A solution contains 5.00% (by mass)NaCl. The density of the solution is 1.064 g/cm^3. What is the molarity of NaCl?
5.00% w/w NaCl means 5.00 g NaCl per 100 g solution.
mols NaCl = grams/molar mass. Solve for mols NaCl.
mass soln = volume x density. Solve for volume and convert to L.
Finally, M = mols/L soln.
To find the molarity of NaCl in the solution, we need to first convert the percent by mass to grams of NaCl per liter of solution.
Step 1: Convert the percent by mass to a decimal.
5.00% = 5.00/100 = 0.0500
Step 2: Calculate the mass of NaCl in grams.
Since we don't know the total mass of the solution, we'll assume we have 100 grams of solution. Therefore, the mass of NaCl is:
0.0500 * 100 g = 5.00 g
Step 3: Calculate the volume of the solution.
Since the density of the solution is given, we can assume that 1 cm^3 of the solution has a mass of 1.064 g. Therefore, the volume of the solution is:
mass/volume = 5.00 g / 1.064 g/cm^3 = 4.69 cm^3
Step 4: Convert the volume to liters.
1 cm^3 = 1 mL, so 4.69 cm^3 = 4.69 mL
1 mL = 1/1000 L, so 4.69 mL = 4.69/1000 L = 0.00469 L
Step 5: Calculate the molarity.
Molarity (M) = moles of solute / volume of solution in liters
To find the moles of NaCl, we need to divide the mass by the molar mass of NaCl, which is 58.44 g/mol:
moles of NaCl = 5.00 g / 58.44 g/mol = 0.0856 mol
Molarity = 0.0856 mol / 0.00469 L = 18.27 M
Therefore, the molarity of NaCl in the solution is 18.27 M.