## Chapter 6 Practice Questions

1) The chemical formula clearly indicates the relationship between the mass of each element in the formula. | false |

2) Mass is used as a method of counting atoms | true |

3) One hundred nickels must have the same mass as one hundred pennies. | false |

4) The numerical value of the mole is defined as being equal to the number of atoms in exactly 12 grams of pure carbon-12. | false |

5) The mole has a value of 6.023 × 1022 | false |

6) Avogadro’s Number is 6.022 × 1023. | true |

7) The number 6.022 × 1023 is six times larger than the number 6.022 × 1022. | false |

8) The lighter the atom, the less mass in one mole of that atom. | true |

9) One mole of argon has more atoms in it than one mole of neon. | false |

10) One mole of nitrogen gas contains (2) × (6.022 × 1023) nitrogen atoms. | true |

11) One mole of zinc contains 65.39 zinc atoms. | false |

12) One mole of copper atoms is 6.022 × 1023 copper atoms | true |

13) The mass of 2.0 moles of H2O is greater than the mass of 1.0 mole of CO2. | false |

15) Two moles of cobalt atoms have a mass of 117.87 grams | true |

16) Six grams of carbon contains 3.008 × 1023 atoms. | true |

17) One mole of I2 has more atoms in it than one mole of Na. | true |

18) One mole of CO2 gas contains 1 mole of carbon atoms and 2 moles of oxygen atoms. | true |

19) The molar mass of a compound in grams per mole is numerically equal to the formula mass of the compound in atomic mass units. | true |

20) One mole of water contains 16 grams of oxygen atoms. | true |

21) One mole of water contains 6.022 × 1023 hydrogen atoms | false |

22) There are 6 grams of carbon in 22 grams of carbon dioxide. | true |

23) The molar mass of a compound serves as a conversion factor between grams and moles. | true |

24) One mole of lead(II) nitrate contains six moles of oxygen atoms. | true |

25) The chemical formula CuBr2 indicates that this compound is composed of 1 gram of copper and 2 grams of bromine. | false |

26) The correct formula for calculating mass percent of X in compound XY is: MASS OF X/MASS OF Y = Mass % X | false |

27) Water is 11.2% hydrogen by mass. | true |

28) C2H3O2 could be an empirical formula. | true |

29) c2h6o3 could be an empirical formula. | true |

30) C2H6O4 could be an empirical formula. | false |

31) An empirical formula gives the specific number of each type of atom in a molecule. | false |

32) An empirical formula gives the smallest whole number ratio of each type of atom in a molecule. | true |

33) The empirical formula for C6H6 is c3h3. | false |

34) The molecular formula is equal to the empirical formula multiplied by a whole number integer | true |

35) A molecule that has an empirical formula of HO and a molar mass of 34.02 gram must have a molecular formula of H2O2. | true |

36) The empirical formula mass is 18.0 and the molecular formula mass is 90, therefore n = 5. | true |

37) The empirical formula mass must be 25.0 if the molecular formula mass is 250 and n = 5. | false |

1) What is the correct value for Avogadro’s number? A) 6.022 × 1023 B) 6.022 × 1033 C) 6.023 × 1022 D) 6.022 × 102.3 E) none of the above | A) 6.022 × 1023 |

2) One half of a mole of atoms would contain how many atoms? A) 0.5 B) 3.011 × 1023 C) 6.022 × 1023 D) 6.022 × 1011.5 E) none of the above | B) 3.011 × 1023 |

3) Which of the following statements about the mole is FALSE? A) One mole of atoms makes up an amount of atoms that can be seen with the naked eye. B) A mole of a monatomic element corresponds to one Avogadro’s number of atoms. C) One mole of a monatomic element has a mass equal to its atomic mass expressed in grams. D) One mole of water contains 1/2 mole of oxygen atoms. E) none of the above | D) One mole of water contains 1/2 mole of oxygen atoms. |

4) How many atoms are in 5.80 moles of He? A) 6.02 × 1023 B) 1.03 × 1023 C) 4.00 D) 3.49 × 1024 E) none of the above | D) 3.49 × 1024 |

5) How many atoms are in 1.50 moles of fluorine gas? A) 6.022 × 1023 B) 9.03 × 1023 C) 18.98 D) 1.81 × 1024 E) none of the above | D) 1.81 × 1024 |

