CHM 130 Exam 2 – Chapters 12, 6, 7, 16, and 8. Version 2

CHM 130 Exam 2 – Chapters 12, 6, 7, 16, and 8 Show all work and clearly mark final answers to receive full credit. 1. (4 pts) Identify what type of bond (ionic or covalent) exists in the following molecules. a. LiF ____ionic_____________ b. CCl4 ______covalent________ c. PBr3 ____covalent_________ d. K3N _____ionic_______ 2. (4 pts) Circle the bonds below that are nonpolar covalent. C–H P – Br I–I C–F 3. (3 pts) Circle the atom or ion that is larger (radius) in each pair: a. Mg or Mg2+ b. O or O2- c. F or Li 4. (14 pts) Draw Lewis dot structures for the following molecules (the central atom is underlined). Then answer the five questions below each molecule. a. SO3 b. CH2Cl2 Number of valence electrons: ___24_____ ABE notation: __AB3_______ Molecular geometry: __triogonal planar____ Bond angles: ____120o_____ Polar molecule? ____no_______ Number of valence electrons: ___20______ ABE notation: ___AB4______ Molecular geometry: ____tetrahedral____ Bond angles: ___109.5o_____ Polar molecule? ____yes__________ 5. (12 pts) Nomenclature: Complete the table below by writing correct names for given formulas or correct formulas for given names. Formulas Names SO2 sulfur dioxide Li2SO4 lithium sulfate CoP cobalt (III) phosphide MgF2 magnesium fluoride HBr (aq) hydrobromic acid NiS nickel (II) sulfide page 1 of 3 6. (6 pts) Write a balanced chemical equation (including physical states) for the following reaction: solid phosphorus reacts with oxygen gas to produce solid diphosphorus trioxide. 4 P (s) + 3 O2 (g)  2 P2O3 (s) 7. (9 pts) Balance the following chemical equations: a. __3__ S (s) + __2__ O3 (g)  __3__ SO2 (g) b. __1__ CH4 (g) + __2__ O2 (g)  __1__ CO2 (g) + __2__ H2O (g) c. __2__ H2 (g) + __1__ SO2 (g)  __2__ H2O (g) + __1__ S (s) d. __1__ CS2 (g) + __3__ O2 (g)  __1__ CO2 (g) + __2__ SO2 (g) 8. (4 pts) Identify the type of reaction for each equation shown below. Your choices are Combination (C), Decomposition (D), Combustion (CB), Single-Replacement (SR), Double-Replacement (DR), and Acid-Base Neutralization (AB) a. Rxn type: ___AB____ 3 NaOH (aq) + H3PO4 (aq)  Na3PO4 (aq) + 3 H2O (l) b. Rxn type: ___SR_____ 3 Mg (s) + Fe2O3 (s)  2 Fe (s) + 3 MgO (s) c. Rxn type: ___CB_____ C2H4 (g) + 3 O2 (g)  2 CO2 (g) + 2 H2O (g) d. Rxn type: ___D_____ 2 PbSO4 (s)  2 PbSO3 (s) + O2 (g) 9. (6 pts) Predict products, including physical states, and balance each equation. a. __2__ HF (aq) + ____ Ba(OH)2 (aq)  __BaF2 (aq) + 2 H2O (l)________ b. ____ Fe (s) + ___ Ni(NO3)2 (aq)  ____Fe(NO3)2(aq) + Ni(s)_______ c. ____ Na2CO3 (aq) + ____ Cu(NO3)2 (aq)  ___CuCO3 (s) + 2 NaNO3 (aq)______ 10. (5 pts) Circle all of the following metals that will react with NaNO3. Ca Fe K Au Na 11. (5 pts) Circle all of the compounds below that will be soluble in water. PbCl2 BaBr2 Ag2SO4 Na2SO4 MgS 12. (4 pts) Identify what element is oxidized, reduced, the oxidizing agent, and the reducing agent for the balanced equation below. Zn (s) + 2 H+ (aq)  H2 (g) + Zn2+ (aq) Oxidized: ____Zn_____________ Oxidizing agent: ____H+____________ Reduced: _________H+______________ Reducing agent: _____Zn____________ page 2 of 3 13. (3 pts) Complete the energy diagram below, labeling 1) transition state, 2) activation energy, and 3) overall energy change (H) on your graph. Bonus: 2 points. Is the reaction shown endothermic or exothermic? ___exothermic___________ Transition State Ea Reactants H Products __C__ 14. (3 pts) Which one of the following will NOT speed up a reaction? a. increase the reactant concentration b. increase the temperature c. increase the product concentration d. add a catalyst 15. (2 pts) How many atoms are in 1 mole of lithium? ___6.02 x 1023_______ 16. (3 pts) How many moles are in 5.46 x 1024 molecules of oxygen gas? 5.46 x 1024 molecules O2 (1 mole / 6.02 x 1023 atoms) = 9.07 moles O2 17. (3 pts) How many moles are in 15.4 grams of argon? 15.4 g Ar (1 mole / 39.95 g) = 0.385 mol Ar 18. (3 pts) What is the molar mass of Cu(NO3)2, with correct units! Cu: 63.55; NO3: 14.01 + 3(16.00) = 62.01 63.55 + 2(62.01) = 187.57 g/mol 19. (4 pts) How many grams of chlorine are in 5.875 liters of bromine gas at STP? 5.875 L (1 mol / 22.4 L) (159.8 g / 1 mol) = 41.91 g of Br2 20. (3 pts) Calculate the density of steam (water vapor) at STP. D = molar mass / molar volume = 18.02 g/mol / 22.4 L/mol = 0.804 g/L page 3 of 3