bio_chem

I'm a little stuck on a problem that requires me to explain how I would use the process of serial dilution to create solutions of 0.05mM, 0.10mM, 0.25mM, 0.5mM, and 1.5mM from a stock solution of 10mM. Normally, I see problems where the ratio between the solutions is equal, so you would basically take, for ex. 1mL from the stock, and mix it with 9mL of water, and repeat this process for the following dilutions. In this case, however, the ratios between the solutions are not equal (0.10mM is twice that of 0.05mM, while 0.25mM is 2.5 that of 0.10mM). If the ratios aren't equal between the solutions to prepare, then how should one go about using serial dilution? Any help would be much appreciated!