CHEM110L CSUN Determination of Empirical Formula Lab Report

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Nyzbevl

Science

CHEM110L

California state university Northridge

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please read the attachments before writing the report.

Read the intro 1,2 &3 that we followed for lab experiment to know the tools we used and the chemicals and the steps.

Report sheet are attached which include all the data that we collected for this lab report is attached from my note book. (use the data in the note sheet)

Report Style:

1-Cover Page (50 points)

2-Introduction (50 points) (should include what is the lab about, how the report will cover the experiment. General information about the topic) full page

3- Typed data and observations (400 points) (should include all the data attached as report sheet with further information like what you think of the reaction and how we got these numbers. Also, pictures while doing the experiment will be attached,)

4-Conclusion (500points) (explanation of the experiment and what you learn from this experiment and what you think) (explosions of how you thing the data are, and explain what error occurred in the experiment)

(There will be more pictures to attached during the experiment)

(There will be a plagiarism check)

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Mass of magnesium Mass of Mg= 40.195 g Number of moles of magnesium Number of moles of oxygen

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13 SMART . . Calculations Mass of magnesium Mass of Mg = 40.195 g - 40.000 g = 0.195 g Number of moles of magnesium Mol Mg = 0.195 g/(24.305 g/mol) = 8.02 X 10-3 mol Mass of Mgox = 35.322 g - 35.000 g = 0.322 g Number of moles of oxygen Mass of oxygen = mass of Mgo, - mass of Mg = 0.322 g -0.195 g = 0.127 g Mol O = 0.127 g/(15.9994 g/mol) = 7.94 X 10-3 mol • For Mg: 8.02 X 10-3 mol/8.02 X 10-3 mol = 1.00 For O: 8.02 X 10-3 mol/7.94 X 10-3 mol = 0.990 Empirical formula is Mgo . . . . . Smallest integral ratio of Divide by smaller moles numbe: Element Number of moles Magnesium Oxygen Empirical (simplest) formula for magnesium oxide SMART Sample calculations for three significant figures • Mass of Mg = 0.195 g • Mass of Mgox = 0.322 g • Mass of oxygen = mass of Mgox - mass of Mg = 0.322 g - 0.195 g = 0.127 g • Mol Mg = 0.195 g/(24.305 g/mol) = 8.02 X 10-3 mol • Mol O = 0.127 g/(15.9994 g/mol) = 7.94 X 10-3 mol For Mg: 8.02 X 10-3 mol/8.02 X 10-3 mol = 1.00 . For O: 8.02 X 10-3 mol/7.94 X 10-3 mol = 0.990 • Empirical formula is Mgo SMART EXPERIMENT #4: DETERMINATION OF EMPIRICAL FORMULAS What is an Empirical Formula and how do we use it? Benzene H H H Acetylene H H H H-CC-H Co Ho C2 H₂ CH Special Apparatus and Chemicals: Crucible and Lid Bunsen burner Clay Triangle Dropper Wire Gauze Crucible tongs Iron ring and stand ~0.3 g Mg metal Report: Cover Sheet (50 points) Brief Introduction (50 points) Typed Data (500 points) Brief Conclusion (100 points) Calculations (100 points) 2 Mass of empty crierble and lid 22.03g g mass of crucible, lid, and mag resium 22.30g g After added leader heutes 22.939 Mass of Magnesium 230. (0.773/24,30 und) -9 Number of moles of Magonesicum (show Code) 0-012.ml Mass of crucible, lid, Majanisum Oxide 22.934 9 mass of Crucible, lid, Maganisum 22.809 g mass at Oxygen 0.17 g g Number of roles of oxygen Deely. mol Calculatims: 0.17 g/lis.9499/mah) = gma - 3 Ou Signature Date Witness/TA Date THE HAYDEN-MCNEIL STUDENT LAB NOTEBOOK Note: Insert Divider Under Copy Sheet Before Writing 2:39 PM Tue 8 Oct 12% Done : intro1 2 (1 of 86) EXPERIMENT #4: DETERMINATION OF EMPIRICAL FORMULAS Purpose: The purpose of this experiment is to determine the empirical formula for magnesium oxide after burning magnesium in air. Special Apparatus and Chemicals: Crucible and Lid Bunsen burner Clay Triangle Wire Gauze Dropper Crucible tongs ~0.3 g Mg metal Iron ring and stand Discussion: Chemistry as a science did not begin until people started to wonder about the internal structure and composition of matter. Before people could begin to ask questions about the structure and composition of matter they first had to realize: 1. Each element is composed of small particles called atoms. 2. All atoms of a given element are chemically identical; atoms of different elements have different properties. 3. Atoms are neither created, destroyed, nor transmuted in chemical reactions. (Law of Conservation of Mass) 4. Compounds are formed when atoms of two or more elements combine; the relative number and kind of atoms are constant for a given compound. (Law of Constant Composition) These principles formed the basis of Dalton*s Atomic Theory and are the fundamental principles of modem chemical science. Dalton extended these principles to develop the Law of Multiple Proportions: If two elements combine to form more than one compound, the ratio of the masses of the elements in the two compounds may be represented by as small whole numbers. When the chemical formula for a compound is written as the smallest whole number ratio of atoms in a compound we call that the empirical ("experimentally determined") formula. In practice, the composition of a compound is often first determined experimentally as a mass percentage or ratio. The mass percentage can then be converted to the smallest whole number ratio of the atoms if the atomic weights of the elements are known. If the compound is molecular rather than ionic, further experiments could determine the molecular 2:39 PM Tue 8 Oct 12% Done : intro1 2 (1 of 86) EXPERIMENT #4: DETERMINATION OF EMPIRICAL FORMULAS Purpose: The purpose of this experiment is to determine the empirical formula for magnesium oxide after burning magnesium in air. Special Apparatus and Chemicals: Crucible and Lid Bunsen burner Clay Triangle Wire Gauze Dropper Crucible tongs ~0.3 g Mg metal Iron ring and stand Discussion: Chemistry as a science did not begin until people started to wonder about the internal structure and composition of matter. Before people could begin to ask questions about the structure and composition of matter they first had to realize: 1. Each element is composed of small particles called atoms. 2. All atoms of a given element are chemically identical; atoms of different elements have different properties. 