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# freezing point depression experiment sources of error Shade, Ohio

Approximately 15 to 20 grams of naphthalene was added to the test tube. The substance would seem lighter than it is. 4. The apparatus should look as pictured below: PROCEDURES Part A Weigh a large test tube The first curve plots time versus temperature of pure naphthalene; the second curve plots time versus temperature of a solution of sulfur in naphthalene.

What mass of NaCl is dissolved in 150 g of water in a 0.050 m solution? .050 m = x mol / 150 g H20 x = 7.5 mol (7.5 mol)/(58.44 Since the solution is 28.0% NH3: 900 g × (.280) = 252 g NH3 per 900 g of solution. Please try the request again. Since the solution is 37.2% HCl: 1190 g × (.372) = 442.68 g HCl per 1190 g solution.

By using the incorrect value for the freezing point of the mixture, the calculated freezingÂ point depression would increase if the temperature used was too low, and would decrease if thetemperature used Insert the test tube into the beaker. When most of the naphthalene had melted, the stopper containing the thermometer and stirrer was placed into the test tube. Close NAME DATE Chemistry 1° Lab 19: Colligative Properties: Freezing-Point Depression and Molar Mass OBJECTIVES To become familiar with colligative properties To be able to use these properties to determine the

When molecular mass is calculated based on this, the calculated value for the molecularÂ mass of benzoic acid would decrease, because the number of grams present is being divided by alarger number These contaminates in the antifreeze could have raised or lower the freezing point depression from what it would have been with pure antifreeze. Colligative properties are properties of solutions that depend upon the number of solute particles to the number of solvent molecules in a solution. Make sure the thermometer is not resting or touching the sides of the test tube.

Sources of error One source of error for this lab is unwanted contaminants in the H2O used since the H2O was taken from the tap instead of using distilled water. Unfortunately these cooling curves are not available online. Thislarger molality of benzoic acid would then indicate more moles of benzoic acid present in thesolution. the freezing point A nonvolatile solute lowers the freezing point.

This would have caused the calculated molality to be too high. It was heated to about 85°C. The solvent boils when the vapor pressure, or tendency of solvent molecules to escape, is equivalent to the atmospheric pressure. The test tube containing solid solution was handed to the laboratory instructor for proper disposal of chemicals.

Record the mass in Data Table A. To determine the molecular mass of an unknown substance by finding the freezing point of two solutions (BHT and para-dichlorobenzene, and BHT and the unknown. Record temperatures until at least five values are constant (make note of when crystals form).6. This would indicate a smaller molality of benzoic acid thanthe actual value of the molality of benzoic acid of the solution.

The dissolution of a solute with very low vapor pressure, or a nonvolatile solute, raises the boiling point and lowers the freezing point. Loading presentation... Using a timepiece and the thermometer measure the room temperature every 30 seconds and record it in Data Table A under "Cooling-Curve data". Determination of the Molar Mass of Sulfur Mass of sulfur: 1.497 ± .001 g (weighing paper was tared) The sulfur was in powdered form.

When the vapor pressure of a solvent is equal to atmospheric pressure, the solvent boils. Report abuseTranscript of Molecular Mass by Freezing Point Depression LabMolecular Mass by Freezing Point Depression Prelab Purpose Graphs Conclusion 1. If the freezing point of the solution had been incorrectly read .3° lower than the true freezing point, then the observed ΔTf would have been greater than it should have been. Procedure: ► A.

All of these values will be determined experimentally. Bend the stirrer so the loop encircles the thermometer. Replace the test tube in the water bath and heat until all the naphthalene has melted. Antifreeze is a solution with a depressed freezing point.

The thermometer was not allowed to touch the bottom or sides of the test tube. Freezing point of pure naphthalene, from cooling curve. (Graphical interpolation.) = 80.4 ± .2 °C Freezing point of solution of sulfur in naphthalene, from cooling curve. (Graphical interpolation.) = 77.8°C ± When molecular mass is calculated based on this, the calculated value for the molecularÂ mass of benzoic acid would increase, because the number of grams present is being divided by asmaller number Place the stopper in the test tube.

The pressure of a solution is lower than the pressure of the pure substance because when a solute is present, the surface of the solution is comprised of solute particles and Also, take care because naphthalene is flammable. Another scientific concept used in this experiment was that of molar mass. Attach a test tube clamp above the ring on the ring stand.

A volatile substance ha a high vapor pressure and a nonvolatile substance has a low vapor pressure at room temperature. Remove from the water; Continuously stir and Record temperature every 20 seconds until there are six values after crystallization.9. Public Share Embed Liked Like Present Remotely Send the link below via email or IMCopy Present to your audienceStart remote presentationInvited audience members will follow you as you navigate and presentPeople