Science, Tech, Math › Science Molality and Concentration of a Chemical Solution Practice calculating molality with this sample problem Share Flipboard Email Print The concentration of sucrose in water may be expressed in terms of molality. Uwe Hermann Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated December 07, 2019 Molality is a means of expressing the concentration of a chemical solution. Here's an example problem to show you how to determine it: Sample Molality Problem A 4 g sugar cube (Sucrose: C12H22O11) is dissolved in a 350 ml teacup of 80 °C water. What is the molality of the sugar solution?Given: Density of water at 80° = 0.975 g/ml Solution Start with the definition of molality. Molality is the number of moles of solute per kilogram of solvent. Step 1 - Determine number of moles of sucrose in 4 g.Solute is 4 g of C12H22O11 C12H22O11 = (12)(12) + (1)(22) + (16)(11)C12H22O11 = 144 + 22 + 176C12H22O11 = 342 g/moldivide this amount into the size of the sample4 g /(342 g/mol) = 0.0117 mol Step 2 - Determine mass of solvent in kg. density = mass/volumemass = density x volumemass = 0.975 g/ml x 350 mlmass = 341.25 gmass = 0.341 kg Step 3 - Determine molality of the sugar solution. molality = molsolute / msolventmolality = 0.0117 mol / 0.341 kgmolality = 0.034 mol/kg Answer: The molality of the sugar solution is 0.034 mol/kg. Note: For aqueous solutions of covalent compounds—such as sugar—the molality and molarity of a chemical solution are comparable. In this situation, the molarity of a 4 g sugar cube in 350 ml of water would be 0.033 M.