6) How many moles of Cu are in 1.48 × 1025 Cu atoms? A) 0.0408 B) 24.6 C) 1.54 × 1025 D) 6.022 × 1023 E) none of the above | B) 24.6 |

7) One mole of boron has a mass of ________ g. A) 9.012 B) 6.022 × 1023 C) 5 D) 10.811 E) none of the above | D) 10.811 |

8) One mole of oxygen gas has a mass of ________ g. A) 16.0 B) 32.0 C) 6.022 × 1023 D) 8 E) none of the above | B) 32.0 |

9) What is the mass in grams of 5.40 moles of lithium? A) 6.94 B) 37.5 C) 1.29 D) 3.25 × 1024 E) none of the above | B) 37.5 |

10) What is the mass of 0.560 moles of chlorine gas? A) 19.9 B) 63.3 C) 127 D) 39.7 E) none of the above | D) 39.7 |

11) You have 10.0 g each of Na, C, Pb, Cu and Ne. Which contains the largest number of moles? A) Na B) C C) Pb D) Cu E) Ne | B) C |

12) You have 10.0 g each of Na, C, Pb, Cu and Ne. Which contains the smallest number of moles? A) Na B) C C) Pb D) Cu E) Ne | B) C |

13) How many moles of iron are contained in 1.75 kg of iron? A) 3.13 × 10-2 B) 3.13 × 10-4 C) 31.3 D) 3.13 × 104 E) none of the above | C) 31.3 |

14) How many moles are there in 17.5 grams of sodium? A) 22.99 B) 1.05 × 1025 C) 0.761 D) 1.31 E) none of the above | C) 0.761 |

15) How many moles are there in 82.5 grams of iron? A) 4.97 × 1025 B) 55.85 C) 0.677 D) 1.48 E) none of the above | D) 1.48 |

16) How many moles of bromine gas are in 37.7 grams? A) 0.236 B) 0.472 C) 3.01 × 103 D) 79.9 E) none of the above | A) 0.236 |

17) How many atoms are in 15.6 grams of silicon? A) 2.64 × 1026 B) 3.34 × 1023 C) 0.555 D) 438 E) none of the above | B) 3.34 × 1023 |

18) How many hydrogen atoms are in 35.0 grams of hydrogen gas? A) 4.25 × 1025 B) 2.09 × 1025 C) 2.12 × 1025 D) 1.05 × 1025 E) none of the above | D) 1.05 × 1025 |

19) What is the mass of 3.09 × 1024 atoms of sulfur in grams? A) 9.64 × 1022 B) 9.91 × 1025 C) 165 D) 0.160 E) none of the above | C) 165 |

20) How many moles of Pb are in 4.71 × 1021 Pb atoms? A) 0.00782 B) 2.84 × 1045 C) 207.2 D) 6.022 × 1023 E) none of the above | A) 0.00782 |

21) What is the mass of 1.56 × 1021 atoms of magnesium in grams? A) 4.72 × 10-5 B) 0.0630 C) 0.142 D) 1.07 × 10-4 E) none of the above | B) 0.0630 |

22) In comparing a balloon containing 25 grams of helium to a balloon containing 25 grams of neon, which one of the following statements is TRUE? A) Each balloon has an equal number of atoms. B) The helium balloon has more atoms. C) The neon balloon has more atoms. D) This scenario cannot happen because gases have no mass. E) none of the above | B) The helium balloon has more atoms. |

23) In comparing 1 mole of carbon atoms to one mole of magnesium atoms, which statement is TRUE? A) The mass of 1 mole of carbon is greater than the mass of 1 mole of magnesium. B) The mass of 1 mole of magnesium is greater than the mass of 1 mole of carbon. C) The mass of 1 mole of carbon is the same as the mass of 1 mole of magnesium. D) There are more atoms in 1 mole of magnesium than in 1 mole of carbon. E) none of the above | B) The mass of 1 mole of magnesium is greater than the mass of 1 mole of carbon. |

24) Which of the following contains 9.02 × 1023 atoms? A) 4.00 g H2 B) 9.00 g H2O C) 28.0 g N2 D) 32.0 g O2 E) none of the above | B) 9.00 g H2O |

