Answering questions 237 and 238 based on the model 67. Model 67 Guiding questions

Model 67:Concentration UnitsSome concentration units depend on the temperature and some do not. Since liquids changevolume with temperature, concentration units based on volume are temperature dependent.Molarity (M): Moles of solute present per liter of solution.Molarity =moles of soluteliters of solution. When working molarity problems and no volume is specified, it is convenient to assume 1 L.Molality (m): Moles of solute per kilograms of solvent.Molality =moles of solutekilograms of solvent. When working molality problems and no amount of solvent is specified, it is convenient toassume 1 kg.Mass Percent (w/w) or Mass%: Ratio of solute mass and solvent mass expressed as a percentagePercentby mass =-mass of solutemass of solutionx 100When working percent by mass problems and no amount of solution is specified, it isconvenient to assume 100 g of solution.Mole Fraction (Xsubstance): Ratio of the moles of a given substance to the total number of molespresent in solution.X substancemoles of a given substancetotal number of moles in solution. When working mole fraction problems and no total number of moles in solution is specified.is convenient to assume 1 mole total.Density: Ratio of mass of solution to volume of solution (g/ml)density =mass of solutionvolume of solution