An aqueous solution is 40.0% by mass hydrochloric acid, HCl, and has a density of 1.20 g/mL.
The molality of hydrochloric acid in the solution is m.
40% w/w HCl means 40g HCl in 100 g solution.
That is 40g HCl in (40g HCl + 60g H2O).
mols HCl in 40 g = 40/about 36.5 = about 1.1 but you need a more accurate number.
Then m = mols/kg solvent = 1.1mol/0.060kg solvent = ?m.
I think you need density to determine the molarity but not the molality.
An aqueous solution is 40.0 % by mass hydrochloric acid, HCl, and has a density of 1.20 g/mL.
The mole fraction of hydrochloric acid in the solution is
To find the molality of hydrochloric acid in the solution, we need to first convert the given mass percent into grams of HCl.
Let's assume we have 100 g of the solution, then the mass of HCl in the solution is 40.0 g (since it is 40.0% by mass).
Next, we need to calculate the moles of HCl. To do this, we need to know the molar mass of HCl. The molar mass of HCl is approximately 36.5 g/mol (the atomic mass of hydrogen is approximately 1 g/mol and the atomic mass of chlorine is approximately 35.5 g/mol).
Using the equation:
moles (n) = mass (m) / molar mass (M),
we can calculate the moles of HCl:
n = 40.0 g / 36.5 g/mol ≈ 1.10 mol.
Now, we need to find the mass of water in the solution. Since we assumed we have 100 g of the solution and the mass of HCl is 40.0 g, the mass of water is:
mass of water = 100 g - 40.0 g = 60.0 g.
Finally, we can calculate the molality (m) using the equation:
molality (m) = moles of solute / mass of solvent (in kg).
Since we have the moles of HCl (1.10 mol) and the mass of water (60.0 g), we need to convert the mass of water to kg (divide by 1000):
mass of water in kg = 60.0 g / 1000 = 0.060 kg.
Now we can calculate the molality:
molality (m) = 1.10 mol / 0.060 kg ≈ 18.3 mol/kg.
Therefore, the molality of hydrochloric acid in the solution is approximately 18.3 mol/kg.
To find the molality of hydrochloric acid in the solution, we need to determine the amount of hydrochloric acid in moles divided by the mass of the solvent in kilograms.
First, we need to calculate the mass of the hydrochloric acid in the solution. Since the solution is 40.0% by mass hydrochloric acid, we can assume we have 100g of solution. Therefore, the mass of the hydrochloric acid in the solution is 40.0g (40% of 100g).
Next, we need to convert the mass of hydrochloric acid to moles. To do this, we need to know the molar mass of HCl. The molar mass of HCl is approximately 36.5 g/mol (1 mol of hydrogen weighs 1 g, and 1 mol of chlorine weighs 35.5 g).
Now we can determine the number of moles of hydrochloric acid in the solution using the formula:
moles = mass / molar mass
moles = 40.0 g / 36.5 g/mol ≈ 1.10 mol
Next, we need to determine the mass of the solvent. Since the density of the solution is 1.20 g/mL, we know that 1 mL of the solution weighs 1.20 g. Therefore, the mass of 1000 mL (1 L) of the solution is 1200 g.
Finally, we can calculate the molality using the formula:
molality = moles of solute / mass of solvent in kg
molality = 1.10 mol / 1.20 kg ≈ 0.92 mol/kg
So, the molality of hydrochloric acid in the solution is approximately 0.92 mol/kg.