Final answer:
To calculate the molarity of a 38% HCl solution with a density of 1.20 g/mL, multiply the density by the volume to find the mass, calculate the mass of HCl using the percentage, convert this mass to moles using the molar mass of HCl, and divide by the volume in liters to find molarity.
Step-by-step explanation:
To find the molarity of a 38% HCl solution with a density of 1.20 g/mL, you first need to calculate the mass of HCl in one liter of solution. Since density is mass per volume, for a 1 L solution (which is 1000 mL), you have:
Mass of solution = 1.20 g/mL × 1000 mL = 1200 g
With the solution being 38% HCl by mass:
Mass of HCl = 38% of 1200 g = 0.38 × 1200 g = 456 g
Next, convert the mass of HCl to moles using its molar mass (36.5 g/mol):
Moles of HCl = 456 g × (1 mol HCl / 36.5 g HCl) = 12.493 mol
Finally, molarity (M) is defined as moles of solute per liter of solution. Therefore, the molarity of the HCl solution is:
Molarity = 12.493 mol / 1 L = 12.493 M