25g of magnesium chloride (MgCl2) was dissolved in 250 ml distilled water at 25oC. The density of water was 0.9975g/cm3. Calculate the concentration in molality
To calculate the concentration in molality, we need to follow these steps:
Step 1: Calculate the mass of water in grams.
Given:
- Volume of water (V) = 250 ml = 250 cm³
- Density of water = 0.9975 g/cm³
Mass of water (Mw) = Density × Volume
Mw = 0.9975 g/cm³ × 250 cm³
Mw = 249.375 g
Step 2: Calculate the moles of magnesium chloride (MgCl₂).
Given:
- Mass of magnesium chloride (MgCl₂) = 25 g
- Molar mass of MgCl₂ = 95.211 g/mol
Moles of MgCl₂ = Mass / Molar mass
Moles of MgCl₂ = 25 g / 95.211 g/mol
Moles of MgCl₂ = 0.2627 mol
Step 3: Calculate the molality.
Molality (m) = Moles of solute / Mass of solvent (in kg)
Mass of solvent = Mass of water / 1000 (since it needs to be in kg)
Mass of solvent = 249.375 g / 1000
Mass of solvent = 0.249375 kg
Molality (m) = 0.2627 mol / 0.249375 kg
Molality = 1.054 mol/kg
Therefore, the concentration of the magnesium chloride solution is 1.054 mol/kg.
You have .250 liters of solute, or 250ml*.9975g/ml or .250*.9975 kg solute
You have 25/95.211 moles magnesium chloride.
molality= moles Chloride/kg of solute
do the math