CHEM 14103 University Chemistry I Practice Material for Exam 3 Fall 2024 PDF

CHEM 14103: University Chemistry I, Practice Material for Exam 3 1 1. Draw the best Lewis structure for CH3COOH. Include all lone pairs of electrons and nonbonding electrons. a.) What is the hybridization for each of the three interior atoms: CH3COOH C (underlined):...

CHEM 14103: University Chemistry I, Practice Material for Exam 3 1 1. Draw the best Lewis structure for CH3COOH. Include all lone pairs of electrons and nonbonding electrons. a.) What is the hybridization for each of the three interior atoms: CH3COOH C (underlined): C (bold): O(bold): b.) Which one of the following correctly describes the component(s) of the bond between the central carbon and interior oxygen (in bold): CH3COOH ⃝ σ: C(sp2)-O(sp3) ⃝ σ: C(sp2)-O(sp2) ⃝ π: C(sp2)-O(sp3) ⃝ σ: C(sp2)-O(sp) ⃝ σ: C(sp2)-O(p) ⃝ π: C(sp2)-O(p) ⃝ σ: C(sp3)-O(sp3) ⃝ σ: C(sp3)-O(sp2) ⃝ π: C(sp3)-O(p) ⃝ σ: C(sp3)-O(sp) ⃝ σ: C(sp3)-O(p) ⃝ π: C(sp3)-O(sp3) ⃝ σ: C(p)-O(sp2) ⃝ σ: C(p)-O(p) ⃝ π: C(p)-O(p) c.) Which one of the following correctly describes component(s) of the bond between the central carbon and peripheral oxygen (in bold): CH3COOH ⃝ σ: C(sp2)-O(sp3) ⃝ σ: C(sp2)-O(sp2) ⃝ π: C(sp2)-O(sp3) ⃝ σ: C(sp2)-O(sp) ⃝ σ: C(sp2)-O(p) ⃝ π: C(sp2)-O(p) ⃝ σ: C(sp3)-O(sp3) ⃝ σ: C(sp3)-O(sp2) ⃝ π: C(sp3)-O(p) ⃝ σ: C(sp3)-O(sp) ⃝ σ: C(sp3)-O(p) ⃝ π: C(sp3)-O(sp3) ⃝ σ: C(p)-O(sp2) ⃝ σ: C(p)-O(p) ⃝ π: C(p)-O(p) d.) Which one of the following correctly describes the component(s) of the bond between the left carbon and a hydrogen atom: CH3COOH ⃝ σ: C(sp2)-H(s) ⃝ σ: C(sp2)-H(sp3) ⃝ π: C(sp3)-H(s) ⃝ σ: C(sp3)-H(s) ⃝ σ: C(sp3)-H(sp3) ⃝ π: C(sp2)-H(s) ⃝ σ: C(sp3)-H(p) ⃝ π: C(sp3)-H(sp3) ⃝ π: C(sp3)-H(p) e.) Which one of the following correctly describes the component(s) of the bond between the oxygen atom in bold and the hydrogen atom: CH3COOH ⃝ σ: O(sp2)-H(s) ⃝ σ: O(sp2)-H(sp3) ⃝ π: O(sp3)-H(s) ⃝ σ: O(sp3)-H(s) ⃝ σ: O(sp3)-H(sp3) ⃝ π: O(sp2)-H(s) ⃝ σ: O(sp3)-H(p) ⃝ π: O(sp3)-H(sp3) ⃝ π: O(sp3)-H(p)  CHEM 14103: University Chemistry I, Practice Material for Exam 3 2 2. Indicate the hybridization on the central atom for each species. a.) NF3 b.) PF5 c.) ClF3 d.) IF5 e.) XeF2 3. Which of the following is/are true according to valence bond theory? Select all that apply. ⃝ A chemical bond is the overlap of two half-filled atomic orbitals on neighboring atoms and spin-pairing of the two electrons ⃝ In methane, CH4, the four hybrid orbitals on carbon are degenerate ⃝ A triple bond is composed of one σ component and two π components ⃝ The σ component of a double bond is generally weaker than the π component of the double bond ⃝ Hybridization is the process of combining two or more atomic orbitals on neighboring atoms to create hybrid atomic orbitals that span multiple atoms 4. Which of the following is/are true? Select all that apply. Consider the molecule below, first filling in multiple bonds and lone pairs of electrons so that each atom has a formal charge of 0. ⃝ Carbon II would use its sp2 hybrid orbitals to form sigma bonds to the carbons and the oxygen, while using its unhybridized p orbital to form the pi bond to the oxygen. ⃝ Carbon III is sp hybridized; it uses its unhybridized p orbitals to complete its bonding with the nitrogen through pi bonding. ⃝ There is a total of three pi bonds in this molecule. ⃝ There are four sp3 hybridized carbons in this molecule.  