CHAPTER 3 COMPOUNDS AND MOLECULES

Chapter 3 Compounds and Molecules Page 1 CHAPTER 3 COMPOUNDS AND MOLECULES 3-1. Octane, a component of gasoline, has eight carbon atoms and eighteen hydrogen atoms per molecule. Its formula is written as (a) C 18 H 8 (b) C 8 H 18 (c) C 8 H 18 (d) C 4 H 9 3-2. Glycine, one of the essential amino acids, has two carbon atoms, five hydrogen atoms, two oxygen atoms, and one nitrogen atom per molecule. Its formula is written as (a) C 2 H 5 NO 2 (b) Ca 2 H 5 NO 2 (c) C 2 H 5 NeO 2 (d) CHNO 2 3-3. Some common ions based on Group 1A or alkali metal elements are (a) Na +, Ca 2+, Fe 3+ (b) Na +, Li +, Cs + (c) Li +, Ag +, Au + (d) Ca 2+, Ba 2+, Sr 2+ 3-4. Some common ions based on metals are (a) Li +, Ba 2+, Ni 2+ (b) Li -, Ca 2+, Cu 2+ (c) Li 2+, Ba 3+, Ag 2+ (d) Fe +, Ba 4+, Al 2+ 3-5. Some common ions based on nonmetals are (a) S 2-, Al 3-, Cl 2- (b) Na -, O 2-, F - (c) Ca 2+, Na +, Mg 2+ (d) F -, O 2-, P 3-3-6. Some common ions based on Group 6A elements are (a) O 2+, S 2+, Se 2+ (b) O 2-, S 2-, Se 2- (c) O 2-, N 3-, F - (d) Cl -, O 2+, Al 3+

Chapter 3 Compounds and Molecules Page 2 3-7. Some common polyatomic ions are (a) NO 3 -, O 2-, Al 3+ (b) MnO 4 -, CO 3 2-, H 2 O (c) CO 3 2-, NO 3 -, SO 4 2- (d) CH 3 COO -, Cl -, Fe 3+ 3-8. Match the ions below with their names. Name Formulas (i) Sulfate (a) CH 3 COO - (ii) Acetate (b) - HCO 3 (iii) Nitrate (c) 2- SO 4 (iv) Hydrogen carbonate (d) - NO 3 3-9. Which combination of ion name and formula is correct? (a) nitrite, NO 2 - (b) sulfate, SO 3 2- (c) cyanide, C 2 N 3 - (d) permanganate, MnO 3-3-10. What is the correct formula for a compound formed from the most common ions of aluminum and sulfur? (a) Al 3 S 2 (b) AlS (c) Al 3 S 3 (d) Al 2 S 3 3-11. What is the correct formula for calcium hydroxide? (a) Ca 2 (OH) 2 (b) Ca 2 (OH) (c) Ca(OH) 2 (d) Ca 3 (OH) 4 3-12. What is the correct formula for iron(iii) sulfate? (a) Fe 2 (SO 3 ) 3 (b) Fe 2 (SO 4 ) 3 (c) FeSO 4 (d) Fe 3 (SO 4 ) 2

Chapter 3 Compounds and Molecules Page 3 3-13. Give the ions present and their relative numbers in sodium carbonate. (a) 2 Li + 2- and 1 CO 3 (b) 1 Na + 2- and 1 CO 3 (c) 2 Na + and 1 CO 3 2- (d) 1 Na + and 2 CO 3 2-3-14. What is the correct name for Al 2 (SO 4 ) 3? (a) aluminum sulfide (b) aluminum sulfate (c) aluminum sulfite (d) argon sulfate 3-15. What is the correct formula for cobalt(iii) oxide? (a) Ca 2 O 3 (b) Co 3 O 2 (c) Co 2 O 3 (d) CoO 3-16. What is the correct name for N 2 O, commonly called nitrous oxide or laughing gas? (a) dinitrogen oxide (b) nitrogen oxide (c) nitrogen dioxide (d) nitroxide 3-17. What is the formula for sulfur tetrachloride? (a) S 2 Cl 8 (b) S 4 Cl (c) SCl (d) SCl 4 3-18. Which combination of name and formula below is correct? (a) ammonia, NH (b) HBr, hydrogen bromide (c) sulfur dioxide, SO 3 (d) carbon monoxide, CO 2 3-19. Which combination of name and formula below is correct? (a) sodium acetate, NaCH 3 COO (b) lithium oxide, LiO 2 (c) iron(ii) chloride, FeCl 3 (d) potassium hydrogen sulfate, K 2 SO 4

