25g NaOH is dissolved in 10 ml h20 and added to 100 ml volumetric flask. Calculate the concentration in molarity.

Answer 1

M = mols/L (that's the definition--start with that).
Then mols = grams/molar mass = ? and I'll estimate that at approx 25/40 = about 0.5 mol (remember this is only close so yo need to redo the math to obtain a more accurate answer).
M = mols/L. You know mols and you know L.
I don't know if this is a trick question or not but it is stated in a weird way. First, if you dissolve 25 g NaOH in 10 mL water the total volume is NOT 10 mL. If the author intended you to use mols/L then you would have approx 0.5/0.01 BUT since the volume is not 10 mL it would not be right. Second, there is nothing in the problem about adding water to the mark of the volumetric flask to make 100 mL. If the author intended that to be the problem the M = approx 0.5/0.100 = ? but the way the problem is stated that isn't the problem.