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Northwest Vista College Chem 1311 - General Chemistry I Summer 2012 Practice __d_ 1. The empirical formula of a compound of uranium and fluorine that is composed of 67.6% uranium and 32.4% fluorine is a) U2F b) U3F4 c) UF4 d) UF6 e) UF8 __b_ 2. A compound was discovered whose composition by mass is 85.6% C and 14.4% H. Which of the following could be the molecular formula of this compound? a) CH4 b) C2H4 c) C3H4 d) C2H6 e) C3H8 __2_ 3. What is the coefficient of H2O when the following equation is properly balanced with the smallest set of whole numbers? ___ Na + ___ H2O a) b) c) d) e) _d__ ___ NaOH + ___ H2 1 2 3 4 5 4. What is the coefficient preceding O2 when the following combustion reaction of a fatty acid is properly balanced using the smallest set of whole numbers? __ C18H36O2 + __ O2 a) b) c) d) e) 1 8 9 26 27 __ CO2 + __ H2O __b_ 5. Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor: 4NH3 + 5O2 4NO + 6H2O When 40.0 g NH3 and 50.0 g O2 are allowed to react, which is the limiting reagent? a) NH3 b) O2 c) NO d) H2O e) No reagent is limiting. ____ When a 0.952 g sample of an organic compound containing C, H, and O is burned completely in 6. oxygen, 1.35 g of CO2 and 0.826 g of H2O are produced. What is the empirical formula of the . compound? ___e_ 7. The complete combustion of 2.0 moles of butane gas, C4H10, will a. consume 13 mol O2 and produce 8.0 mol H2O. b. consume 5.0 mol O2 and produce 13 mol CO2. c. consume 7.0 mol O2 and produce 8.0 mol CO2. d. produce 8 mol CO2 and 5.0 mol H2O. e. consume 13 mol O2 and produce 8.0 mol CO2. ___c_ 8. The reaction of 10.0 g H2 with 10.0 g O2 yields 7.81 g H2O. What is the percent yield of this reaction? a. 34.7% b. 39.1% c. 69.4% d. 78.1% e. 139% ____ 9. Disulfur dichloride can be made by reacting chlorine gas with molten sulfur. S8(l) + 4 Cl2(g) 4 S2Cl2(g) What is the percent yield if 4.88 g S2Cl2 is isolated from the reaction of 10.0 g S8 and 6.00 g Cl2? a. 11.4% b. 16.9% c. 21.1% d. 23.2% e. 42.7% __d_ 10. Which one of the following solutions will have the highest electrical conductivity? a. 0.010 M KCl b. 0.010 M CaI2 c. 0.010 M MgSO4 d. 0.010 M Al(NO3)3 e. 0.010 M Na2SO4 __a_ 11. Which statement about the reaction below is correct? K2SO4 + Ba(NO3)2 BaSO4 + 2 KNO3 a. BaSO4 will precipitate. b. KNO3 will precipitate. c. Both BaSO4 and KNO3 will precipitate. d. Neither BaSO4 nor KNO3 will precipitate. e. No reaction will occur because K2SO4 is insoluble. _b__ 12. Which of the following compounds is a weak acid? a. HCl b. HF c. HBr d. HNO3 e. HClO4 _d__ 13. Which of the following chemical equations represent oxidation-reduction reactions? 1) Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) 2) SrO(s) + H2O() Sr(OH)2(aq) 3) AgNO3(aq) + NaI(aq) AgI(s) + NaNO3(aq) a. 1 b. 2 c. 1 and 2 d. 1 and 3 e. 2 and 3 ___d_ 14. Classify the reaction below. FeCl3(aq) + 3 NaOH(aq) Fe(OH)3(s) + 3 NaCl(aq) a. gas forming b. oxidation-reduction c. acid-base d. precipitation e. decomposition __e__ 15. If 4.39 g AlCl3 is dissolved in enough water to make exactly 100.0 mL of solution, what is the molar concentration of chloride ion? a. 0.0234 M b. 0.0934 M c. 0.110 M d. 0.132 M e. 0.988 M __b__ 16. Which of the following directions correctly describe the preparation of 0.500 L of 0.150 M NaOH from a 6.00 M stock solution? a. Dilute 0.200 L of 6.00 M NaOH to a volume of 0.500 L. b. Dilute 12.5 mL of 6.00 M NaOH to a volume of 0.500 L. c. Combine 0.200 L of 6.00 M NaOH with 0.500 L of water. d. Dilute 475 mL of 6.00 M NaOH to a volume of 0.500 L. e. Combine 12.5 mL of 6.00 M NaOH with 0.500 L of water. __d__ 17. Potassium hydrogen phthalate (KHP) is a weak acid that is used to standardize sodium hydroxide according to the net ionic equation below. HC8H4O4-(aq) + OH-(aq) H2O(l) + C8H4O42-(aq) If 1.02 g KHP (molar mass = 165.05 g/mol) is titrated with 28.34 mL of NaOH, what is the concentration of NaOH? a. 0.03536 M b. 0.1385 M c. 0.2004 M d. 0.2176 M e. 0.2713 M D 21. What is the average mass, in grams, of one arsenic atom? A) 5.48 x 10–23 g B) 33.0 g C) 74.9 g D) 1.24 x 10–22 g E) 8.04 x 1021 g D 22. What is the mass of 7.80 x 1018 carbon atoms? A) 1.30 x 10–5 g B) 6.43 x 103 g C) 7.80 x 1018 g D) 1.56 x 10–4 g E) 12.01 g E 23. How many atoms