25) The mass of one mole of carbon dioxide is ________ g. A) 28.01 B) 384.4 C) 32.00 D) 44.01 E) none of the above | D) 44.01 |

26) What is the molar mass of aluminum sulfate? A) 123.0 g/mol B) 278.0 g/mol C) 306.2 g/mol D) 315.2 g/mol E) 342.2 g/mol | E) 342.2 g/mol |

27) Calculate the molar mass of ammonium carbonate. A) 78.05 g/mol B) 88.05 g/mol C) 96.09 g/mol D) 112.09 g/mol E) none of the above | C) 96.09 g/mol |

28) Calculate the molar mass of calcium nitrate. A) 136.03 g/mol B) 102.09 g/mol C) 132.10 g/mol D) 164.10 g/mol E) none of the above | D) 164.10 g/mol |

29) How many molecules of sulfur trioxide are in 78.0 grams? A) 5.87 × 1023 B) 7.33 × 1023 C) 3.76 × 1027 D) 0.974 E) none of the above | A) 5.87 × 1023 |

30) How many molecules of nitrogen monoxide are in a 22.5 gram sample? A) 5.86 × 1023 B) 7.33 × 1023 C) 4.51 × 1023 D) 4.06 × 1023 E) none of the above | C) 4.51 × 1023 |

31) If 3.011 × 1023molecules have a mass of 20.04 grams, what is the molar mass of this substance? A) 40.08 g/mol B) 10.02 g/mol C) 20.04 g/mol D) 6.658 × 10-23g/mol E) none of the above | A) 40.08 g/mol |

32) If 2.01 × 1023 atoms of an element from Group IA of the periodic table has a mass of 7.675 grams, this element is most likely: A) Li. B) Na. C) K. D) Rb. E) Cs. | B) Na. |

33) One mole of (NH4)2HPO4 contains how many moles of hydrogen atoms? A) 4 B) 2 C) 8 D) 9 E) none of the above | D) 9 |

34) One mole of ammonium nitrate contains: A) 3 moles of hydrogen. B) 2 moles of oxygen. C) 2 moles of nitrogen. D) 1 mole of nitrogen. E) none of the above | C) 2 moles of nitrogen. |

35) One mole of ammonium nitrite contains: A) 2 moles of nitrogen atoms. B) 4 moles of hydrogen atoms. C) 2 moles of oxygen atoms. D) All of A, B, and C. E) None of A, B, and C. | D) All of A, B, and C. |

36) One mole of potassium sulfate contains: A) 4 moles of oxygen. B) 2 moles of sulfur. C) 1 mole of potassium. D) 3 moles of potassium. E) none of the above | A) 4 moles of oxygen. |

37) How many moles of carbon are in 3.5 moles of calcium carbonate? A) 10.5 B) 3.5 C) 7 D) 100.09 E) none of the above | B) 3.5 |

38) How many moles of fluorine are in 3.2 moles of xenon hexafluoride? A) 22.4 B) 12.8 C) 19.2 D) 16 E) none of the above | C) 19.2 |

39) If a sample of carbon dioxide contains 3.8 moles of oxygen atoms, how many moles of carbon dioxide are in the sample? A) 1.9 B) 3.8 C) 7.6 D) 11.4 E) none of the above | A) 1.9 |

40) A 15.5 gram sample of diphosphorous pentoxide contains how many grams of phosphorous? A) 3.38 B) 1.69 C) 6.76 D) 13.5 E) none of the above | C) 6.76 |

41) A 42.7 gram sample of potassium nitrate contains how many grams of potassium? A) 39.1 B) 16.5 C) 21.4 D) 8.54 E) none of the above | B) 16.5 |

42) An iron ore sample is found to be 35.00% Fe by mass. How many grams of ore are needed to obtain 454.0 grams of Fe? A) 1297 B) 158.9 C) 295.1 D) 350.0 E) none of the above | A) 1297 |

43) A 500. gram iron ore sample was determined to contain 242 grams of iron. What is the mass percent of iron in the ore? A) 93.7 B) 48.4 C) 51.6 D) 32.6 E) none of the above | B) 48.4 |

