1. Describe errors in procedure that may cause an observed capillary melting point of a pure compound 1. To be lower than the correct melting point The sample has impurities, the thermometer is not calibrated, or failure to properly clean the watch glass or tubing before packing the capillary tubes which cause some impurities to be present. 2. To be higher than the correct melting point Heating the sample too quickly, the thermometer is not calibrated, or packing the sample too loosely in the capillary tubes. 3. To be broad in range (over several degrees) Using an impure sample, measuring a sample made up of large crystals, or using a large amount of sample size. 6. Compound A and compound B have approximately the same melting point. State two ways in which a mixed melting point of these two compounds would be different from the melting point of either pure A or pure B …show more content…
The mixed melting point will also be broader in range because of the impurities. Pure A and B would have a narrow range melting point compare to broader range of the mixed compound. 11. The melting points of pure benzoic acid and pure 2-naphthol are 122.5 °C and 123 °C, respectively. Given a pure sample that is known to be either pure benzoic or pure 2-naphthol, describe the procedure you might use to determine the identity of the sample. - Mix the unknown sample with pure benzoic acid. This is Mixture A. …show more content…
- Compare Mixture A’s melting point with the melting point of pure benzoic acid. If it is the same, then it is benzoic acid. If the mixture’s melting point is lower, this means it is not benzoic
Afterwards, we conducted crystallization to evaporate the liquid in an attempt to detect the presence of a salt. Before stating which of the potential
The cold pack experiment lab allowed us, the students, to apply theories learned in class to actual real life experiments; such experiments prepare us for future tasks the will be put forth to determine. Our main trajectory through this assignment was to determine what our unknown salt was, through experimental analysis. The main purpose of this lab was for us to determine what the given unknown salt is. For this experiment, my group and I were given unknown salt 7. Information recognized before starting the lab, were the materials needed, background information on the math required to determine the unknown(s). In addition, other background sources before starting the experiment included having previous knowledge of chemical formulas, understanding concepts learned throughout class and how a calorimetry works. Furthermore in order to determine how to complete the lab, we needed information upon how to properly keep the temperature of the water from decreasing or increasing, and this required that we needed to know what an insulator is and how to use ...
Categorize the following mixtures by telling if they are Heterogeneous (mechanical) or Homogeneous (solutions); fruit salad, lemonade, granola, chocolate chip cookies, bronze, saltwater, materials in a recycling pile, and sand water.
Aluminum foil was not used during the experiment to wrap around the Hickman still. The temperature of the hot plate continuously increased because the thermometer temperature increased very slowly. The stillhead started to collect condensate around 50°C which is much lower than the 80-90°C that the thermometer was supposed to read. A bent pipette was used to collect around 1.5mL of distillate that was put into a .5-dram vial. This vial was named “Fraction 1.” The hot plate temperature was increased a little more to increase the thermometer temperature in the Hickman still. .6mL of distillate was collected, using the same bent pipette, and put into another .5-dram vial named “Fraction 2.” The hot plate was turned off, and everything was left to cool for a little bit. After it cooled, around 1.2 mL of clear liquid was left in the original vial and transferred to another vial named “Fraction 3.” The syringe for gas chromatography was flushed with acetone and then with Fraction 1 before any reading was done. Because the syringe only collects .2µL of Fraction 1, the liquid wasn’t visible to the naked eye. The needle had to be twisted and rotated gently to insert into the injection port. When the LabQuest collected to data, there was one tall peak and a few little ones. The Percent Area for peak 1 was -197.78 and peak 2 was 297.78, and the Retention time for peak 1 was .700
For the first fraction, it was collected at temperatures between 79oC and 95oC. Based on the boiling point of Cyclohexane being 80.7oC and the boiling point of Toluene being 111oC, the first fraction should have been almost completely composed of Cyclohexane. The second fraction was collected at temperatures between 95oC and 100oC and should have been mostly composed of Toluene because the majority of the Cyclohexane should have been in the first fraction. Since the residual liquid was the liquid that had not boiled at a temperature of 100oC, then almost all of that remaining liquid should have been
The acids were smelled by wafting, and recorded in the data table. Five drops of the appropriate
measurements methods, and the temperatures of phase transitions. Fig. 1 is a typical phase diagram of
QUES. State whether the compounds above will be a gas or liquid state at room temperature (20 C). Hint: If the boiling point is below 20 C, then the liquid has already boiled andthe compound is a gas.
-Melting Point Trends: the amount of energy required to break a bond to change a substance from a solid to a liquid
Have you ever wondered why different elements have different melting and boiling points? Why some Molecules melt faster or take longer to boil? It all comes down to the forces and structure among the molecule. They are refer to as Chemical Bonding and Intermolecular or Intramolecular forces. The changes in states are due to changes in forces among the molecules rather than in those within the molecules (Zumdal 451). In this paper the effects of Chemical Bonding and Intramolecular Forces on the melting and boiling points of chemicals will be explained.
a homogeneous melt material, at a fixed and uniform rate, at a fixed head pressure, and a
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.
its state (Solid, liquid, gas); thus water has a higher melting point and a higher boiling
1. The labels have fallen off of three bottles thought to contain hydrochloric acid, or sodium chloride solution, or sodium hydroxide solution. Describe a simple experiment which would allow you to determine which bottle contains which solution.