1998 Mar;54(1):19-32. The effect of serial dilution error on calibration inference in immunoassay. Higgins KM(1), Davidian M, Chew G, Burge H.

It depends on what degree of accuracy you need and what order of magnitude the final concentrations will be. If you need high accuracy and concentrations are in the range you are describing, I would put a class A volumetric flask on a balance, add the appropriate weight of solute, add water to not quite the full volume, dissolve the solute, and add water to the volumetric line, seperately for each solution. If you need concentrations much lower than what you are saying, when weighing becomes your largest source of error, then it is more accurate to make a concentrated solution, and the dilute the concentrated solution. For example, you would use a class A TD (to deliver) volumetric pipette to measure the concentrated solution into a class A volumetric flask.

@DavePhD already gave a good description of how to prepare the solutions. Here are possible good reasons why the teacher doesn't like your original proposed method: distribute evenly does not work in practice (unless you mean: prepare a bit more, and then pipette 5 equal amounts).

But if you pipette, there is no reason not to pipette the amounts of stock solution that directly lead to the neeeded volume for the dilutions. Beaker is no volumetric glassware, and in addition not the preferred glassware for mixing (though mixing with magnet stirrer is OK). Volumetric flasks are much better: you can close them and then thorough mixing is possible. If you don't have volumentric flasks, Erlenmeyers are better than beakers. Would it be easier to dilute them by half each time That would lead to an exponential series of dilutions, like 1 mol/l, 0.1 mol/l, 0.01 mol/l etc.

Instead of the equispaced concentration series you describe. Also, serial dilution means that concentration errors build up: each dilution step adds error. Ultimately I will need 200ml of each solution With volumetric flasks, you can directly prepare 250 ml of each solution. Your proposed method would lead to varying volumes.

It is unlikely that the proper volumes are available as volumetric flask. Calculating the needed volumnes for the volumetric flask + pipetting stock solution or the graduated cylinder version is easy. A plausibility check of this can probably be done on the fly in the lab without calculator.

Calculating the needed additional volume for your method is somewhat more elaborate. This is of course a bad reason if it is only about laziness. But it is a good reason if it is about doing plausibility checks while doing lab work. Last possible reason: working with volumetric flasks thorough mixing is easier and the volume is anyways more precise than with a graduated cylinder.

(Far more precise if you are still learning the practical skills of lab work: with the graduated cylinder you neet to get both volumes right at the first attempt. With a pipette getting the volume right is much easier. So only the flask volume needs to be right at the first attempt - and the flask has a neck that helps with precise volumina.).

Overview Source: Laboratory of Dr. Jill Venton - University of Virginia Calibration curves are used to understand the instrumental response to an analyte and predict the concentration in an unknown sample. Generally, a set of standard samples are made at various concentrations with a range than includes the unknown of interest and the instrumental response at each concentration is recorded. For more accuracy and to understand the error, the response at each concentration can be repeated so an error bar is obtained. The data are then fit with a function so that unknown concentrations can be predicted. Typically the response is linear, however, a curve can be made with other functions as long as the function is known.

The calibration curve can be used to calculate the limit of detection and limit of quantitation. When making solutions for a calibration curve, each solution can be made separately. However, that can take a lot of starting material and be time consuming. Another method for making many different concentrations of a solution is to use serial dilutions. With serial dilutions, a concentrated sample is diluted down in a stepwise manner to make lower concentrations. The next sample is made from the previous dilution, and the dilution factor is often kept constant.

The advantage is that only one initial solution is needed. The disadvantage is that any errors in solution making—pipetting, massing, etc.—get propagated as more solutions are made. Thus, care must be taken when making the initial solution. Cite this Video JoVE Science Education Database. Analytical Chemistry.

Calibration Curves. JoVE, Cambridge, MA, (2019). Principles Calibration curves can be used to predict the concentration of an unknown sample.