44) Bauxite is an ore that contains the element aluminum. If you obtained 108 grams of aluminum from an ore sample that initially weighed 204 grams, what is the mass percent of aluminum in this bauxite ore? A) 52.9 B) 15.6 C) 0.53 D) 47.1 E) none of the above | A) 52.9 |

45) What is the mass percent of hydrogen in water? A) 33.3 B) 88.8 C) 5.60 D) 11.2 E) none of the above | D) 11.2 |

46) What is the mass percent of chlorine in hydrochloric acid? A) 2.8 B) 35.5 C) 97.2 D) 70.1 E) none of the above | C) 97.2 |

47) What is the mass percent of carbon in oxalic acid, H2C2O4? A) 2.24 B) 13.3 C) 26.7 D) 34.5 E) none of the above | C) 26.7 |

48) Which of the following compounds has the highest mass percent of “O”? A) MnO B) MnO2 C) Mn2O3 D) Mn3O2 E) none of the above | B) MnO2 |

49) Which of the following statements about empirical formulas is incorrect? A) An empirical formula represents a molecule. B) An empirical formula gives the smallest whole number ratio of each type of atom in a molecule. C) An empirical formula must be multiplied by an integer to obtain the molecular formula. D) The molecular formula can be the same as the empirical formula in some situations. E) All statements are correct. | A) An empirical formula represents a molecule. |

50) The empirical formula of a compound: A) describes the mass relationships in a molecule. B) is the same as the molecular formula. C) indicates the structure of the molecule. D) indicates the simplest ratio of atoms in the compound. E) none of the above | D) indicates the simplest ratio of atoms in the compound. |

51) The simplest formula for hydrogen peroxide is HO. To determine its molecular formula, it is necessary to know: A) the properties of hydrogen peroxide. B) the density of hydrogen peroxide. C) the molar mass of hydrogen peroxide. D) the number of moles of hydrogen peroxide in 1.00 g of the substance. E) none of the above | C) the molar mass of hydrogen peroxide. |

52) Which of the following is already in its empirical formula? A) C22H34O10 B) C6H6 C) c6h12o3-structure/”>c6h12o3 D) C5H12O2 E) none of the above | D) C5H12O2 |

53) The chemical formula CH2O can be classified as: A) molecular only. B) empirical only. C) empirical, possibly molecular. D) not enough information E) none of the above | C) empirical, possibly molecular. |

54) A chromium oxide compound contains 104.0 grams of chromium and 48.0 grams of oxygen. What is the most likely empirical formula of this compound? A) CrO B) CrO2 C) CrO3 D) Cr2O3 E) Cr3O2 | D) Cr2O3 |

55) An iron chloride compound contains 55.85 grams of iron and 106.5 grams of chlorine. What is the most likely empirical formula for this compound? A) FeCl B) FeCl2 C) Fe2Cl D) FeCl3 E) Fe3Cl | D) FeCl3 |

56) A 7.96 gram sample of silver reacts with oxygen to form 8.55 gram of the metal oxide. What is the formula of the oxide? A) AgO B) AgO2 C) Ag2O D) Ag3O E) none of the above | C) Ag2O |

57) Determine the empirical formula of a compound containing 60.3% magnesium and 39.7% oxygen. A) MgO B) MgO2 C) Mg2O3 D) Mg2O E) none of the above | A) MgO |

58) Determine the empirical formula of a compound containing 83% potassium and 17.0% oxygen. A) KO B) KO2 C) K2O3 D) K2O E) none of the above | D) K2O |

59) Vitamin C is known chemically by the name ascorbic acid. Determine the empirical formula of ascorbic acid if it is composed of 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen. A) CHO B) CH2O C) C2H3O2 D) c3h4o3 E) none of the above | D) C3H4O3 |

60) Determine the correct empirical formula of a compound containing 26.68% carbon, 2.24% hydrogen, and 71.08% oxygen. A) CHO B) CHO2 C) C0.5H0.5O1 D) c2h2o4 E) none of the above | B) CHO2 |

61) A compound composed of only carbon and hydrogen is 25.2% hydrogen by mass. The empirical formula for this compound is: A) CH 0.25 B) C3H C) CH4 D) C2H8 E) none of the above | C) CH4 |

