What molarity is 15% NaOH made up in 100 ml i.e 15%w/v?
There is often some confusion over the meanings of the various measures of the concentrations of solutions. The weight to volume ratio w/v is generally defined as the weight of solute (in grams) divided by the volume of the solution (in ml or metric equivalent). The percentage weight to volume (%w/v) is more specifically the weight of solute in 100 ml of solution. The solution in question here thus has 15 g of NaOH in 100 ml of solution. As the molar mass of NaOH is very close to 40, this means that one litre (or 1 dm^3) of solution would contain (15/40) x 10 moles of NaOH, that is, it is 3.75 M. This is quite concentrated, more likely to be used to take the paint off your window frames than as a reagent in the lab. It’s also quite caustic, so there are safety considerations in its use.
