CHEM 10050 Supplemental Problem Set #2 1. Draw Lewis Structures and predict the molecular geometry for the following molecules. Also, label each formula as “ionic, polar covalent or non-polar covalent”. a) CH2O b) HCN c) NaBrO3 O O Na+ O C H H trigonal planar polar covalent d) K3PO4 Br O H C N: linear polar covalent pyramidal ionic e) C2H2 f) HSCN 3 O K+ K+ H O P + K O H C C C N H linear non-polar covalent O S bent linear polar covalent tetrahedral ionic g) SO3 h) CH3NO O C O S O i) HCNO O trigonal planar non-polar H N trigonal planar H H pyramidal H C N O linear polar covalent polar 2. 25.0 g of butane (C4H10) was burned in a combustion reaction. How many grams of carbon dioxide were produced? 2C4H10 + 13O2 8CO2 + 10H2O 25.0 g butane x 8 mol CO2 44.0 g CO2 1mol butane x x 75.7 g CO2 58.12 g butane 2 mol butane 1mol CO2 3. 12.56 g of nitric acid was reacted with sodium carbonate in a double displacement reaction. How many grams of carbon dioxide were produced? Na2CO3 + 2HNO3 CO2 + H2O + 2NaNO3 12.56 g Na 2CO3 x 1 mol HNO3 1 mol CO2 44.01 g CO2 x x 4.396 g CO2 63.01 g HNO3 2 mol HNO3 1 mol CO2 4. The Haber Process for the synthesis of ammonia involves the reaction of hydrogen gas with nitrogen gas in a combination reaction. How many grams of hydrogen gas is needed to produce 50.0 g of ammonia? 3H2 + N2 2NH3 50.0 g NH3 x 1mol NH3 3 mol H2 2.016 g H2 x x 8.88 g H2 17.03 g NH3 2 mol NH3 1mol H2 5. Chlorine gas reacts with aluminum bromide in a single displacement reaction. How many milliliters of bromine would be produced from 125.0 g of aluminum bromide? (dBr2 = 3.14 g/ml) 2AlBr3 + 3Cl2 2AlCl3 + 3Br2 125.0 g AlBr3 x 1mol AlBr3 3 mol Br2 159.8 g Br2 1ml Br2 x x x 35.8 ml Br2 266.69 g AlBr3 2 mol AlBr3 1mol Br2 3.14 g Br2 6. Balance the following equations. Identify the redox reactions and label the reducing and oxidizing agents. a) Na(s) + H2O(l) H2(g) + NaOH(aq) 2Na(s) + 2H2O(l) H2(g) + 2NaOH(aq) Na – reducing agent H2O – oxidizing agent b) H3PO4(aq) + NaOH(aq) H2O(l) + Na3PO4(aq) H3PO4(aq) + 3NaOH(aq) H2O(l) + Na3PO4(aq) Not a redox reaction! c) Al(s) + H2SO4(aq) H2(g) + Al2(SO4)3(aq) 2Al(s) + 3H2SO4(aq) 3H2(g) + Al2(SO4)3(aq) Al – reducing agent H2SO4 – oxidizing agent 7. Calculate the volume that would be occupied by 12.0 g carbon dioxide at 720 torr and 28°F. PV = nRT 1mol CO2 1 atm 0.947 atm P = 720 torr x n 12.0 g CO2 x 0.273 mol CO2 760 torr 44.0 g CO2 R = 0.0821 L atm mol K T= 28 o F 32 273 271K 1.8 L atm (0.273 mol CO 2 ) 0.0821 (271 K) nRT mol K V 6.41L P (0.947 atm) 8. How many grams of acetylene (C2H2) are contained in a 60 L gas cylinder at 1,650 psi and 73°F? PV = nRT V = 60 L R = 0.0821 P = 1,650 psi x L atm mol K 1 atm 112 atm 14.7 psi 73 o F 32 273 296 K 1.8 PV (112 atm)(60 L) n 277 mol C 2H2 L atm RT 0.0821 (296 K ) mol K T= 277 mol C2H2 x 26.04 g C2H2 7.20 x 103 g C2H2 1mol C2H2 9. 6.75 g of oxygen gas occupies a volume of 3.25 L at 740 torr. What is the Celsius temperature of this gas? PV = nRT V = 3.25 L n 6.75 g O2 x P = 740 torr x 1mol O 2 0.211mol O2 32.0 g O 2 T PV nR 1 atm 0.974 atm 760 torr L atm R = 0.0821 mol K (0.974 atm)(3.25 L) 183 K L atm (0.211mol O 2 ) 0.0821 mol K 10. Draw two resonance forms for the following molecules. Indicate which, if any, resonance form contributes most to the bonding description for the molecule. (Hint: use formal charges) a. CS2 S C S S contributes most C S contributes least b. HN3 H N N N H N N 2 N H N N 11. Define and describe the three basic types of van der Waal’s forces. See Notes 12. Determine formulas from the following names: a) phosphorus pentachloride PCl5 b) iodine heptafluoride IF7 c) tetraphosphorus decasulfide P4S10 d) selenium hexafluoride SeF6 e) dinitrogen tetraoxide N2O4 13. Write an equation for the complete ionization of the following compounds: a) sulfuric acid b) nitric acid H2SO4 2H+ + SO42 HNO3 H+ + NO3 c) calcium hydroxide Ca(OH)2 Ca2+ + 2OH d) aluminum sulfate Al2(SO4)3 2Al3+ + 2SO42 e) phosphoric acid H3PO4 3H+ + PO43 N 14. Balance the following chemical equations and identify each as addition, decomposition, single displacement, double displacement or combustion. a. Au2O3 Au + O2 2Au2O3 4Au + 3O2 decomposition b. Mg Fe3O4 + Fe 4Mg c. FeCl2 FeCl2 d. H3PO4 + Fe(OH)2 + 4MgO NaCl 2NaOH Fe(OH)2 double displacement Ca(OH)2 2H3PO4 e. + MgO Fe3O4 3Fe + single displacement + NaOH + + Ca3(PO4)2 + + H2O + 3Ca(OH)2 Ca3(PO4)2 + double displacement (neutralization) Cd(NO3)2 + H2S CdS + g. C3H8O KBr + + O2 CO2 2C3H8O + Cl2 KCl 2KBr + 2HNO3 H2O 9O2 6CO2 combustion + 6H2O HNO3 Cd(NO3)2 + H2S CdS + double displacement f. 2NaCl + 8H2O Br2 + Cl2 2KCl + single displacement Br2