The density of a 40.0% by weight aqueous solution of NaOH is 1.432 g/cm3 what is the molarity of NaOH?
To find the molarity (M) of NaOH in the solution, we need to first calculate the number of moles of NaOH present in 1 liter of the solution (mol/L).
To calculate the molarity, we need two pieces of information: the mass of NaOH and the volume of the solution.
Step 1: Find the mass of NaOH present in 1 liter of the solution.
Given that the solution is 40.0% by weight, it means for every 100 grams of the solution, 40 grams is NaOH.
Therefore, the mass of NaOH in 1 liter of the solution is:
40 grams / 100 grams = 0.4 * 1000 mL = 400 grams
Step 2: Calculate the moles of NaOH.
To find the number of moles, we need to divide the mass (in grams) by the molar mass of NaOH.
The molar mass of NaOH can be calculated as follows:
Na: atomic mass = 22.99 g/mol
O: atomic mass = 16.00 g/mol
H: atomic mass = 1.01 g/mol
So the molar mass of NaOH is:
22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 40.00 g/mol
Now, divide the mass of NaOH in the solution (400 grams) by the molar mass (40.00 g/mol) to get the number of moles of NaOH:
400 grams / 40.00 g/mol = 10 moles
Step 3: Find the molarity (M).
The molarity (M) is defined as the number of moles of solute (NaOH) divided by the volume of the solution in liters.
Since we now have the moles of NaOH (10 moles) and the volume of the solution is given as 1 liter, we can calculate the molarity:
Molarity (M) = Moles (mol) / Volume (L) = 10 mol / 1 L = 10 M
Therefore, the molarity of NaOH in the given solution is 10 M.