Question

I got NaOH 7%, its density is 1,08g/ml.
Calculate the molar concentration

Answer 1

7% means 7g NaOH in 100 g soln.
7g = how many mols? mols = g/molar mass

What is the volume? Calculate that from density. mass = volume x density.
Then M = mols/L

Answer 2

so then you say i need to do this,
volume=mass/destiny ---> 7(g)/1,08(g/ml)=7(ml)-->0,007(L)
and mols are ---> 7(g)/40(g/mols)=0,175(mol)

and then
0,175(mol)/0,007(L)=25(mols/L)?

Answer 3

Not quite.
You want mols/L for molarity. mols NaOH = 7g/molar mass NaOH = ?
Then the 100 g soln is the part that needs to be converted to L.
volume = mass/density = 100g/1.08 = 92.6 mL which is 0.0926 L.
Then M = mols NaOH/L soln.