CHEM 14103: University Chemistry I, Practice Material for Exam 3 3 5. Which of the following is/are true according to valence bond theory? Select all that apply. ⃝ When four atomic orbitals are added together, the same number of hybrid orbitals must be formed. ⃝ In carbon tetrachloride, CCl4, the four hybrid orbitals on carbon are degenerate and form only sigma bonds. ⃝ A triple bond is composed of two σ components and one π component. ⃝ In sp hybridization, one standard p atomic orbital remains and three sp hybrid orbitals are formed. 6. Which of the following is/are true according to valence bond theory? Select all that apply. ⃝ The hybridization of C atom in formic acid, HCOOH is sp. ⃝ The hybridization of the N atom in NH3 is sp3. ⃝ The S atom in SF6 presents sp3d2 hybridization and its molecular geometry is octahedral. ⃝ The hybridization of the C atom in HCN is sp. ⃝ The hybridization of each C in CH3CH2OH (from left to right) is, 1st C sp3; 2nd C sp2. 7. This structure of thymine does not show lone pairs of electrons (you will need to fill them in so that every atom has a formal charge of 0). Fill in the boxes with the hybridization of the indicated atoms.  CHEM 14103: University Chemistry I, Practice Material for Exam 3 4 8. Which of the following is/are true according to molecular orbital theory? Select all that apply. Use the diagrams. ⃝ Atomic orbitals on different atoms are combined to produce molecular orbitals spanning multiple atoms. ⃝ Adding electrons to bonding molecular orbitals lowers the overall energy and promotes bonding. ⃝ C22– should have a stronger bond than C2. ⃝ The bond order of C22– is 3. ⃝ C22+ should be diamagnetic. ⃝ O22– should have a shorter bond than O2. ⃝ O22+ should have a bond order of 3. ⃝ B22+ should be stable enough to exist. ⃝ N22+ should have a stronger bond than N2. ⃝ F22+ should be diamagnetic. ⃝ F22– should be stable enough to exist. 9. Which of the following is/are true? Select all that apply. ⃝ The boiling of ethanol, C2H5OH, is a physical change. ⃝ Crushing a rock to powder is a chemical change. ⃝ The viscosity of motor oil is a physical property. ⃝ The flammability of octane is a chemical property. 10. Write a balanced chemical equation for the combustion of gaseous butane (C4H10), which produces carbon dioxide gas and water vapor. What is the sum of the coefficients, including implied 1’s? Select only one answer. ⃝ 16 ⃝ 17 ⃝ 32 ⃝ 33 ⃝ 34  CHEM 14103: University Chemistry I, Practice Material for Exam 3 5 11. Complete the equation below by adding coefficients and products. Write in any implied “1” for coefficients. Write your final answer in the boxes—use the smallest ratio of whole-number coefficients. C12H24SO3(l) + O2(g) → (g) + (g) + carbon dioxide dihydrogen monoxide (g) sulfur dioxide 12. Aqueous potassium phosphate reacts with aqueous lead(II) acetate in a precipitation reaction. Fill in the boxes with coefficients and chemical formulas to balance the reaction. potassium phosphate lead(II) acetate (aq) + (aq) → (s) + (aq) lead(II) phosphate potassium acetate 13. What mass of CO2 in kg is produced when 14.0 L of octane (C8H18) react completely with oxygen according to the following balanced equation. The density of octane is 0.703 g/mL. Give your answer to 3 significant figures. 