3. Atoms are neither created, destroyed, nor transmuted in chemical reactions. (Law of Conservation of Mass) 4. Compounds are formed when atoms of two or more elements combine; the relative number and kind of atoms are constant for a given compound. (Law of Constant Composition) These principles formed the basis of Dalton*s Atomic Theory and are the fundamental principles of modem chemical science. Dalton extended these principles to develop the Law of Multiple Proportions: If two elements combine to form more than one compound, the ratio of the masses of the elements in the two compounds may be represented by as small whole numbers. When the chemical formula for a compound is written as the smallest whole number ratio of atoms in a compound we call that the empirical ("experimentally determined") formula. In practice, the composition of a compound is often first determined experimentally as a mass percentage or ratio. The mass percentage can then be converted to the smallest whole number ratio of the atoms if the atomic weights of the elements are known. If the compound is molecular rather than ionic, further experiments could determine the molecular 2:39 PM Tue 8 Oct 12% Done intro3 (2 of 86) CONCEPT: After a known amount of magnesium metal is burned in the air, the product will be mostly magnesium oxide with some magnesium nitride (Mg3N2). You will add water to convert the magnesium nitride to magnesium hydroxide which upon further heating will lose water to give magnesium oxide. The amount of oxygen that has combined with the magnesium can be determined by the difference in weight before and after heating. Once the number of moles of magnesium and oxygen are known, the empirical formula is the smallest whole number ratio of these amounts. PROCEDURE: Obtain a crucible and crucible lid. Wash the crucible and lid to remove any loose material from previous reactions and then dry the crucible and lid over a Bunsen burner with a cool flame for a few minutes. Let the crucible and lid cool to room temperature and then weigh the crucible and the lid together. Next add approximately 0.3 grams of magnesium metal to the crucible and weigh the crucible, lid, and magnesium together. Be sure to record all weights to the full precision of your balance. Cover the crucible and heat over a low flame for 2 or 3 minutes. CAUTION: The crucible is ceramic and may crack or break when heated strongly. Also, a hot crucible is visually indistinguishable from a cool crucible, be careful not to burn your hands. Increase the air flow to produce a hot flame and heat the crucible while the bottom is glowing red hot for 10 minutes. CAUTION: Magnesium may ignite if heated open to the air at this point. After the 5 minutes carefully lift the cover to see if the magnesium has begun to react. CAUTION: If you notice a bright white glow or white smoke beginning to form, close the lid immediately adjust the flame and heat the magnesium a couple of more minutes before carefully checking the reaction again. If no glow or smoke forms, tip the cover so it is slightly open and heat the crucible while red hot for 5 more minutes. After heating for 5 more minutes with the cover tipped you should see a gray-white powder in the crucible. Remove the flame and let the crucible cool slightly (2 or 3 minutes). Then carefully add 5 drops of distilled water to convert any magnesium nitride that might have formed during the initial heating to magnesium hydroxide. You may notice a slight odor of ammonia at this point. Heat the crucible over a low flame for 2 or 3 minutes. Then adjust the flame and heat the crucible with the bottom glowing red hot for 10 minutes. After heating, shut off the Bunsen burner and allow the crucible and lid to cool to room temperature before weighing again. After weighing heat again for 5 minutes, cool and weigh again; heat until a constant weight is obtained. DISPOSAL: Mgo should be disposed of in the trash can. Remember to wash out your crucible and lid. The difference in the initial weight of magnesium and the weight of the magnesium oxide that formed is of course the weight of the oxygen that combined with the magnesium. Calculate the empirical formula for the magnesium oxide formed. 2:39 PM Tue 8 Oct 12% Done : intro2 (3 of 86) weight of the compound. Knowing the empirical formula and the molecular weight, one can determine the molecular formula of a compound. The molecular formula of a compound indicates the actual numbers and types of atoms in a molecule rather than just the ratio. In this experiment you will experimentally determine the composition of magnesium oxide made by burning magnesium metal in the presence of air. Magnesium will combine with molecular oxygen (O2) from the air to form magnesium oxide. magnesium + oxygen = magnesium oxide You have probably seen this reaction before sparklers are made of magnesium metal. Also, road flares are made of magnesium with strontium added to give a red color. In this experiment you will control the rate of the reaction to prevent igniting the magnesium by limiting how fast air can get to the magnesium. [At this point with a little thought, you could determine the formula of magnesium oxide because you know (you should know) what ionic charges magnesium and oxygen like to take, and therefore, you know in what ratio they would combine together. However, you are going to confirm this experimentally.] As you know, air is a mixture composed mainly of molecular nitrogen (N2) and oxygen (O2) consisting of about 80% nitrogen and 20% oxygen. It turns out that magnesium will react with both nitrogen and oxygen under the conditions of the experiment. When you initially heat the magnesium metal, you will form not only magnesium oxide but also some magnesium nitride (Mg3N2) as well. Fortunately, by adding water to magnesium nitride you can convert magnesium nitride to magnesium hydroxide and ammonia. Upon further heating, the magnesium hydroxide will be converted to magnesium oxide by loss of water. Knowing the mass of magnesium metal that you started with and determining the mass of oxygen that combined with the magnesium, you can calculate the empirical formula which is the smallest whole number ratio of moles of magnesium to oxygen. The following is an example of how to calculate an empirical formula given typical experimental data: A student burns 0.510 grams of elemental phosphorous and finds that 1.155 grams of phosphorous oxide are produced. What is the empirical formula for this oxide? 0.510g P x (1 mole P)/(30.97 g P) = 0.01647 moles P 0.645g 0 x (1 mole O)/(16.00 g O) = 0.04031 moles O (0.01647 moles P)/(0.01647 moles P) = 1.00 moles P/mole P (0.0405 moles O)/(0.01647 moles P) = 2.46 mole O/mole P The ratio of P to O is very close to 1 to 2.5. To convert this ratio to small integer numbers, multiply by 2. Certainly, within experimental error we can be confident in assigning this phosphorous oxide an empirical formula P205. B
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CHEM 110L-002
General Engineering Chemistry I
Fall, 2019

