Calculate the molality (m) of CH2Cl2 in a solution generated by combining 846 g of the solute CH2Cl2 with 11.2 L of the solvent ethanol.
molality = moles solute/kg solvent. You can't go anywhere with this problem until you know the densities of the solute and solvent. You MAY be able to assume the density of water as 1.00 g/cc.
To calculate the molality (m), we first need to determine the number of moles of the solute and the mass of the solvent.
Step 1: Calculate the number of moles of the solute (CH2Cl2).
To do this, we need the molar mass of CH2Cl2, which can be found by adding up the atomic masses of carbon (C), hydrogen (H), and chlorine (Cl).
The atomic masses are:
C = 12.01 g/mol
H = 1.01 g/mol
Cl = 35.45 g/mol
Molar mass of CH2Cl2 = (12.01 g/mol × 1) + (1.01 g/mol × 2) + (35.45 g/mol × 2) = 84.93 g/mol
The number of moles of CH2Cl2 is calculated by dividing its mass by its molar mass:
Number of moles = Mass / Molar mass
Number of moles = 846 g / 84.93 g/mol = 9.961 mol (rounded to three decimal places)
Step 2: Calculate the mass of the solvent (ethanol) in kilograms.
First, convert the volume of ethanol from liters to kilograms. We need the density of ethanol for this conversion.
The density of ethanol is commonly listed as 0.789 g/mL or 0.789 kg/L.
Mass of ethanol = Volume of ethanol × Density
Mass of ethanol = 11.2 L × 0.789 kg/L = 8.8288 kg (rounded to four decimal places)
Step 3: Calculate molality (m).
Molality is defined as the number of moles of solute divided by the mass of the solvent in kilograms.
Molality (m) = Moles of solute / Mass of solvent (in kg)
Molality (m) = 9.961 mol / 8.8288 kg = 1.128 m (rounded to three decimal places)
Therefore, the molality of CH2Cl2 in the solution is approximately 1.128 m.