2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(g) kg CO2  CHEM 14103: University Chemistry I, Practice Material for Exam 3 6 14. Which substance is the limiting reactant when 2.0 g of sulfur reacts with 3.0 g of oxygen and 4.0 g of sodium hydroxide according to the following chemical equation? Select only one answer. 2 S(s) + 3 O2(g) + 4 NaOH(aq) → 2 Na2SO4(aq) + 2 H2O(l) ⃝ None of these substances is the limiting reactant. ⃝ O2(g) ⃝ S(s) ⃝ NaOH (aq) ⃝ Na2SO4(aq) ⃝ H2O(l) 15. A reaction vessel contains 84.03 g N2 and 104.1 g Li, which reacts to form Li3N: N2(g) + 6 Li(s) → 2 Li3N(s) a.) If 142 g of Li3N is actually produced when the reaction is performed, calculate the percent yield. Give your answer with 3 significant figures. % b.) Calculate the mass of excess reactant remaining. Give your answer with 3 significant figures. g  CHEM 14103: University Chemistry I, Practice Material for Exam 3 7 16. A reaction mixture initially contains 275 g oxygen gas and 355 g zinc sulfide. The reaction is as follows: 3 O2(g) + 2 ZnS(s) → 2 ZnO(s) + 2 SO2(g) a.) If the reaction is performed and 184 g sulfur dioxide is actually produced, what is the percent yield? Give your answer to 3 significant figures. % b.) What mass of excess reactant remains after the reaction has gone to completion? Give your answer to 3 significant figures. g 17. What is the percent yield of the reaction if 85.6 mL PCl3 (density = 1.57 g/mL) is actually produced when the reaction is performed with 125 g Cl2? Give your answer to 3 significant figures. P4(s) + 6 Cl2(g) → 4 PCl3(l) %  CHEM 14103: University Chemistry I, Practice Material for Exam 3 8 18. What mass of solid carbon is required to actually produce 15.0 g SiC if the percent yield for the reaction that follows is 75.0%? Give your answer with 3 significant figures. 3 C(s) + SiO2(s) → SiC(s) + 2 CO(g) gC 19. What mass of O2 gas is required to actually produce 56.0 g SO2 gas if the percent yield for the reaction that follows is 65.0%? Give your answer with 3 significant figures. 2 H2S(g) + 3 O2(g) → 2 H2O(l) + 2 SO2(g) g O2 20. If 76.8 grams of oxygen gas and 80.1 grams of aluminum are in a reaction mixture and the % yield for the reaction is 82.5%, how many grams of aluminum oxide will be produced? Balance first: ___O2(g) + ___Al(s) → ____Al2O3(s) Give your answer with 3 significant figures. g  CHEM 14103: University Chemistry I, Practice Material for Exam 3 9 21. What volume (in mL) of 0.750 M Fe(NO3)3 stock solution is needed to create 150.0 mL of solution with an ion concentration of 0.250 M NO3–? Give your answer to 3 significant figures. mL 22. Calculate the molarity of potassium ions in the final solution if 75.0 mL of 0.800 M potassium phosphate is added to 125 mL of 0.600 M potassium sulfate. Give your answer with 3 significant figures. M K+ 23. What volume of 0.250 M Na3PO4 contains 4.95 g sodium? Give your answer to 3 significant figures. mL 24. You would like to create 80.0 mL of 0.900 M HCl from 12.0 M HCl stock solution. What volume of stock solution will be needed? Give your answer to 3 significant figures. mL  CHEM 14103: University Chemistry I, Practice Material for Exam 3 10 25. A student prepared a stock solution by dissolving 138.0 g of solid potassium phosphate in enough water to make 500.0 mL of solution. What volume of this potassium phosphate stock solution is needed to create 250.0 mL of solution with a potassium ion concentration of 0.800 M? Give your answer with 3 significant figures. mL 26. What volume of 0.156 M Na3PO4 solution is necessary to completely react with 90.7 mL of 0.118 M CuCl2? Give your answer with 3 significant figures. 