When is molality used

What is the molality when If I have 2. What's the molality? See all questions in Molality. Impact of this question views around the world. Facebook Facebook Twitter Twitter. Updated December 07, Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. What is the Difference Between Molarity and Molality?

Calculating Concentrations with Units and Dilutions. Calculating the Concentration of a Chemical Solution. Molality and Concentration of a Chemical Solution. Freezing Point Depression Example Problem. The Difference Between Molality and Molarity. Convert grams of glucose to moles and divide by the mass of the water in kilograms. Step 3: Think about your result. The answer represents the moles of glucose per kilogram of water and has three significant figures.

Molality and molarity are closely related in value for dilute aqueous solutions because the density of those solutions is relatively close to 1. This means that 1. As the solution becomes more concentrated, its density will not be as close to 1. For solutions with solvents other than water, the molality will be very different than the molarity.

Make sure that you are paying attention to which quantity is being used in a given problem. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. Molality and molarity are both concentration terms. Given molarity's popularity molality seems rather antiquated. Why is molality still discused in modern chemistry classes?

One of the key attractions of molality is that changing the temperature of a solution does not change the molality, while it may change the molarity. The downside, of course, is that the amount of solute required to reach a given molality depends on the nature of the solvent; ambiguity may also arise when a mixed solvent system e.

As for why it's introduced in school , that's a pedagogical question beyond the scope of this answer, but both molarity and molality have their uses in the laboratory. Molality could be determined with respect to only the water, or the combined water-ethanol solution, leading to different calculated concentrations. In addition to JSK's excellent answer, I'd like to point out that there's a common pitfall related to molarity which JSKs answer might have slipped on : molarity is defined as amount of substance of solute per liter of solution , while molality is amount of substance of solute per kilogram of solvent.

This might not seem like a huge difference, but if you have a highly concentrated solution, you can sometimes get pretty big discrepancies between the volume of solvent and volume of solution.