what is the molality of a solution of 50.0 grams of propanol in 152 mL water if the density of wate is 1.0 g/mL and the density of the solution is 0.78 g/mL
m = moles/kg solvent
moles propanol = g/molar mass propanol = ??.
m = ??moles/0.152
I am not sure what to do with the density of the solution of 0.78 g/mL.
The answer I came up with is 5.47 mol/kg. I found the density of the water in grams then I converted it to kg (152 x .001 = .152. I divided 50 g by the molar mass of 60.09502 g/mol = .8320 moles. Next, I divided that by .152. However, I didn't use the .78 g/mL beacause I am not sure what to do with it. Please explain.
5.47 molal is correct. You don't need the density of the solution.
To find the molality of a solution, we first need to determine the number of moles of the solute, in this case, propanol (C3H8O). Here's how you can calculate it:
1. Calculate the moles of propanol:
- Given mass of propanol = 50.0 grams
- Determine the molar mass of propanol by summing the atomic masses of each element:
- Carbon (C) atomic mass = 12.01 g/mol
- Hydrogen (H) atomic mass = 1.01 g/mol
- Oxygen (O) atomic mass = 16.00 g/mol
- Molar mass of propanol = (3 × C) + (8 × H) + O = (3 × 12.01) + (8 × 1.01) + 16.00 = 60.11 g/mol
- Calculate the moles of propanol using the formula:
- Moles = mass / molar mass
- Moles of propanol = 50.0 g / 60.11 g/mol
2. Next, we need to determine the mass of the solvent, which is water. We'll use the given density of water:
- Density of water = 1.0 g/mL
- Volume of water = 152 mL
- Mass of water = density × volume
3. Now, let's calculate the mass of the solution by adding the masses of propanol and water:
- Mass of solution = mass of propanol + mass of water
4. Finally, we can calculate the molality of the solution using the formula:
- Molality = moles of solute / mass of solvent (in kg)
- Mass of solvent needs to be converted to kg by dividing by 1000.
By following these steps, you can find the molality of the solution containing 50.0 grams of propanol in 152 mL of water.