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Chapter 2 22. A student heats 0. 5585 g of iron with 0. 3550 g of sulfur. She reports that she obtains 0. 8792 g of iron sulfide and recovers 0. 0433 g of unreacted sulfur. Show by calculation whether or not her results obey the law of conservation of mass. Total mass initial = 0. 5585 g + 0. 3550 g = 0. 9135 g Total mass final = 0. 8792 g + 0. 0433 g = 0. 9225 g These two values should be equal by the law of conservation of mass. These results do not obey the law of conservation of mass. Possibly she made a mistake recording her numbers. 28. When 31 g of phosphorus reacts with oxygen, 71 g of an oxide of phosphorus is the product.
What mass of oxygen is needed to produce 13 g of this product? 31g + x = 71g 71g – 31g = 40g oxygen This means that in 71 g of the product there are 40 g of oxygen. 40/71 * 13 g = 7. 32 g 44. Gasoline can be approximated by the formula C8H18. An environmental advocate claims that burning 1 gallon (about 7 lb) of gasoline produces about 19 lb of carbon dioxide, a greenhouse gas. Explain this apparent contradiction of the law of conservation of mass. Because there is no oxygen added to the 7lbs of C8H18 and therefore, you cannot create oxygen without having oxygen because mass and matter is not created or destroyed. 6. Two experiments were performed in which sulfur was burned completely in pure oxygen gas, producing sulfur dioxide and leaving some unreacted oxygen. In the first experiment, 0. 312 g of sulfur produced 0. 623 g of sulfur dioxide. In the second experiment, 1. 305 g of sulfur was burned. What mass of sulfur dioxide was produced? 0. 312g S = 0. 623g So2 1. 305g S = x So2 0. 623g So2 *1. 30g S /0. 13g S =2. 61g So2 produced Chapter 3 6. What is the mass in u of each atom in Question 5? Atom A- 21 amu Atom B- 21 amu Atom C- 22 amu Atom D- 20 amu 7. Compare Dalton’s model of the atom with the nuclear model of the atom.
Dalton atomic model is the simplest model. Atoms only described as a very small ball but massive. This model is still not familiar with the charge within the atom. The nuclear model the atoms are not massive but hollow objects. Electrons are not scattered evenly in the nucleus but are at great distances from the nucleus. Rutherford’s theory also states that the electrons are not silent but orbit around the nucleus. 9. What are the symbol, name, and atomic mass of the element that has 18 protons in the nucleus of its atoms? Symbol= Ar (Argon) mass= 39. 948g 10. Explain what is meant by the term atomic mass.
Atomic mass is the weight of protons and neutrons combined in an element 14. How many electrons are there in the neutral atoms of the elements listed in Question 13? Helium= 2Oxygen= 8 Sodium=11Magnesium= 12 Chlorine=17Sulfur= 16 16. Fill in the following table: Element Mass Number Protons Neutrons – Cobalt602732 – Fluorine 19 910 – Uranium23892143 – Lead20782124 20. Without referring to the periodic table, give the atomic numbers of the elements with the following electron structures. a. 1s2 2s2 2p6 3s2 3p1 = 13 . 1s2 2s2 2p6 3s1 = 11 c. 1s2 2s2 2p6 3s2 3p6 4s2 = 20 Chapter 4 2. What are the structural differences among chlorine atoms, chlorine molecules, and chloride ions? How do their properties differ? A chlorine molecule consists of two chlorine atoms bound together by a covalent bond. The symbol of a chlorine molecule is Cl2. Chlorine atom is the chemical element with atomic number 17 and symbol Cl. Chloride is either an ion (with extra electron), or a covalent or ionically bounded substance Chlorine atom – 2,8,7(unstable,reactive) Chloride ion-2,8,8(stable,not very reactive) 3.
Indicate charges on simple ions formed from the following elements. a. group 3A = +3 b. group 6A = -2 c. group 1A = +1 d. group 7A = -1 5. How many covalent bonds do each of the following usually form? You may refer to the periodic table. a. H = 1 b. C = 4 c. O = 2 d. F = 1 e. N = 3 f. Br = 1 8. Give Lewis symbols for each of the following elements. You may use the periodic table. a. nitrogen = N b. chlorine = Cl c. boron = B 10. Give Lewis structures for each of the following. a. magnesium oxide = MgO b. strontium chloride = SrCl2 c. sodium bromide = NaBr d. lithium nitride = Li3N 14. Refer to page 97.
Then use that information to name the following ions. a. Mo4+ = molybdenum(4+) b. Mo6+ = molybdenum ion 18. Name the following binary ionic compounds. a. LiF = lithium fluoride b. CaCl2 = calcium chloride c. MgS = magnesium sulfide d. AgI = Silver iodide e. CuO = copper (II) oxide f. Cu2O = copper (I) oxide 22. Give formulas for the following. a. silver nitrate = AgNO3 b. lithium chromate = Li2CrO4 c. magnesium nitrite = Mg(NO2)2 d. copper(I) phosphate = Cu3(PO4)2 24. Name the following. a. KMnO4 = Potassium permanganate b. CaCO3 = Calcium carbonate c. Li2C2O4 = Lithium Oxalate d. Cu(OH)2 = Copper(II) hydroxide 2. Give formulas for the following covalent compounds. a. oxygen difluoride = OF2 b. chlorine trifluoride = ClF3 c. tricarbon dioxide = C3O2 34. Name the following covalent compounds. a. CBr4 = Tetrabromomethane b. Cl2O7 = Dichlorine heptoxide c. P4S10 = Phosphorus pentasulfide 36. Give Lewis formulas that follow the octet rule for the following covalent molecules. a. NCl3 b. C2H4 c. H2SO4 d. C2H2 e. CH2O f. SCl2 38. Give Lewis formulas that follow the octet rule for the following ions. a. CN? b. ClO2? c. HSO4? 40. Classify the following covalent bonds as polar or nonpolar. a. H — N = polar b.
Be — F = ionic c. P — Cl = polar 46. Classify the bonds in the following as ionic or covalent. For bonds that are covalent, indicate whether they are polar or nonpolar. a. NO = polar b. CaO = ionic c. NaBr = ionic 56. Which of the following atoms or molecules are free radicals? a. S = not a free radical b. NO2 = free radical c. N2O4 = not a free radical 66. Is there such a thing as a sodium chloride molecule? Explain. Sodium chloride is a compound that consists of ions. There is no such thing as a molecule of sodium chloride. Instead, sodium chloride consists of sodium ions and chloride ions.