After my calculations, I have arrived at the value of 1833. Using these equations, such as density and number of moles n , we can substitute different values into the ideal gas law to manipulate it. Some of these properties include vapor pressure lowering, boiling-point elevation, freezing point lowering, and osmotic pressure. Have you made any changes to the procedure? Remove the hot water bath as before, and dry off the outside of the test tube using a paper towel. Materials: test tube, Thermometer, 10 mL graduated cylinder, 2 micropipettes, Styrofoam cups, 4 pieces plastic wrap, 70% ethyl rubbing alcohol, 91% isopropyl rubbing alcohol, ice, distilled water, rock salt Procedure: Using the graduated cylinder, measure 2 mL of alcohol and pour it into the test tube. It was too deep in the substance, so when we re-heated it after it had solidified, the test tube expanded until it broke.
This limits the significant figures because the temperature readings were only rounded to one significant figure. Amount of substance, Concentration, Equivalence point 602 Words 3 Pages The Ka and Molar Mass of a Monoprotic Weak Acid Chemistry Lab 152 Professor: James Giles November 7, 2012 Abstract: The purpose of this experiment was to determine the pKa, Ka, and molar mass of an unknown acid 14. Part 1: Determination of K f for Cyclohexane The freezing point must be within the temperature range spanned by your solutions of known solute molality. The amount of the freezing point depression can be. This will cause the freezing point to continue decrease after the constant temperature. Select answers are provided for you in red.
Introduction There are two types of mixtures; homogenous and heterogeneous. A weighed amount of the solute substance X is dissolved in a known mass of solvent naphthalene. By not measuring substances accurately, the calculations could be a bit off. This freezing process releases a quantity of heat energy that is equal in magnitude but opposite in sign to the heat of fusion, Δ H fusion, of the substance. Atmospheric pressure, Boiling point, Gas 1201 Words 4 Pages Ghazali Ahmad Dec. What is the molar mass of the unknown substance? The ideal gas law compares four properties of a gas which include pressure, volume, moles, and temperature.
From the results obtained in the experiment, it obeys the theory of freezing point depression stating that the solution which contains naphthalene and substance X will have lower freezing point compared to the freezing point which contains only pure solvent naphthalene. Immediately turn it in to the stockroom for disposal. Attach your three graphs to this report. The molar mass would not be affected because the change in temperature would always be the same. When a small amount of nonvolatile solute is dissolved in a volatile solvent, the vapor pressure of the solvent over the solution will be less than the vapor pressure of the pure solvent at the same temperature. Colligative properties are physical properties of solutions that depend upon the number but not the kind of solute particles present. The lightest possible chemical that one can have under normal conditions is hydrogen gas, or H2.
Knowing the equations above, and the data from our observations, we can solve for the molar mass of the unknown. Each graph should have an appropriate title and labeled axes with an appropriate scale. This effect is known as colligative property. Lab 7 - Determination of the Molar Mass of an Unknown Solid by Freezing Point Depression Goal and Overview In the first part of the lab, a series of solutions will be made in order to determine the freezing point depression constant, K f, for cyclohexane. Therefore, an aqueous solution containing 1.
. Colligative properties, Freezing, Freezing-point depression 763 Words 5 Pages The melting point is the temperature at which the crystal structure of a solid breaks down with increasing entropy +ΔS. The freezing point depression can be explained as solvent molecules leaves the liquid phase and join to form the solid phase; they leave behind a lesser volume of solution where the solute particles may present. The fact that these two phases are in equilibrium does not mean that molecules are not passing from one phase to the other. Chemistry, Concentration, Freezing-point depression 491 Words 24 Pages Chemistry 121 Experiment 19 Molar Mass Determination y Depression of the Freezing Point Introduction: The most commonly used liquid is water. Key Terms: List and define any additional new terms relevant to this experiment.
This is known as freezing point depression. This value divided by the molality, which has the units of moles of the solute divided by the mass of the solvent, can determine the molar mass since the kg units cancel each other out, and only the grams over mole units are left. Clamp the test tube in the beaker and insert the thermometer and stirring wire assembly into the test tube and clamp the assembly to the ring stand. Do not weigh out the p-dichlorobenzene in advance of using it because it is a volatile solid it sublimes quite rapidly. Every liquid has a freezing point: the temperature at which a liquid undergoes a phase change from liquid to solid. Since the substances are not soluble in water, the van't Hoff factor, i, would equal 1 because insoluble substances in water do not dissociate. The students used the freezing point depression to find the molar mass of benzoic acid.
Using Fiji bottle water, the most purest water available, would fix this error. An ice bath was prepared by filling a 600mL beaker ¾ full of ice and covered with ¼ to. The freezing point of a solvent Cyclohexane was determined, and compare to the freezing point of Cyclohexane with the addition of two different concentration of unknown solid. While there are various colligative properties such as the burning point, vapor pressure, and osmotic pressure, in this experiment freezing point depression is used to find the molar mass of the unknown solute. Molar mass is useful to identifying an unknown substance; methods such as using finding the freezing point depression of an unknown substance can help in finding the identity.
Chemical properties tell us how the substance. The temperature at the point of intersection is the solvent freezing point and should be clearly shown on each graph. Freezing-point depression, Liquid, Melting point 602 Words 2 Pages Calculations For this experiment, the osmolality given by the machine was equal to the molality. As the solid begins to form, the system remains at a constant temperature until the melt is completely converted to solid. Label them with the contents, your name, and your section. The eutectic composition is that at which two solids crystallize out in a ratio equal to that of the melt, and the cooling curve obtained would have the same characteristics as that of a pure substance.