Answer:
1.93 molar, or M
Step-by-step explanation:
By definition, molarity is defined as moles/liter. A 0.5 molar (or M) solution will have 0.5 moles of solute per 1.0 liter. To answer this question, first calculate how many moles of NaOH there are in 11.6 grams of the compound. We'll need the miolar mass of NaOH, which is 40 grams/mole. This is found by adding the atomic masses of each atom in the compound:
Na: 23
O: 16
H: 1
Total: 40 g/mole
The moles of NaOH is found by dividing the mass by the molar mass:
(11.6 grams NaOH)/(40 g/mole NaOH) = 0.29 moles NaOH
0.29 moles NaOH is contained in 15cm^3 of solution. Convert 15cm^3 into liters (L):
(15 cm^3)*(1 ml/cm^3)*(1 liter/1000 ml) = 0.015 liters
cm^3 and ml both cancel with these conversion factors, leaving only liters, L.
The solution consists of 0.29 moles of NaOH in 0.15L. It's concentration is therefore:
(0.29 moles)/(0.015L) = 1.93 molar, or M