mass of methanal = -350.0 g
This result is still negative, which means that the given information cannot be correct.
We are given a 0.75 molal solution of methanal (also known as formaldehyde) dissolved in water, and we are told that the total mass of the solution is 650.0 g. We need to calculate the mass of methanal in this solution.
Assuming this information, we can proceed with the calculation as follows:
The molar mass of methanal (HCHO) is 30.03 g/mol. A 0.75 molal solution of methanal means that 0.75 moles of methanal are dissolved in 1 kg of water.
First, we need to calculate the mass of water in the solution. We can use the molality formula to do this:
molality = moles of solute / mass of solvent (in kg)
0.75 molal solution means 0.75 moles of methanal are dissolved in 1 kg of water.
Therefore, the amount of water in the solution is:
moles of methanal = 0.75 mol
mass of water = moles of methanal / molality = 0.75 mol / 0.75 mol/kg = 1 kg
Since the total mass of the solution is 650.0 g, the mass of methanal can be found by subtracting the mass of water from the total mass:
mass of methanal = total mass of solution - mass of water
mass of methanal = 650.0 g - 1000 g
mass of methanal = -350.0 g
This result is still negative, which means that the given information cannot be correct.