Chapter 3 Compounds and Molecules Page 4 3-20. Match the names and formulas of compounds below. Names Formulas (i) potassium permanganate (a) Ca(OCl) 2 (ii) sodium hydrogen carbonate (b) K 2 Cr 2 O 7 (iii) potassium dichromate (c) KMnO 4 (iv) calcium hypochlorite (d) NaHCO 3 3-21. Give the ions present and their relative numbers in iron(ii) phosphate. (a) 3 Fe 2+ and 2 PO 4 3- (b) 1 Fe 2+ and 2 PO 4 3- (c) 2 Fe 2+ and 3 PO 4 3- (d) 3 Fe 3+ and 2 PO 4 3-3-22. The molar mass of hydrazine, N 2 H 4, is (a) 4.08 g/mol (b) 28.00 g/mol (c) 16.03 g/mol (d) 32.05 g/mol 3-23. The molar mass of vitamin C, C 6 H 8 O 6, is (a) 29.02 g/mol (b) 230.13 g/mol (c) 176.13 g/mol (d) 72.00 g/mol 3-24. The molar mass of epsom salt, MgSO 4 7 H 2 O, is (a) 120.36 g/mol (b) 246.47 g/mol (c) 138.38 g/mol (d) 126.11 g/mol 3-25. The molar mass of ammonium carbonate is (a) 96.09 g/mol (b) 88.05 g/mol (c) 78.05 g/mol (d) 112.09 g/mol 3-26. The molar mass of aluminum acetate is (a) 86.0 g/mol (b) 204.1 g/mol (c) 77.1 g/mol (d) 102.0 g/mol

Chapter 3 Compounds and Molecules Page 5 3-27. The molar mass of disulfur decafluoride is (a) 127.05 g/mol (b) 358.60 g/mol (c) 222.04 g/mol (d) 254.10 g/mol 3-28. Place the following compounds in order of increasing molar mass: CaCO 3, MgCO 3, and Na 2 CO 3. (a) CaCO 3 < MgCO 3 < Na 2 CO 3 (b) MgCO 3 < Na 2 CO 3 < CaCO 3 (c) MgCO 3 < CaCO 3 < Na 2 CO 3 (d) Na 2 CO 3 < MgCO 3 < CaCO 3 3-29. How many moles are contained in 15.6 g of NH 4 Cl? (a) 0.292 mol (b) 834 g/mol (c) 3.43 mol (d) 0.309 mol 3-30. How many moles are contained in 13.8 g of BaCl 2 2 H 2 O? (a) 17.7 mol (b) 0.0565 mol (c) 0.0610 mol (d) 0.0663 mol 3-31. How many moles are contained in 0.206 g of potassium sulfate? (a) 1.63 x 10-3 mol (b) 846 mol (c) 1.52 x 10-3 mol (d) 1.18 x 10-3 mol 3-32. How many grams are there in 1.36 mol of ethyl alcohol, C 2 O? (a) 0.0160 g (b) 123 g (c) 62.7 g (d) 6.27 g 3-33. How many grams are there in 10.0 g of the beautiful blue compound CuSO 4 5 H 2 O? (a) 0.0401 mol (b) 0.0627 mol (c) 25.0 mol (d) 0.0563 mol

Chapter 3 Compounds and Molecules Page 6 3-34. The density of liquid benzene, C 6, is 0.879 g/cm 3 at 15 C. How many moles are there in 36.5 ml of benzene at 15 C? (a) 2.43 mol (b) 0.467 mol (c) 0.411 mol (d) 0.532 mol 3-35. Place the following in order of increasing mass: 15.0 g of NaCl, 1.00 mol of H 2 O, 0.50 mol of CH 4, and 0.25 mol of NaOH. (a) CH 4 < NaOH < NaCl < H 2 O (b) NaOH < NaCl < H 2 O < CH 4 (c) NaCl < H 2 O < CH 4 < NaOH (d) H 2 O < NaOH < NaCl < CH 4 3-36. You have 1.25 g of malic acid, C 4 O 5, an acid found in apples and other fruits. How many molecules of the acid do you have? (a) 7.53 x 10 23 molecules (b) 5.61 x 10 21 molecules (c) 1.27 x 10 27 molecules (d) 1.78 x 10-22 molecules 3-37. If you need 3.6 x 10 24 molecules of oxalic acid, H 2 C 2 O 4, how many grams of the acid should you weigh out in the laboratory? (a) 0.0019 g (b) 15 g (c) 540 g (d) 270 g 3-38. Which of the following contains the largest number of molecules: 6.00 g CH 4, 9.00 g H 2 O, 11.0 g C 2, or 15.0 g NO 2? (a) H 2 O (b) CH 4 (c) C 2 (d) NO 2 3-39. What is the weight percent of carbon in oxalic acid, H 2 C 2 O 4? (a) 2.24% (b) 26.68% (c) 71.08% (d) 13.34%

