FORMULA MASS 1 1.Determine the formula mass of the following compounds a.BeI2

b.Sr3N2

c.Fe2O3

d.PbI2

e.Sn(HSO4)2

f.Na2CO3

2.Determine the formula mass of the following compounds. a.silver bromide b.aluminum selenide c.stannic oxide d.cuprous sulfide e.aluminum hydroxide f.cupric nitrate

FORMULA MASS 2 1.Determine the formula mass of the following compounds. a.LiBr

b.CaO

c.FeF2

d.Cu2Se

e.BaSO4

f.Pb(CrO4)2

2.Determine the formula mass of the following compounds. a.silver phosphide b.magnesium bromide c.plumbous chloride d.tin (II) nitride e.zinc carbonate f.aluminum cyanide g.ferric oxide h.magnesium phosphate i.calcium carbonate

PERCENT COMPOSITION (with exact masses of substances) 1.A 14.80 gram sample contains 3.83 g of iron and 10.97 g of bromine. What is the percent composition of each element in this compound? 2.What is the percent composition of each element in an ore that contains 1.85 g of aluminum and 1.65 g of oxygen? 3.A compound contains 43.40 g of copper and 10.95 g of sulfur. What is the percent composition of each element in the compound? 4.A 13.61 g piece of calcium combines with 21.77 g of oxygen. What is the percent composition of each element in the compound? 5.Analysis of an unknown compound shows that it consists of 21.8 g of oxygen, 4.09 g of aluminum, and 6.36 g of nitrogen. What is the percent composition of each element in the compound?

6.An organic compound is found to contain 10.18 g of carbon, 1.47 g of hydrogen, and 0.93 g of oxygen. What is the percent composition of each element in the compound? 7.A certain sample of gas having a mass of 22.8 g contains 6.22 g of carbon and an unweighed quantity of oxygen. What is the percent composition of each element in the compound? 8.An organic compound consisting of carbon, hydrogen, and oxygen only weighs 13.669 g. Analysis shows that the compound contains 0.547 g of hydrogen and 8.707 g of oxygen. What is the percent composition of each element in the compound?

PENNY ACTIVITY

Directions: 1. Obtain a 1983 or later dated penny. Record the date in #1 below. 2. Use the steel file to make a nick on one edge of the penny. Make sure that the nick goes completely through the copper and makes it to the zinc(grayish colored). 3. Mass your penny. Record the mass in #2 below. 4. Place the penny in a small beaker (50mL) and ask the instructor to cover with 6 M HCl. Place in a secure area for several days with your beaker properly labeled and your group name on it. Questions/Calculations: 1.What was the date of your penny? 2.What mass the mass of your penny before the reaction? 3.What was the mass of your penny after reacting? 4.Which element did not react? 5.Which element did react? 6.What was the mass of the copper in the penny? 7.What was the mass of the zinc in the penny? 8.What were the percentages of copper and zinc in the penny? 9.List anything that may have caused your data to be lass than accurate.

PERCENT COMPOSITION 2

Determine the percent composition of each element in the following compounds. 1.rubidium chloride 2.barium phosphide 3.tin (IV) fluoride 4.cupric bromide

5.aluminum sulfite 6.ammonia 7. calcium phosphate 8. water 9. sodium carbonate 10. zinc selenide 11. ferrous chloride 12. calcium cholrate 13. cuprous oxide 14.magnesium nitride 15.lithium sulfide 16.ferrous oxide 17.lead (IV) chloride 18.tin (IV) nitrate 19.sucrose Review Formula Mass and % Comp 1. Find the formula mass of a. Aluminum Chlorate b. NaCl 2. Find the % composition of a. BaCl2 b. Strontium Nitite 3. Know the following: the law of definite composition, what hydrate means, what the water of hydrate is, and what anhydrous stands for. 4. Find % composition if 30.1 g of potassium reacts with 6.2 g of oxygen. 5. If a student has 400 grams of calcium chloride, how many grams of calcium atoms are present?

