Treatment of 1.385 g of an unknown metal M with an excess of aqueous HCl evolved a gas that was found to have a volume of 382.6 mL at 20.0 °C and 755 mm Hg pressure. Heating the reaction mixture to evaporate the water and remaining HCl then gave a white crystalline compound, MClx. After dis- solving the compound in 25.0 g of water, the melting point of the resulting solution was - 3.53 °C. (c) What is the molality of particles (ions) in the solution of MClx?

Video transcript

Hello. In this problem, we are told a 1.4 to 3 g chunk of an unknown metal was dissolved in excess hydrochloric acid. The volume of evolved hydrogen gas was major to B four and 65 mL at degrees Celsius and 230.955 atmospheres. When the reaction mixture was heated to drive off excess hydrochloric acid and water. A colorless crystalline solid was obtained. The solid was then re dissolved in 45 g of water. To make clear solution. The freezing point of the solution was measured as -2.35°C. We are asked to calculate the total morality of particles in the metal chloride solution. So there's a lot of information provided in the problem statement that we don't need to solve the problem. We are asked to find the total morality of ions or particles in the middle chloride solution. Total morality is equal to the osmolarity, which is equal to the Van Hoff factor times the morality we can make use of the depression of freezing point for a solution formula, which is given by the change in the freezing point is equal to the Vantaa factor times a freezing point. Depression constant, times the morality are metal chloride was dissolved in water. So water is our Sullivan water has a freezing point. Depression constant at 1.86 degrees Celsius per morale. The change in the freezing point is equal to the freezing point of pure water Minour that of the solution freezing point of pure water is 0°C And we were told the freezing point of the solution was measured as -2.35°C. The change in freezing point then is 2.35 three Celsius. We can take our formula above and solve for oz morality. To obtain osmolarity would take change in the freezing point and divide by the freezing point depression constant. The change in the freezing point was found to be 2.35 to be Celsius, and the freezing point depression constant is 1.86 degrees Celsius Permal al are units of degrees Celsius cancels. This works out to 1.26 mol al. You can also write out the as morality as 1. moles of ions per kilogram of our solvent, which is water. So in this problem we are asked to find the total morality of particles or ions in the middle chloride solution and we found the osmolarity to be equal to 1.26 mol al, or moles of ions per kilogram of water. Thanks for watching. Hope This helped