are in 5.54 g of F2? A) 6.02 x 1023 atoms B) 0.146 atoms C) 0.292 atoms D) 8.78 x 1022 atoms E) 1.76 x 1023 atoms A 24. The percent composition by mass of an unknown chlorinated hydrocarbon was found to be 37.83% C, 6.35% H, and 55.83% Cl by mass. What is the empirical formula of this compound? A) C2H4Cl B) C3H7Cl C) C3H6Cl2 D) C4H9Cl E) C5H11Cl E 25. Which one of the following chemical reactions is balanced? A) HCl + KMnO4 Cl2 + MnO2 + H2O + KCl B) HCl + KMnO4 Cl2 + MnO2 + 2H2O + KCl C) 2HCl + 2KMnO4 Cl2 + MnO2 + 2H2O + 2KCl D) 6HCl + 2KMnO4 2Cl2 + 2MnO2 + 4H2O + 2KCl E) 8HCl + 2KMnO4 3Cl2 + 2MnO2 + 4H2O + 2KCl C 26. Balance the equation below using the smallest set of whole numbers. What is the coefficient of H2O? ___ PCl3(l) + ___ H2O(l) ___ H3PO3(aq) + ___ HCl(aq) A) 1 B) 2 C) 3 D) 5 E) none of these B 27. Balance the following equation using the smallest set of whole numbers, then add together the coefficients. The sum of the coefficients is ___ Cr + ___ H2SO4 ___ Cr2(SO4)3 + ___ H2 A) 4. B) 9. C) 11. D) 13. E) 15. II. Write properly balanced equations the following chemical reactions: 28. P4O10 + 6H2O H3PO4 29. 2Al(s) + 3Co(NO3)2(aq) 2Al(NO3)3(aq) +3 Co(s) 30. C3H6O +4 O2 3CO2 + 3H2O 31. (2 pts) Identify each of the following substances as a strong electrolyte, weak electrolyte, or nonelectrolyte: a) H2O non b) KCl strong c) CH3COOH weak d) C12H22O11 non 32. (1 pts) Characterize the following compounds as soluble or insoluble in water: a) Ca3(PO4)2 insol b) Mn(OH)2 insol c) AgClO3 sol d) K2S sol 33. (3 pts) Write ionic & net ionic equations for the following reactions, include state labels: a) AgNO3 (aq) + Na2SO4 (aq) Ag2 SO4 (s) + 2NaNO3 (aq) Net: 2Ag+ + SO42+ = Ag2 SO4 (s) 34. b) BaCl2 (aq) + ZnSO4 (aq) Products are insoluble Barium Sulfate and Zinc chloride c) (NH4)2CO3 (aq) + CaCl2 (aq) Products are ammonium chloride and insoluble calcium carbonate (1 pts) Identify each of the following species as a Brønsted acid, base, or both: a) HI Bronsted acid b) CH3COO- Bronsted base c) H2PO4- both d) HSO4- both 35. (3 pts) Balance the following equations and write the corresponding net ionic equations (if appropriate): HINTS: (HBr is a strong acid) (Ba(OH)2 is a strong base) (H3PO4 is a weak acid) (Mg(ClO4)2 is soluble) a) ____ HBr (aq) + ____ NH3 (aq) b) ____ Ba(OH)2 (aq) + ____ H3PO4 (aq) c) ____ HClO4 (aq) + _____ Mg(OH)2 (s) Answer key scans to follow soon 36. (4 pts) For the complete redox reactions given here, (i) break down each reaction into its half-reactions; (ii) identify the oxidizing agent; (iii) identify the reducing agent. a) 2Sr + O2 2SrO b) 2Li + H2 2LiH c) 2Cs + Br2 2CsBr d) 3Mg + N2 Mg3N2 37. (3 pts) Give the oxidation number of the underlined atoms in the following molecules & ions: a) ClF g) NaHCO3 b) IF7 c) CH4 i) NaIO3 d) K2CrO4 j) KO2 e) K2Cr2O7 k) PF6- f) KMnO4 l) KAuCl4 h) Li2 38. (1 pts) Calculate the mass of KI in grams required to prepare 5.00 x 102 mL of 2.80 M solution. 39. (1 pts) How many moles of MgCl2 are present in 60.0 mL of 0.100 M MgCl2 solution? 40. (2 pts) Calculate the molarity of each of the following solutions: a) 29.0 g of ethanol (C2H5OH) in 545 mL of solution b) 9.00 g of sodium chloride (NaCl) in 86.4 mL of solution 41. (1 pts) How would you prepare 60.0 mL of 0.200 M HNO3 from a stock solution of 4.00 M HNO3? 42. (1 pts) How many grams of NaCl are required to precipitate most of the Ag+ ions from 2.50 x 102 mL of 0.0113 M AgNO3 solution? Write the net ionic equation for the reaction. 43. (1 pts) A quantity of 18.68 mL of KOH solution is needed to neutralize 0.4218 g of KHP. What is the concentration (in molarity) of the KOH solution? (KHP - potassium hydrogen phthalate, KHC8H4O4) 44. (1 pts) Iron(II) can be oxidized by an acidic K2Cr2O7 solution according to the net ionic equation: Cr2O72- + 6Fe2+ + 14H+ 2Cr3+ + 6Fe3+ + 7H2O If it takes 26.0 mL o 0.0250 M K2Cr2O7 to titrate 25 mL of a solution containing Fe2+, what is the molar concentration of Fe2+? 45. A chemistry student determined the empirical formula for titanium sulfide (TixSy). To do so, she reacted titanium with excess sulfur in a crucible, and got the following data: Weight of empty crucible 11.120 g Weight of titanium 8.820 g Weight of crucible and product 31.700 g What is the empirical formula of titanium sulfide?