EMPIRICAL FORMULA

ASSIGNMENT 1

1.An oxide of arsenic contains 3.26 g of arsenic and 1.04 g of oxygen. What is the empirical formula for this oxide? 2.A sample of sodium oxide weighing 12.57 g contain 9.34 g of sodium. What is the empirical formula for this compound? 3.Analysis of a sample of a sulfur acid shows it to contain 0.17 g of hydrogn, 2.82 g of sulfur, and 5.67 g of oxygen. What is the simplest formula for this compound? 4.Analysis of a salt results in the following composition: 3.47 g of sodium; 2.12 g of nitrogen; and 7.27 g of oxygen. What is the empirical formula for this salt? 5.A barium salt is found to contain 21.93 g of barium, 5.12 g of sulfur, and 10.24 g of oxygen. What is the simplest formula of this compound?

EMPIRICAL FORMULA

ASSIGNMENT 2

From the percentage composition information following, calculate empirical formulas.

in

each

of

the

1.28.2% potassium, 25.6% chlorine, 46.2% oxygen 2.25.9% iron, 74.1% bromine 3.54.0% magnesium, 46.0 % phosphorus 4.46.3% lithium, 53.7% oxygen 5.68.4% chromium, 31.6% oxygen

MOLECULAR FORMULA ASSIGNMENT 1.A compound contains 88.2% carbon and 11.8% hydrogen. If the molecular mass is 68.0, what is the true molecular formula for the compound? 2.A compound contains 85.7% carbon and 14.3% hydrogen. If the molecular mass is 56.0, what is the true molecular formula for the compound? 3.A compound contains 80.0% carbon and 20.0% hydrogen. If the molecular mass is 30.0 what is the true molecular formula for the compound? 4.A compound contains 87.8% carbon and 12.2% hydrogen. If the molecular mass is 82.0, what is the true molecular formula for the compound?

CHEMISTRY LAB 15 QUANTITATIVE DETERMINATION OF AN EMPIRICAL FORMULA

NAME

PURPOSE:Prepare a tin and oxygen crystalline product and determine its formula PROCEDURE 1.Clean an evaporating dish and a watch glass cover. Dry as best as you can with a paper towel. 2.Determine the mass of the dish and cover.RECORD 3.Place about one grams of 20 mesh granulated tin into the evaporating dish. Cover the dish with the watch glass. Determine the mass of the dish, cover, and tin. RECORD 4.Take the dish, cover, and tin to a fume hood. 5.Remove the watch glass cover and add 2.5 mL of 8 M nitric acid to the dish.(Use the pipet to transfer the acid from the large container to the small container.) Immediately replace the watch glass cover. 6.After the chemical reaction has stopped, carefully take the dish to a hot water bath. Place the evaporating dish on top of the 150 mL beaker. 7.Heat on the water bath until the new mixture is milky white (about 5-10 minutes). Allow it to cool . Steam from the bath is HOT! 8.Remove the evaporating dish and place it on the wire gauze. Light the burner and heat with a moderate flame until the popping and spattering no longer occur. Turn the burner off, and allow the dish to cool, possibly 510 minutes. 9.When the dish has cooled, take the dish and cover to the balance to mass the dish cover, and new product. RECORD 10.Return the dish to the lab table to cool completely. 11.Clean up lab.

DATA TABLE: Mass of evaporating dish and cover (g) = Mass of dish, cover, and tin (g) = Mass of dish ,cover, and new product (g) = CALCULATIONS TABLE Mass of tin (g) = Mass of oxygen (g) = CALCULATIONS 1.Determine the moles of tin used in this experiment.

2.Determine the moles of oxygen that combined with the tin in this experiment.

3.Determine the empirical formula of the tin and oxygen product made in this experiment.

4.Name the solid product that was formed in this experiment.

CONCLUSIONS 1.What are the two possible ions which can be formed by tin? 2.Write the formulas for the compounds that can be formed by the two tin ions when they react with oxygen. 3.Does the empirical formula that you determined in this experiment agree with either one of the formulas written in Step 2? 4.List two possible sources of error in this experiment. FURTHER INVESTIGATIONS 1.Determine the percent composition of each element in the solid product you prepared in the experiment.

2.Analysis of a 20.30 sample of a compound containing phosphorus and oxygen shows that 8.87 g of the sample are phosphorus. Determine the empirical formula of the compound.

3.Upon analysis a compound is found to contain 7.75% hydrogen and 92.25% carbon by mass. Calculate the empirical formula for the compound.

4.By other experiments, the molecular mass of the compound in Problem 3 above is found to be 78. What is the molecular formula?