A solution is made by dissolving 82.81dg of potassium hydroxide, KOH, in 0.1707kg of water. What is the mass percentage of solute in this solution? Key Concept: Solution concentration is often measured as a weight fraction of solute, i.e. the weight of solute divided by the weight of the solution. It can be expessed as \%, ppm, ppb by multiplying the mass ratio by 100,106, or 109 respectively. Solution: The vapor pressure of pure water at 99A^C is normally 733.2mmHg, but decreased to 697.0mmHg upon addition of an unknown amount of sodium hypochlorite, NaOCl, to 288.1g of water at this temperature. How many grams of sodium hypochlorite were added? Assume complete dissociation of solute. Key Concept: Colligative properties - vapor pressure lowering in the presence of an ionic salt. Strategy: This following Raoult's law P=P0Xsolvent where Xsolvent=nsolvent/(insolute+nsolvent). 1. Use the two vapor pressures to figure out the mole fraction of solvent. 2. Determine the moles of H2O and substitute into definition of mole fraction of the solvent. 3. Solve for moles of solute and determine mass using the molecular weight. What is the van't Hoff factor of a compound that has a osmotic pressure of 4512 torr at 25.0A^C and a concentration of 0.1541M ? Key Concept: Henry's law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the solution, Sgas=kHP gas. Solution: 1. Rearrange the above equation so that the Henry's law constant is on one side and the rest is on the other side. 2. Since the units are M/atm. Convert the pressure from torr to atm. 3. Convert the solubility from g/L to moles/L using the molecular weight. 4. Substitute into rearranged Henry's law equation to determine the