Which of the following can be determined if the boiling-point elevation, the mass of solute and the molality of a given solution are known.

The identity of the solute
The polarity of the solute
The size of a molecule of the solute The molecular weight of the solute

My answer: the molecular weight of solute
Reason: m= (mass of solute/M.M. solute)/(kg solvent)
But- I don't know how I'd be able to get the mass of the solvent. Is it possible for me to assume the solvent to be 1 L and convert that to kg?

I think molar mass is the right answer. No, you may not assume the solvent is 1 L and that the density is 1 kg; however, you can assume you have a kg of solvent, that will tell you the moles of solute. And if the delta T is known, the problem must tell you, also, the mass of the solvent. Or if this is a problem and you are trying to work it in parts and you have posted just pieces of the problem, I suggest you post the entire problem as a new post.

To determine the molecular weight of the solute, you're correct in using the equation: m = (mass of solute / M.M. solute) / (kg solvent). In order to calculate the molality (m), you would need to know the mass of the solute and the mass of the solvent.

To determine the mass of the solvent, you can assume it to be 1 liter (L) and convert it to kilograms (kg) by using the density of the solvent. The density of a substance is defined as its mass per unit volume. So, if you know the density of the solvent, you can convert the volume (1 L) to mass (kg).

For example, let's say you have water as the solvent. The density of water is approximately 1 g/mL at room temperature. Since 1 L is equal to 1000 mL, the mass of 1 liter of water would be 1000 grams (g). To convert grams to kilograms, you divide by 1000, resulting in 1 kilogram (kg) of water.

However, it's important to note that the mass of the solvent may vary depending on the specific conditions and the identity of the solvent being used. It is best to refer to the specific experimental conditions given or consult a reliable source for the appropriate mass of the solvent.

Once you have the mass of the solute and the mass of the solvent (converted to kg), you can use the molality equation to calculate the molecular weight of the solute.