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 be lower than the melting points of pure A or Pure B.
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…
- Taking the melting point of Mixture A using the capillary tube melting-point method.
- 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
acid. - If it is not benzoic acid, proceed to mix the unknown sample with pure 2-naphthol. This is Mixture B. -Take the melting point of Mixture B. - Compare Mixture B’s melting point with the melting point of pure 2-naphthol. If the melting points are the same, then the unknown sample is 2-naphthol. 13. The melting point-composition diagram for two substances, Q and R, is provided in Figure 3.2 (page 121), which should be used to answer the following questions. 1. What are the melting points of pure Q and pure R? Q= 180°C R=155°C 2. What are the melting point and the composition of the eutectic mixture? Melting point is 80°C and the compositions are 65% mol Q and 35% mol R 3. Would a mixture of 20 mol % Q and 80 mol % R melt if heated to 120 °C? to 160 °C? to 75 °C? No, the mixture would not melt at 120°C, yes to 160°C, no to 75°C.
It was learned that changing the volume of the same substance will never change the boiling point of the substance. However having two different substances with the same volume will result in two different boiling points. The purpose of this lab was to determine if changing the volume of a substance will change the boiling point. This is useful to know in real life because if someone wanted to boil water to make pasta and did not know how much water to
Possible sources of error in this experiment include the inaccuracy of measurements, as correct measurements are vital for the experiment.
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 ...
One possible source of experimental error could be not having a solid measurement of magnesium hydroxide nor citric acid. This is because we were told to measure out between 5.6g-5.8g for magnesium hydroxide and 14g-21g for citric acid. If accuracy measures how closely a measured value is to the accepted value and or true value, then accuracy may not have been an aspect that was achieved in this lab. Therefore, not having a solid precise measurement and accurate measurement was another source of experimental error.
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.
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
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.
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.
a homogeneous melt material, at a fixed and uniform rate, at a fixed head pressure, and a
The acids were smelled by wafting, and recorded in the data table. Five drops of the appropriate
-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.
its state (Solid, liquid, gas); thus water has a higher melting point and a higher boiling
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.