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ELEMENTS OF CHEMISTRY I EXAM II October 23, 2000 INSTRUCTIONS: PRINT YOUR NAME ————> NAME WORK # 1 WORK 5 OF #2 THROUGH #8 SHOW YOUR WORK FOR PARTIAL CREDIT THE LAST PAGES ARE A PERIODIC TABLE AND A SCRATCH SHEET R = 0.08206 lit-atm/mol-K 1 R = 8.3145 J/mol h = 6.626 X 10-34 J-s c = 2.9979 X 108 m/s ∆Hvaporization for H2O at 100 °C = 40,700 J/mole 2 3 4 5 6 7 8 TOTAL(150) 1. .Define the terms or give a short answer for each of the following (a) Characterize the following bonds as nonpolar, polar, or ionic. The table at the bottom of the page might be helpful. C - F ______________ Mg - O _______________ F- F _______________ S - O ___________ (b) Define electroneganivity : (c) Circle the more electronegative atom in each pair: Mg or Ca B or O Cs or N (d) Balance the reaction for the isolation of silicon : SiCl4 + Mg ————> MgCl2 If 3 mol of SiCl4 are reacted, ________mol MgCl2 Li or C + Si _________ mol Mg are needed and and __________ mol Si are produced. (e) A reaction is ran to produce a drug and 10.89 g of the drug is isolated. Using a balanced equation, the chemist calculates that if the reaction went perfect, 12.90 g of the drug would form. Calculate the percent yield for this reaction. ****************************************************************************** Electronegativities of selected elements H = 2.1 Na = 0.9 Mg = 1.2 C = 2.5 N = 3.0 O = 3.5 F = 4.0 Ti = 1.5 Si = 1.8 P = 2.1 S = 2.5 C l = 3.0 2. Acetaminophen, C8H9NO2, is the active ingredient in Tylenol and is widely used as an aspirin substitute. An extra strength Tylenol tablet contains of 500 mg of acetaminophen. (a) What is the formula weight of acetaminophen.? (b) How many moles of acetaminophen are in a tablet? (c) How many individual acetaminophen molecules are in the tablet? (Avogadro’s number = 6.02 x 1023) (d) How many moles of carbon atoms are in a tablet? 3. Predict the formula of the ionic compound formed by the following elements or ions. For the elements, you must determine the charge from the position in the periodic table. Cation Anion Formula (a) sodium fluorine ________________ (b) aluminum hydroxide ________________ (c) magnesium sulfur ________________ (d) ammonium sulfate ________________ (e) potassium hydroxide ________________ (f) lithium carbonate ________________ 4. Disulfur dichloride, S2Cl2, has a revolting smell and it can be used in the vulcanization of rubber. (Vulcanization is a process that makes rubber stronger.) It can be prepared by the following reaction : 3SCl2 + 4NaF ————> SF4 + S2Cl2 + 4NaCl Determine what mass (g) of sodium fluoride that is required is required to completely react with 32.7 g of sulfur dichloride, SCl2? 5. Draw a valid Lewis structure for the following molecules of ions. (a) SO3 (b) NH3 (c) HClO2 (H is bound to O) (Cl between O's) (d) SO32- (e) CH3OH (has O-H bond) (f) H2CO (C is central) 6. Balance the following equations: (a) Cr + (b) SiO2 + (c) NaNO3 + O2 ————> C ————> H2SO4 ————> (d) H2 + (e) C4H8O + Cl2 ————> O2 ————> Cr2O3 Si + CO Na 2SO4 + HNO3 HCl CO2 + H2O 7. Name the following compounds. (a) Al(OH)3 ______________________ (b) Mg(NO3)2 _____________________ (c) NaF ________________________ (d) Ca3(PO4)2 _______________________ (e) FeSO4 _____________________ use a roman numeral (g) Na2S_____________________ (f) AlCl3 __________________________ (h) (NH4)2CO3 __________________________ 8. In each case, Draw a valid Lewis structure describe the shape of the molecule and indicate whether the molecule is polar or not. The total number of valence electrons are in parentheses. Molecule (a) H2O (8e-) shape ________________________________ polar or nonpolar ________________________________ (b) O3 (18 e-) ________________________________ ________________________________ (c) CF4 (32 e-) ________________________________ ________________________________ (d) HCN (10 e-) ________________________________ ________________________________