Chapter 3 Compounds and Molecules Page 7 3-40. Cyclohexylbenzene has the empirical formula C 3 H 4. Its molar mass is 160.3. Its molecular formula is (a) C 3 H 4 (b) C 6 H 8 (c) C 9 H 12 (d) C 12 H 16 3-41. Maleic acid, which is used to manufacture artificial resins, has the empirical formula CHO. Its molar mass is 116.1 g/mol. What is its molecular formula? (a) CHO (b) C 2 H 2 O 2 (c) C 3 H 3 O 3 (d) C 4 H 4 O 4 3-42. Nitrogen and oxygen form an extensive series of at least seven oxides with the general formula N x O y. One of them is a blue solid that comes apart, reversibly, in the gas phase. It contains 36.84% N. What is the empirical formula of the oxide? (a) N 2 O (b) NO (c) N 2 O 3 (d) NO 2 3-43. Boron forms an extensive series of hydrides. If you isolate a new hydride that is 81.1% B, a possible molecular formula of the compound is (a) B 2 (b) B 3 H 9 (c) B 4 H 10 (d) B 10 H 14 3-44. A compound contains 15.94% boron with the remainder being fluorine. What is the empirical formula of the compound? (a) BF (b) BF 2 (c) B 2 F 3 (d) BF 3 3-45. Elemental sulfur (1.256 g) is combined with fluorine, F 2, to give a compound with the formula SF x, a very stable, colorless gas. If you have isolated 5.722 g of SF x, what is the value of x? (a) 1 (b) 2 (c) 4 (d) 6

Chapter 3 Compounds and Molecules Page 8 3-46. Transition metals can combine with carbon monoxide (CO) to form compounds such as Fe(CO) 5 and Co 2 (CO) 8. Assume that you combine 0.125 g of nickel with CO and isolate 0.364 g of Ni(CO) x. What is the value of x? (a) 1 (b) 2 (c) 3 (d) 4 3-47. Potassium metal (3.91 g) is allowed to react with excess oxygen (O 2 ). The reaction yields 7.11 g of an explosive, yellow solid called a superoxide. What is the empirical formula of the compound? (a) KO (b) KO 2 (c) K 2 O (d) K 2 O 3 3-48. Hydrated salts are very common. If you heat 2.105 g of CoCl 2 x H 2 O, and find that 1.149 g of CoCl 2 remains, what is the value of x? (a) 1 (b) 2 (c) 4 (d) 6 3-49. Citric acid, C 6 H 8 O 7, is found in many fruits. (i) (ii) (iii) What is the weight percent of carbon in the compound? (a) 37.5% (b) 4.2% (c) 58.3% (d) 18.8% If you have 100. mg in a can of soft drink, how many molecules of citric acid does this represent? (a) 6.26 x 10 20 molecules (b) 3.13 x 10 20 molecules (c) 3.13 x 10 24 molecules (d) 3.13 x 10 23 molecules How many O atoms are contained in 100. mg of the acid? (a) 2.19 x 10 21 atoms (b) 4.47 x 10 19 atoms (c) 3.13 x 10 20 atoms (d) 6.02 x 10 23 atoms

Chapter 3 Compounds and Molecules Page 9 3-50. The compound HSCH 2 CHNH 2 COOH is the amino acid cysteine, a molecule crucial to life. (i) (ii) (iii) What is the weight percent of sulfur in the molecule? (a) 5.82% (b) 29.74% (c) 11.56% (d) 26.46% If you have 0.150 g of cysteine, how many moles of cysteine are present? (a) 1.24 x 10-3 mol (b) 6.20 x 10-4 mol (c) 2.48 x 10-3 mol (d) 806 mol How many H atoms are there in 0.150 g of cysteine? (a) 7.47 x 10 20 atoms (b) 6.02 x 10 23 atoms (c) 5.22 x 10 21 atoms (d) 2.09 x 10 22 atoms

Chapter 3 Compounds and Molecules Page 10 ANSWERS CHAPTER 3 1. c 11. c 21. a 2. a 12. b 22. d 3. b 13. c 23. c 4. a 14. b 24. b 5. d 15. c 25. a 6. b 16. a 26. b 7. c 17. d 27. d 8. i = c, ii = a, iii = d, iv = b 18. b 28. c 9. a 19. a 29. a 10. d 20. i = c, ii = d, iii = b, iv = a 30. b 31. d 41. d 32. c 42. c 33. a 43. c 34. c 44. d 35. a 45. d 36. b 46. d 37. c 47. b 38. a 48. d 39. b 49. i = a, ii = b, iii = a 40. d 50. i = d, ii = a, iii = c