, how would it affect the final result of the mixture?

[Arkcon]

You kinda just don't use a buret that way.  Actually, sometimes, in a beginner class, an expensive reagent is put into a large buret, and each student uses it as a dispenser for the reagent.  There are also auto dispensers attached to bottles that dispense a fixed amount, they are also called burettes.  But still, you don't use a buret to measure a liquid.  You use it to dispense to the endpoint, then you read what you dispensed to calculate the titer.  I'm guessing, you're expected to learn this distinction, so it would be technically incorrect to use a buret as a dispenser.  Think about it, if you overfill a pipette, you can correct it, but if you overdispense from a buret, you can't put any back.

[MathisFun]

Thanks Arkcon for the distinction between measuring with a buret and pipet. As you can tell, I'm new at this sort of thing.

[MathisFun]

Arkcon, thanks again for the suggestions. As it turned out, the instructor accepted using a graudated cylinder (10.00 mL) and a buret (25.00 mL) to measure out the pesky 3.85 mL. Albeit, it isn't precise, many in the class used this approach, which worked out fine.