Experiment 2: Intermolecular Forces
Performed: 9/12/2011
Submitted: 9/20/2011
Chemistry 1046L
PART I:
Purpose:
The purpose of partI in this experiment is to identify a variety of unknown substances’ properties using observations of the temperature changes that occur during evaporation. We know that substances with weaker intermolecular forces, such as London dispersion, will have a faster vaporization rate and thus a higher temperature difference compared to those with stronger molecular bonds such as hydrogen and dipole-dipole forces. By measuring the average kinetic energy (or the temperature) of the liquid left behind after some evaporation takes place, we can determine its type of intermolecular
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Also, to familiarize students with Boyle’s law to determine the pressure neededin order to determine the unknown triplet point as well as calculating percent error to accurately publish our experimental data.
Data:
Observations:
Dry ice was white, cylindrical shaped solid that smoked and sublimed when placed onto paper towel. The solids were crushed into a fine grain and a few small chunks. While in the pipet, the dry ice crystallized on outside bottom and inside some layer of “fog” and smoke was created. During submersion into the cup of water, the dry ice observed began to liquefy (the triple point) and after the first slight release of the pliers on the pipet, there was an explosion.
Calculations:
P1 V1 = P2 V2
Pressure of the room taken off the barometer: 10125 kPa
1015 kPa X 1 atm = 10.02 atm 101. 325 kPa
(10.02 atm)(5 mL) X (P2 )(3 mL)
P = 16.7 atm
% Error = 16.7 – 5.1X 100 = 233% 5.1
Conclusion: Based on the observations, it is concluded that unknown C is water because this substance has the least decrease in temperature which correlates to high intermolecular forces. Out of the five unknowns, water has the strongest intermolecular forces having hydrogen bonding. The substance with the weakest
All standardizations are performed in triplicate. Weigh out .1000-.1200 gram KIO3. Add 70-80 mL of deionized water. Swirl and dissolve. Add 3 mL of 6M HCl. Swirl and mix. Quickly titrated the brow-red solution with 0.1M Na2S2O3 until it is light yellow. Then add 3.5 mL of starch indicator. Titrate again until the dark color first disappears.
pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.
1. Move the lid of the container up or down. Record the resulting volume and pressure
The unknown liquid was also conductive and had a higher boiling point. Considering these results, we concluded that the unknown liquid was not pure water. In lab 3, we designed experiments to determine how many substances the unknown liquid contained. We first observed the unknown liquid
Think about the gas laws we are studying. Boyle’s law tells us that pressure and volume are inversely proportional. Charles’ law states that volume and temperature are directly proportional. We also know that pressure and temperature are directly proportional. Discuss at least one instance in your personal experience where you have seen one or more of these laws in action.
6. Select the lab book and click on the data link for Ideal Gas 1. In the Data Viewer window, select all the data by clicking on the Select All button and copy the data using CTRL-C for Windows or CMD-C for Macintosh. Paste the data into a spreadsheet program and create a graph with volume on the x-axis and pressure on the
A buffer is a solution that resists changes in pH when H+, OH-, or H20 is added. By using standard lab equipment, a lab pro diagnostic tool, and acidic and basic solutions, the pH can be found. By recording the pH while adding a base or an acid gradually to a buffer solution you can find the capacity of each buffer to resist drastic changes in pH. The best buffers will keep a solution from becoming either too acidic or basic with the addition of a strong base or acid.
2A. Evaporation is related to the properties of matter because it is a liquid and a gas. We know this because there are three states of matter which are soild, liquid and gas since evaporation first starts as a liquid (water). Then it turns into gas (cloud).
b. Place crushed ice in the beaker so the water level is just below the top of the
For this lab, we brought a empty soda can to school to show how pressure and temperature can affect the structure of the can. To begin the experiment, we needed a empty soda can, water and ice in a small plastic tub, and a hot plate. First, we added about a tablespoon of water to the empty soda can. Second, we put the soda can on the hot plate and waited until the water was brought to a boil. Then we used beaker tongs to carry the hot soda can and flipped it over into the container of water and ice. Once the can touched the water, the can made a loud crushing sound and the can crippled inward.
1. Start Virtual ChemLab and select Boyle’s Law: Pressure and Volume from the list of assignments. The lab will open in the Gases laboratory.
In this experiment, the identity of an unknown compound will be deduced from analysis of physical properties, boiling points, IR spectra, chemical tests, and melting points of derivatives. This experiment allows for individual selection of chemical tests, order of steps, and additional analysis, as necessary, based on what is needed to determine identity of unknown.
B. How does this graph illustrate Boyle’s law? As more pressure is added the volume decreases and the graph shows this because it is decreasing as well. _________________________________
The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. Through the experimentation of three substances, tetracosane, 1-tetradecanol and a mixture of the two, observations can be made in reference to melting point concerning polarity, molecular weight and purity of the substance. When comparing the two substances, it is evident that heavy molecule weight of tetracosane allowed
The volume is definite if the temperature and pressure are constant. When a solid is heated above its melting point, it becomes liquid, given that the pressure is higher than the triple point of the substance. Intermolecular (or interatomic or interionic) forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the most well known exception being water, H2O. The highest temperature at which a given liquid can exist is its critical temperature.[5]