What are common mistakes students make with molarity?
Molarity symbol is a uppercase m; M. (mol/L)
This can be often mistaken for the mass symbol, m (g), or the symbol for molar mass, which also M (g/mol).
The symbols are the same, the units aren't. This is why reading the question carefully is important.
Students also often rush through the question and not read it properly. If it says molarity or concentration, the units you are given are mol/L, not g/mol, or L/mol, etc.
They must not mistake the values that are given in the question, or they will make errors using dimensional analysis/unit analysis or using formulas.