Question

A solution of concentrated NaOH is 16.7M. If the density of the solution is 1.02 g/mL, what is the percent by mass of NaOH?

I have tried different calculations and molarity and % but im not catching on at all

Answer 1

I have always used this one. Works every time.
1.02 g/mL x 1000 mL x (%/100) x (1/molar mass NaOH) = M

You can do it piecemeal if you wish.
M = mols/L. You know M and 1L, solve for mols.
grams NaOH = mols x molar mass gives you grams solute.
density of the 1 L gives you grams of the solution.
(grams solute/grams solution)*100 = %