2 Na3PO4(aq) + 3 CuCl2(aq) → Cu3(PO4)2(s) + 6 NaCl(aq) mL 27. What volume of 0.350 M lead(II) nitrate solution is required to completely react with 65.0 mL of 0.100 M aluminum chloride solution? Balance first: ___Pb(NO3)2(aq) + ___AlCl3(aq) → ___PbCl2(s) + ___Al(NO3)3(aq) Give your answer with 3 significant figures. mL  CHEM 14103: University Chemistry I, Practice Material for Exam 3 11 28. What volume of 0.200 M Al(NO3)3 is needed to produce 0.560 g of aluminum carbonate? Give your answer to 3 significant figures. 3 K2CO3(aq) + 2 Al(NO3)3(aq) → Al2(CO3)3(s) + 6 KNO3(aq) mL 29. What volume of 0.600 M K2CO3 is needed to completely react with 12.0 mL 0.800 M Fe(C2H3O2)3? Give your answer to 3 significant figures. 3 K2CO3(aq) + 2 Fe(C2H3O2)3(aq) → Fe2(CO3)3(s) + 6 KC2H3O2(aq) mL 30. A 15.0 mL sample of 0.200 M Na3PO4 is combined with 125 mL 0.0600 M AgNO3. The precipitate (Ag3PO4) is collected and dried and found to have a mass of 0.942 g. Calculate the percent yield. Give your answer to 3 significant figures. Na3PO4(aq) + 3 AgNO3(aq) → Ag3PO4(s) + 3 NaNO3(aq) %  CHEM 14103: University Chemistry I, Practice Material for Exam 3 12 31. Which of the following is/are true? Select all that apply. ⃝ Strong acids, strong bases and soluble salts all are strong electrolytes. ⃝ A weak acid solution fully ionizes, while a strong acid solution only partially ionizes. ⃝ Hydrobromic acid is a strong electrolyte. ⃝ Calcium phosphate is a strong electrolyte. ⃝ A molecular compound that does not ionize at all in solution is considered a weak electrolyte. 32. Which of the following is/are weak electrolyte(s) in solution? Select all that apply. ⃝ HNO3 ⃝ CH4 ⃝ NH3 ⃝ NaC2H3O2 ⃝ HF 33. Aqueous potassium phosphate reacts with aqueous lead(II) acetate in a precipitation reaction. Fill in the boxes with coefficients and chemical formulas to balance the reaction. potassium phosphate lead(II) acetate (aq) + (aq) → (s) + (aq) solid ionic compound aqueous ionic compound 34. a.) Aqueous iron(III) nitrate reacts with aqueous potassium carbonate in a precipitation reaction. Fill in the boxes with coefficients and chemical formulas to balance the reaction for the molecular equation. iron(III) nitrate potassium carbonate (aq) + (aq) → (s) + (aq) solid ionic compound aqueous ionic compound b.) Write the complete ionic equation for the precipitation reaction between aqueous iron(III) nitrate and aqueous potassium carbonate.  CHEM 14103: University Chemistry I, Practice Material for Exam 3 13 c.) Write the net ionic equation for the precipitation reaction between aqueous iron(III) nitrate and aqueous potassium carbonate. 35. a.) What is the sum of the coefficients (including implied 1’s) for the balanced complete ionic equation for the reaction of aqueous barium bromide with aqueous aluminum sulfate? b.) What is the sum of the coefficients (including implied 1’s) for the balanced net ionic equation for the reaction of aqueous barium bromide with aqueous aluminum sulfate? 