Molar Mass of a Solid Essay

AbstractThe purpose of this experiment is to determine the counterspyar weed of an obscure hard. The frost send of a settlement (Cyclohexane) was determined, and compare to the freezing focus of Cyclohexane with the join onition of two distinct concentration of unknown unwavering. The arrant(a) substance of Cyclohexane has defined physical properties. However, when a solute is added these properties are determined by the add of solute added, also known as colligative properties. The temperature of the freezing point was let down when the solid was added and it decreased as the concentration of the solid increased. The molality of the solute was determined, which was and then used to calculate the zep circumstances of the solid for two rivulets. An bonny of the poor boy sens of the unknown solid was measured to be 286.87+1.796g/mol with a %RSD of 0.626%. The purpose of the experiment was to obtain the molar clutch of an unknown solid.The molar mass is determine d by dissolving the unknown heighten into a pure eloquent with defined physical properties, in this study Cyclohexane. When dissolving a solute, it forms a homogeneous firmness of purpose, in which the closure of the solution physical properties are not longer defined, but depends on the amount of solute added. Whenever a substance is dissolved in a solvent, the vapor jam decreases. When the vapor contract decreases, it also lowers the boiling and freezing point of the solvent and increases the osmotic pressure. These four properties are known as the colligative properties, the magnitude of the changes depends on the amount of solute dissolve the changes are promptly proportional to each other. The high the solute concentration, the higher the changes of vapor pressure, therefore, a lower freezing point. It is hypothesized that the freezing point temperature will decreased, if there is a higher concentration of the solid added to the soution. drying up pressure is thepress ure exerted by a vapor when the vapor is in a state of dynamic equilibrium with its liquid. When a nonvolatilisable solute is dissolves in the solvent, solute molecules occupy a part of the surface area.This allows molecules into the vapor state, lowing the vapor pressure of the solvent. When the vapor pressure lowers, the boiling point elevates, due to the presence of the solute. Solute added to the solvent affects the freezing point, the energy of the solvent lowers to increase the magnitude of the intermolecular forces for the molecules to work over together to form a solid. The colligative properties are useful for determining molar masses of unknown nonvolatile solute. At low concentrations of a nonvolatile solute, the freezingpoint of depression of a solvent back be determine by Tf = Kf (solvent) -Tf (solution) = Kf m. Changes in freezing point Tf are directly proportional to the molality, m, of the solute in solution (molality, m = mol solute/ kg solvent). The freezing-poi nt constant, Kf for Cyclohexane is 20C k/mol, which is used to obtain the amount of moles of solute in the solution, which is reciprocally proportional to the change of freezing point Tf.The molal mass obtained is substantial to obtain the molar mass of the unknown solid (solute). The molal mass shows the unknown amount of moles of solute are need it per kilogram of solvent. Acquiring the human activity of moles of solute and analyzing it with the grams of solute measured in the laboratory obtaining the molar mass of the unknown solute.i The modify behavior of a solution different from a pure liquid solution when a solute its added. Te temperature at which the solution begins to freezing is lower than the pure solvent. The freezing point also lowers when there is a higher concentration of solute added to the solution. The molar mass of unknown solid can be determined by any of the colligative properties, the freezing point is not an exception and by knowing the mass of solute a nd temperature of the freezing point, the molar mass can be obtained.DiscussionThe freezing point depression is a colligative property of solutions, which is based only on the amount of solute added and not the defined chemical and physical properties of the substance. The freezing point of Cyclohexane observed was 4.97C, from the temperature reduction abridge (Figure 1). Freezing point values of Trial 1 and Trial 2 were collected, to compared to the freezing point of Cyclohexane and determine he depression of the solute. The unknown solid yielded a freezing depression of 3.64C for streamlet 1, and 2.84C for trial 2 (Figure 2 & 3). These values were compared to the original mass of unknown solute added to the Cyclohexane and the think molar mass ofthe unknown solid.The molar mass that was calculated for trial 1 was 288.14-g/mol, while trial 2 was 285.60-g/mol (Table 3). The average of the molar mass was calculated, and the molar mass of the unknown solid observed was around 286. 87-g/mol. When calculating the standard deviation was obtain only +1.796g/mol when examine some(prenominal) trials to the mean. The values are apparently close up together, make them highly precise, however, is unknown if the values are accurate, the unknown solid authentic molar mass still unknown. The relative standard deviation portion, obtained was 0.626% (Table 3) this meter expresses precision of the data, the smaller RSD the greater the precision for the average value of the data.The %RSD, is super low, making it the results a tremendously precise data of the mean. However, there was a possible error that could have affected the results. The error occurred during recording the cooling temperature of trial 1, the ice melted and the test tube was removed to add more ice into the beaker. Also, while recording the temperature of the Cyclohexane upon addition of unknown solid, the savor was not stir and therefore the value could have probably been invalid. changeless stir ring of solution would have assured an even mix of the solute particles and a more accurate freezing point. These small errors could have affected both trials creating a higher observed molar mass value for both trials.ConclusionThe experiment allowed for the determination of freezing point of Cyclohexane based on a logger pro software with calibrated thermometers to be close to 4.97C (Table 1). Freezing point depression was observed when two trials of different concentration of the unknown solid were added to the Cyclohexane. As the concentration of the unknown solid increased, the freezing point of the solution was also lowered (Table 2). As seen on Figure 4, when placing all three graphs it is visible, when solute is added a lower freezing point is observed. Using experimental measurements, the molar mass of the unknown solid was calculated to be 286.87+1.796g/mol. Based on the relative standard deviation percent (%RSD) of 0.626%, shows a highly precise measurements of unknown s olid molar mass when compared to the mean values.