(DETERMINATION OF EMPIRICAL FORMULA FOR MAGNESIUM OXIDE)

Date: 10/9/2019

Introduction
According to Dalton’s Law of Multiple Proportions, elements combine in specific whole numbered ratios to
form specific compounds. Chemical formulas can be written as a smallest whole number ratio of combined
atoms. When written in this form, the chemical formula is known as an Empirical Formula. Empirical means
“experimentally determined” in this case. Empirical formula is often different from the molecular formula.
Empirical formula is the simplest whole number ratio of elements that combine to form a compound, while
molecular formula represents the specific proportions present in a compound. For example, the Empirical
formula for benzene is CH, while the molecular formula is C6H6. (www.socratic.org, n.d.) More than one
molecular formula can exist for the same Empirical Formula. Both benzene (molecular formula C6H6 ) and
acetylene (molecular formula C2H2) have the empirical formula CH. Any unknown sample which shows an
elemental analysis with Empirical Formula CH could possibly be acetylene, benzene, or any other molecule that
contains only C and H and contains them in a 1:1 ratio. (Chemcollective.org, n.d.)

The purpose of this experiment was to experimentally determine the Empirical Formula for an oxide of
magnesium (MgOx). Magnesium metal burned in air combines with the oxygen in the air with a primary
product of magnesium oxide.
2 Mg (s) + 1 O2 (g) → 2 MgO (s)

A side product is also produced by combination of magnesium and nitrogen in the air. This side product is
magnesium nitride.
3 Mg (s) + 1 N2 (g) → 1 Mg3N2 (s)

2

Addition of drops of distilled water converts the magnesium nitride to magnesium hydroxide. Magnesium
hydroxide is converted by further heating to magnesium oxide by loss of water.
1 Mg(OH)2 (s) → 1 MgO (s) + 1 H2O

The mass of magnesium is subtracted from the final weight of magnesium oxide after heating to yield the
mass of oxygen consumed. By using the molecular weights of magnesium and oxygen, moles of magnesium
and moles of oxygen are calculated. The ratio of these moles is the experimentally-determined ratio of
magnesium to oxygen in the product, MgOx.. This ratio, rounded off and expressed as whole numbers, provides
the experimentally-determined Empirical formula for magnesium oxide, MgOx.

In this lab report, the purpose, background, and chemical reactions have been covered in the Introduction.

The materials used in the experiment are covered in the Materials section. The stepwise procedure is covered in
great detail in the Procedure Section. In the Data and Observations sections, photos of the actual experiment in
progress are presented with descriptions. A photo of the Raw Data recorded in the Student Laboratory
Notebook is provided. These Raw Data are then used in the Calculations section to show how mass of
magnesium, mass of magnesium oxide, and mass of oxygen are calculated. By use of atomic weights, detailed
calculations are shown for determining moles of Mg and O. Calculation of a mole ratio for Mg : O is then
shown and explanation is ma...

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