A 25.0-g sample of sodium hydroxide is dissolved in 400.mL of water. What is the concentration of the solution?

Question

DrRebel · Accepted Answer

[NaOH] = [(25g)/(40g/mole)]/(0.400Liters) = 1.56M

DrBob222 · Answer

In what? % w/w; % w/v, mole fraction, M, m......? If you want it in m, then mols = grams/molar mass = ? Then m = mols NaOH/kg solvent. You can't do % w/v or M.

DrBob222 · Answer

The primary reason I said M was not possible is because that definition is mols/L SOLUTION. Your problem gives 400 mL water which is not the same as 400 mL solution. 25 g NaOH + 400 mL water is not 400 mL solution but more than that. By what volume who knows. So you may calculate m but not M.