[gt5hz]

Let's say the subtance being referred to was prepared by a senior high school chem teacher or even chemists.

I know that it is equal to number moles/volume solution, so therefore it comes from measured values. But can 0.2M of say Fe(NO₃)₃ be written as 0.20M for the purpose of making the value more specific for calculations involving significant digits? Can I not assume that chemists/the teacher did a precise job of making it and say 0.20M instead of 0.2M?

[Borek]

If it is written as 0.2 M it is usually understood that concentration can be anything between 0.15 and 0.2499999, while 0.20M means anything between 0.195 and 0.204999999. Labelling 0.2M solution as 0.20M solution is an error.