Final answer:
The molarity of a solution made by dissolving 15.0 grams of NaOH in 200.0 mL of water is 1.875 M.
Step-by-step explanation:
To find the molarity of a solution, we need to know two things: the amount of solute (in this case NaOH) in moles and the volume of the solution in liters. First, we convert the mass of NaOH to moles by using the molecular weight of NaOH (which is approximately 40.00 g/mol).
Number of moles = Mass (g) ÷ Molecular weight (g/mol) = 15.0 g ÷ 40.00 g/mol = 0.375 moles
Next, we convert the volume of water from milliliters to liters. Remember that there are 1000 milliliters in 1 liter.
Volume in liters = 200.0 mL × (1 L ÷ 1000 mL) = 0.200 L
Finally, we divide the number of moles by the volume in liters to get the molarity of the solution.
Molarity = Moles of solute ÷ Volume of solution in liters = 0.375 moles ÷ 0.200 L = 1.875 M