36. The titration of 25.0 mL of sulfuric acid with an unknown concentration requires 83.6 mL of 0.12 M sodium hydroxide solution. What is the concentration of the sulfuric acid solution (in M)? Give your answer with 3 significant figures. HINT: Write a balanced equation first. M  CHEM 14103: University Chemistry I, Practice Material for Exam 3 14 37. Which of the following acids is/are name correctly? Select all that apply. ⃝ HBrO hypobromous acid ⃝ H2S hydrosulfuric acid ⃝ H3PO4 phosphoric acid ⃝ HClO2 chloric acid ⃝ HBr hydrobromous acid ⃝ H2CO3 hydrocarbonic acid 38. a.) Write the molecular equation for the acid-base reaction between aqueous phosphoric acid and aqueous sodium hydroxide. b.) Write the complete ionic equation for the acid-base reaction between aqueous phosphoric acid and aqueous sodium hydroxide. c.) Write the net ionic equation for the acid-base reaction between aqueous phosphoric acid and aqueous sodium hydroxide. 39. a.) Write the molecular equation for the acid-base reaction between aqueous hydrobromic acid and aqueous potassium hydroxide. b.) Write the complete ionic equation for the acid-base reaction between aqueous hydrobromic acid and aqueous potassium hydroxide.  CHEM 14103: University Chemistry I, Practice Material for Exam 3 15 c.) Write the net ionic equation for the acid-base reaction between aqueous hydrobromic acid and aqueous potassium hydroxide. 40. Aqueous sodium carbonate reacts with aqueous hydrochloric acid. Fill in the boxes with coefficients and chemical formulas to balance the reaction (pay attention to the states of matter to put the products in the right boxes!). sodium carbonate hydrochloric acid (aq) + (aq) → (l) + (g) + (aq) 41. Indicate the oxidation state for each element in the following: a.) H2O2 H: O: b.) hypochlorite Cl: O: c.) O3(g) O: d.) xenon tetrafluoride Xe: F: 42. Considering the following reaction, which of the following is/are true? Select all that apply. Cr2O72− + 3 HNO2 + 5 H+ → 2 Cr3+ + 3 NO3− + 4 H2O ⃝ The O and H atoms do not change oxidation state in this reaction. ⃝ N is oxidized in this reaction. ⃝ The N in NO3− ion has an oxidation state of –3. ⃝ The Cr in Cr2O72− ion serves as the reducing agent. ⃝ Cr has an oxidation state of +6 in Cr2O72−  CHEM 14103: University Chemistry I, Practice Material for Exam 3 16 43. Considering the following reactions, which of the statements is/are true? Select all that apply. KNO2 + 3 Zn + 5 H2O → NH3 + KOH + 3 Zn(OH)2 ⃝ The oxygen and hydrogen atoms do not change oxidation state in this reaction ⃝ Zinc has an oxidation state of +2 in Zn(OH)2. ⃝ The nitrogen in KNO2 serves as the reducing agent. ⃝ Zinc gains electrons in this reaction. ⃝ The nitrogen in NH3 has an oxidation state of -3. 44. For the redox reaction: 3 H2SO4(aq) + 2 Al(s) → 3 H2(g) + Al2(SO4)3(aq) a.) Fill in the table for the oxidation states of each element for reactants and products. Oxidation Oxidation Element state as state as reactant product H S O Al b.) The element that undergoes oxidation is… ⃝ H ⃝ S ⃝ O ⃝ Al c.) The element that undergoes reduction is… ⃝ H ⃝ S ⃝ O ⃝ Al c.) The reducing agent is… ⃝ H2SO4(aq) ⃝ Al(s) ⃝ H2(g) ⃝ Al2(SO4)3(aq) d.) The oxidizing agent is… ⃝ H2SO4(aq) ⃝ Al(s) ⃝ H2(g) ⃝ Al2(SO4)3(aq) 45. A gas is compressed from an initial volume of 5.50 L to a final volume of 1.45 L by an external pressure of 1.00 atm. During the compression the gas releases 126 J of heat. What is the change in internal energy of the gas? Give your answer with 3 significant figures. HINT: 1 L atm = 101.3 J. J  CHEM 14103: University Chemistry I, Practice Material for Exam 3 17 Given on exam (do not bring a physical copy of this to the exam): 101.3 J = 1 L atm E = q + w where w = −PV q = (mass) (specific heat) (T)