I am still having a little problem with my original question. However, this is what I have done so far.
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.
ORIGINAL QUESTION - 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
I answered this for you last night just before retiring to bed. You don't need the 0.78 g/mL density of the solution. The answer is 5.47 molal. The question was to determine the molality of the solution; 5.47 m (mol/kg is molality) is the correct answer.
i have this question for an online assignment and it keeps telling me that 5.47 is wrong. so my guess is that you do need the density...just saying
To find the molality of a solution, you need to determine the moles of solute (propanol) and the mass of the solvent (water). Here's how you can calculate it:
Step 1: Determine the moles of propanol
To find the moles of propanol, divide the mass of propanol by its molar mass. The molar mass of propanol (C3H7OH) is approximately 60.09502 g/mol. Thus:
moles of propanol = (50.0 g) / (60.09502 g/mol) = 0.8320 mol
Step 2: Determine the mass of water
The density of water is given as 1.0 g/mL, and the volume of water is 152 mL. Therefore, the mass of water can be calculated by multiplying the volume of water by its density:
mass of water = (152 mL) * (1.0 g/mL) = 152 g
Step 3: Calculate the molality
Molality is defined as moles of solute per kilogram of solvent. To find the molality, divide the moles of propanol by the mass of water in kilograms:
molality = (0.8320 mol) / (152 g / 1000) = 5.47 mol/kg
Therefore, based on your calculations, the molality of the solution is indeed 5.47 mol/kg.
The density of the solution is not directly used to calculate molality. It is mentioned to provide information about the density of the solution compared to that of water. However, it is not necessary for finding the molality.