62) What is the molecular formula of a compound given the molar mass of the compound is 186.5 gram and the empirical formula is C2H7? A) C4H14 B) C3H21 C) C2H7 D) C2H14 E) none of the above | E) none of the above |

63) An estrogen compound with the empirical formula C12H17O2 has a molecular mass of 386.6 g/mol. What is the value of n necessary to find the molecular formula? A) 0.2 B) 1 C) 2 D) 20 E) none of the above | C) 2 |

64) What is the value of n when the empirical formula is C3H5 and the molecular mass is 205.4 g/mol? A) 0.02 B) 5 C) 10 D) 140 E) none of the above | B) 5 |

65) What would the empirical formula be for the molecular compound c6h9O4? A) C2H3O2 B) CH3O2 C) C3H6O2 D) C3H9O4 E) none of the above | E) none of the above |

66) What is the molecular formula of a compound given the molar mass of the compound is 30.04 gram and the empirical formula is NH? A) NH B) N2H2 C) N2H6 D) N4H4 E) none of the above | B) N2H2 |

67) A compound has a molar mass of 180.18 g/mol. Given the following percent composition, calculate the molecular formula: 39.99% C, 6.73% H, 53.28% O. A) CH3O2 B) CH2O C) C3H6O3 D) C6H12O6 E) none of the above | D) C6H12O6 |

68) An unknown acid has a molar mass of 60.06 g/mol. Given the following percent composition, what is the molecular formula? 40% C, 6.7% H, 53.3% O . A) C3H4O3 B) CH2O C) C2H4O2 D) C6H12O6 E) none of the above | C) C2H4O2 |

69) A compound composed of only hydrogen and oxygen is 5.94% hydrogen by mass. The molar mass of this compound is 34.02 g/mol. What is the compound’s molecular formula? A) 34.02 B) H2O2 C) HO D) H6O E) none of the above | B) H2O2 |

1) Bananas cost 33¢ per pound. If you spent $0.77, how many pounds of bananas did you purchase? A) 2.33 B) 1.73 C) 0.429 D) 2.01 E) none of the above | A) 2.33 |

2) How many atoms are present in 4.5 moles? A) 3.7 x 1023 B) 3.7 x 10-25 C) 2.7 x 1024 D) 6.02 x 1023 E) none of the above | C) 2.7 x 1024 |

3) If you have 2.41 x 1024 atoms of copper, how many moles of copper do you have? A) 0.250 B) 4.00 C) 0.600 D) 3.00 E) none of the above | B) 4.00 |

4) How many moles of potassium are in 156.4 g? A) 39.10 B) 4.000 C) 0.2500 D) 5.050 E) none of the above | B) 4.000 |

5) What is the mass of 3.91 x 1024 sulfur atoms? A) 208 B) 4.93 C) 155 D) 32.07 E) none of the above | A) 208 |

6) How many atoms of lithium are in 18.7 g? A) 2.14 x 1024 B) 2.70 x 1024 C) 1.62 x 1024 D) 3.11 x 1024 E) none of the above | C) 1.62 x 1024 |

7) What is the mass (in grams) of 1.95 moles of water ? A) 18.02 B) 9.24 C) 35.1 D) 6.022 × 10 23 E) none of the above | C) 35.1 |

8) What is the mass (in grams) of 3.03 × 1024 molecules of carbon dioxide molecules? A) 221 B) 0.114 C) 1.33 D) 44.01 E) none of the above | A) 221 |

9) How many moles of oxygen are in 3.30 moles of NaClO4 ? A) 3.30 B) 0.303 C) 19.0 D) 13.2 E) none of the above | D) 13.2 |

10) Given that sodium chloride is 39.0% sodium by mass, how many grams of sodium chloride are needed to have 950 mg of Na present? A) 2.44 B) 0.371 C) 2,430 D) 37.1 E) none of the above | A) 2.44 |

11) What is the mass percent of Na in sodium chloride? A) 58.4 B) 60.7 C) 39.3 D) 47.5 E) none of the above | C) 39.3 |

12) What is the mass percent of oxygen in sodium oxide? A) 37.1 B) 25.8 C) 74.2 D) 62.0 E) none of the above | B) 25.8 |