Introduction:
To properly complete this lab, a basic understanding of mass, moles, and empirical formula is required. Mass is a unit of measurement that is used to determine the number of grams in a certain object. A mole is a measurement in which the amount of substance that is present can be determined.To convert between from mass to moles the amount of grams present is divided by the atomic mass to find moles. To get back to mass from mols the amount of mols is multiplied by the atomic mass. An empirical formula is a chemical equation with the simpliest positive ratio possible. To find an empirical formula the elements in the formula must be in moles. Then the smallest amount of moles is used to divide all the other mole numbers. These numbers
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are then rounded to the nearest whole number and are used as the subscript for their corresponding element.
The purpose of this lab is to use lab equipment and procedure to gather data about the mass of an undefined amount of magnesium and oxygen. This data is then meant to be used to find the empirical formula of a magnesium oxygen compound.
Materials/Equipment:
Crucible with cover
Ring stand
Magnesium Ribbon
Iron ring
Clay triangle
Crucible tongs
Dropper pipet
Scissors
Burner
Balance
scale
Safety goggles
Lab apron
Procedure:
To start the lab, all participants should put on all proper safety equipment, tie up hair, and roll up sleeves. Then they should get a crucible with a cover and place that on a clay triangle. A ring stand and iron ring should then be set up and a bunsen burner should be lit and adjusted to a proper flame. The crucible with cover and the clay triangle should be placed on the iron ring and in the hottest part of the bunsen burner’s flame for three minutes. After three minutes, the crucible and cover should be removed from the flame and allowed to cool. Once cooled, a scale should be used to calculate the mass of the empty crucible with the cover. Then a 20 centimeter piece of magnesium ribbon should be cut into one centimeter pieces and placed in the crucible. The mass of the crucible should be
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measured again now that it has magnesium in it. The crucible should then be covered and heated lightly for two minutes. After two minutes the cover should be tilted off the crucible to allow for air to move in and out of the crucible. The crucible should be moved into the strongest part of the flames and should stay there for ten minutes. After ten minutes, the burner should be shut off and the crucible should be cooled until it can be touched. The contents of the crucible should be examined and if any unreacted magnesium is still in the crucible, the crucible should be reheated. Once cooled, a dropper pipet should be used to add a small amount of water so that only the reacted magnesium is covered. The crucible should then be placed back on the clay triangle without a cover and is to be heated gently as to not spatter the water. If a vapor is noticed from the crucible, it is to be wafted to see if there is an odor. Once all the liquids have been boiled off, more water is to be added and the crucible should be heated gently again. Once all the water has been boiled off again, the crucible is to be strongly heated for five minutes. After five minutes, the burner should be shut off and the crucible should be cooled. Once cool, the mass of the crucible is to be taken one last time. After the group has all its data, all materials are to be cleaned and returned to their rightful place. Data: Mass (Grams) Object Mass Empty Crucible 26.48 grams Crucible and Magnesium 26.58 grams Crucible and Oxide 26.65 grams Data Analysis: Mass of Magnesium used (mass of crucible+Mg)-(mass of empty crucible)=26.58-26.48=0.1 grams of Magnesium Mass of oxygen that reacted (mass of crucible+oxide)-(mass of crucible+Mg)=26.65-26.58=0.07 grams of Oxygen Number of g-atoms of Magnesium used (mass of Mg)/(atomic mass of Mg)=0.1/24.305=0.0041 Number of g-atoms of Oxygen reacted (mass of O)/(atomic mass of O)=0.07/15.999=0.004 Ratio of g-atoms of Magnesium to g-atoms of Oxygen (g-atoms of Mg):(g-atoms of O)=0.0041:0.004=1:1 Percent error 100*(experimental-theoreticaltheoretical)=100*(0.004-0.00410.0041)=2.4% error Conclusion: The conclusion that could be drawn from this is that the empirical formula of a Magnesium and oxygen compound would be MgO with a 1:1 ratio.
The ratio is one to one because there was .004 moles of oxygen reacted in the crucible and .0041 moles of Magnesium. The ratio of these two numbers when it is rounded to the nearest whole number is 1:1. Some potential errors that could have happened in the lab process that could cause varying data among lab participants include; the strength of flame, size of magnesium ribbon, and the amount of water added. During the lab, a bunsen burner is required to evaporate water from the crucible and start other reactions. If the flames are at different strengths then different amounts of water could have been evaporated from each dish, causing a change in mass. Also, specific to our lab, the magnesium ribbon was only broken by hand and not broken into precise 1 centimeter pieces like asked in the lab. This caused the ribbons to vary in length which could sque the data. Another error was that there was no set amount of water that was to be added. This means that the amount of water added could vary per group and so could the amount of oxide found in the dish after heating. Some changes that could be made to improve the lab would be to specify a specific amount of water that should be added to the crucible each time it requires water. Also, if a larger amount of magnesium was used in a future experiment it would be easier to determine the moles
and molar ratio.
