Colligative Properties Report PDF

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Colligative properties report...

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Victoria Kieffer Chem-C 126 Section 22706 Colligative Properties Introduction The properties of solutions that are affected by the presence of solutes are known as colligative properties. Colligative properties are vapor pressure, osmotic pressure, freezing point, and boiling point. These effects rely on the physical presence of an amount of solute, rather than the type of solute. The solute’s particles interfere with the solvent’s ability to enter the vapor pressure phase when a nonvolatile solute is added into a solution. The vapor pressure of a solution would require a higher temperature to have the same vapor pressure as the pure solvent. Osmotic pressure is the pressure required to prevent the movement of solvent particles across a semipermeable membrane. The osmotic pressure will increase because the particles get in the way of osmosis occurring. Since it is known that more energy is required to cause the same vapor pressure, it can be assumed that the boiling point of a substance will be higher. Boiling will occur if the vapor pressure equals atmospheric pressure. In a solution, the solute particles are physically in the way and cause a higher amount of energy to be released for the solution to freeze. Thus, the freezing point is lowered. These four properties can be used to describe solutions. The purpose of this experiment is to observe the effects of a dissolved substance on the colligative properties of solutions. Discussion The following equation was used 1). The constant in this equation is kb. Molality will be used for the concentration and i represents the Van’t Hoff factor.

1) ∆ Tb=ikbm The kb of water was determined to be 0.54℃ /m. The Van’t Hoff was 2, with this to the molarity for the mass of NaCl. ∆ Tb was found by taking the difference between the two boiling points, 105.0 ℃ and 101.0℃ . To calculate the molar mass of ethylene glycol, the same equation was just rearranged to find the molar mass. The kb was 0.54℃ /m and the Van’t Hoff factor were 1. ∆ Tb was found by taking the boiling point of the ethylene glycol, 105.0 ℃ , and subtracting it from the boiling point of water, 101.0℃ . The molar mass was found to be 67.82 g/mol. The molar mass of the unknown substance was 40.12 g/mol. The error for the ethylene glycol was found to be 9.26 % with 2) equation. 2)

(measured molar mass −actual molar mass) ×100 actual molar mass

Conclusion In this experiment, the colligative properties of the boiling point were observed and recorded for water, NaCl, ethylene glycol, and an unknown substance. It was seen that a nonvolatile solute can affect the boiling point of a solvent. De-icing roads and sidewalks and using ethylene glycol as “anti-freeze” in car radiators, are real life events that decrease the freezing point....