to get an idea of how I would do my real experiment and what apparatus
The procedure of the lab on day one was to get a ring stand and clamp, then put the substance in the test tube. Then put the test tube in the clamp and then get a Bunsen burner. After that put the Bunsen burner underneath the test tube to heat it. The procedure of the lab for day two was almost exactly the same, except the substances that were used were different. The
DH=-285.5 kJ/mol. In this investigation, we will be working with potentially dangerous chemicals and safety precautions must be made. Magnesium oxide is a respiratory and eye irritant, the dust must not be inhaled and all work with MgO should be conducted in the fume hood ( Cartwright, 2002). Hydrochloric acid is extremely corrosive, inhalation of the vapor can cause serious injury, ingestion could be fatal, and the liquid can cause severe damage to the skin and eyes; when working with HCl splash goggles and gloves should be worn, and work should be conducted in a well ventilated area (Cartwright, 2002). Materials and Methods --------------------- Goggles - Lab apron - Magnesium oxide MgO - 1g. Lab balance 100mL graduated cylinder Hydrochloric acid HCl - 200mL/.5M. - 2 plastic foam cups - thermometer - cover for cup - Magnesium (Mg) ribbon - 600mL beaker (base for calorimeter) - 400mL beaker (transportation of acid).
The purpose of this lab was to calculate the percent composition by mass of oxygen in potassium chlorate.
The mass of Mg + the mass of O2=mass of MgxOx. Knowing the mass of
6. Heat the crucible and its content with the lid off until the magnesium begins to glow
Get together a clay triangle, ringstand, and a burner. Wash a crucible. Locate the crucible onto the ringstand. Warm the crucible on the scorching section of the flame from the burner for approximately five minutes. Chill the crucible at room temperature. Then, weigh it precisely. Grasp the crucible using tong because the use of hands will add oils and residues on to crucible. Place roughly 2 grams of copper sulfate inside the crucible. Then, measure the weight of the crucible along with its contents. Position the crucible onto the clay triangle. Next, heat up the crucible steadily at the beginning to avoid splattering. Once heated to the shade of red, place on the hot part of the bunsen burner flame for precisely five minutes, chill to room temperature, and find the mass of the crucible including its contents. Document the weight on the data sheet. Put the crucible on the ringstand. Pour a small about of distilled water into the crucible. Wait about five minutes to see reaction that is made. Find the mass of the crucible. Indicate the mass on data sheet.
4. Pour about 300mL of tap water into the beaker. Set up a hot-water bath using a hot plate, retort stand, and thermometer clamp. Alternatively, use a Bunsen burner, retort stand, ring clamp, thermometer clamp, and wire gauze.
We’d note down the weight. Then we’d get our solutions ready. We were only given a 100% solution and a 0% solution, so we had to mix them in the right ratio to get all the solutions we needed. We decided to do 5 different types of solutions so we would have a wide range of results and it would be more accurate. We’d use 100%, 75%, 50%, 25%, 0% solutions in our experiment.
Placed a 400 mL beaker that is 2/3 full of water on a hot plate in the fume hood and brought the water to a boil. While the water was boiling, weighed and empty weighing boat then took the solid metal sample and weighed it in the weighing boat. Recorded the two weighs and subtracted the values to calculate the mass of the metal.
4. Fill the graduate cylinder to the 30.0mL mark with tap water. Remember to read the bottom of the meniscus. This is the initial volume, V initial. Record the mass of the graduate in the row labeled graduate+water+0 pebbles. Repeat this step with 10, 20, and 30 pebbles.
Quickly and carefully transfer the heated metal from the test tube to the water in the calorimeter.
•density of the chemical elements displayed on a miniature periodic tableDensity of solid: 2030 kg m-3...
3 cm of magnesium ribbon generally has a mass of 0.04 g and yields 40 cm3 of hydrogen when reacted with excess acid. 50 cm3 of 1M hydrochloric in this experiment is in excess.
Whilst doing the experiment there are many things that will have to remain the same in order to keep the tests fair, these include amounts and measurements as well as concentration and size and shape of the magnesium e.g. long strands. The temperature how ever will be the main change in the experiment, this is the only factor to change in less problems occur where a change is not optional. For each temperature the test will be taken three times to make sure that the results are correct and as accurate as possible, an average will be taken to give a clear and single result. A diagram of the apparatus I intend on using and how it will be assembled; [IMAGE] Safety- To ensure that the investigation is safe I will make sure that all equipment it correctly assembled, and I am wearing the appropriate safety wear and that everybody around is either dressed correctly or far enough away.