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1 Mg, 2 O, and 2 H 2 Mg, 2 O, and 2 H 6 Mg, 6 O, and 6 H 3 Mg, 6 O, and 6 H

1 Mg, 2 O, and 2 H 2 Mg, 2 O, and 2 H 6 Mg, 6 O, and 6 H 3 Mg, 6 O, and 6 H. 1 Mg, 2 O, and 2 H 2 Mg, 2 O, and 2 H 6 Mg, 6 O, and 6 H 3 Mg, 6 O, and 6 H.   NaS   NaS 2   Na 2 S    Na 2 S 2.   NaS   NaS 2   Na 2 S    Na 2 S 2.

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1 Mg, 2 O, and 2 H 2 Mg, 2 O, and 2 H 6 Mg, 6 O, and 6 H 3 Mg, 6 O, and 6 H

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  1. 1 Mg, 2 O, and 2 H • 2 Mg, 2 O, and 2 H • 6 Mg, 6 O, and 6 H • 3 Mg, 6 O, and 6 H

  2. 1 Mg, 2 O, and 2 H • 2 Mg, 2 O, and 2 H • 6 Mg, 6 O, and 6 H • 3 Mg, 6 O, and 6 H

  3.   NaS •   NaS2 •   Na2S  •   Na2S2

  4.   NaS •   NaS2 •   Na2S  •   Na2S2

  5.  too few significant figures are used in the problem’s calculations. • there are experimental uncertainties in the measurements. •  coefficients are always rounded to integers so it doesn’t matter. •  approximations were made in the calculations.

  6.  too few significant figures are used in the problem’s calculations. • there are experimental uncertainties in the measurements. •  coefficients are always rounded to integers so it doesn’t matter. •  approximations were made in the calculations.

  7. 1.57 mol H2 reacts. • 0.785 mol H2 reacts. • Cannot be determined without more information. • 3.14 mol H2 reacts.

  8. 1.57 mol H2 reacts. • 0.785 mol H2 reacts. • Cannot be determined without more information. • 3.14 mol H2 reacts.

  9. The following equation is unbalanced: CS2+O2CO2+ SO2 What is the correct balanced equation? CS2 +2 O2→CO2+2 SO2 2 CS2 + 12 O2→2 CO2 + 4 SO2 CS2 + 3 O2→CO2 + 2 SO2 CS2 + 6 O2→CO2 + 2 SO2

  10. Correct Answer: CS2 +2 O2→CO2+2 SO2 2 CS2 + 12 O2→2 CO2 + 4 SO2 CS2 + 3 O2→CO2 + 2 SO2 CS2 + 6 O2→CO2 + 2 SO2 This is the only case where the number of each type of atom is the same on both the reactant and product sides of the equation.

  11. C C O Which of the following is the correct, balanced chemical equation for the combustion of ethanol (C2H5OH)? C2H5OH + O2→CO2+ H2O C2H5OH + 3 O2→2 CO2 + 3 H2O C2H5OH + 6 O2→4 CO2 + 6 H2O 2 C2H5OH + 7 O2→ 4 CO2 + 6 H2O O O

  12. C C O Correct Answer: C2H5OH + O2→CO2+ H2O C2H5OH + 3 O2→2 CO2 + 3 H2O C2H5OH + 6 O2→4 CO2 + 6 H2O 2 C2H5OH + 7 O2→ 4 CO2 + 6 H2O O O O

  13. If the empirical formula of a compound is C2H2N but the molecular weight is 160 g/mol, what is the molecular formula? C2H2N C4H4N2 C6H8N3 C8H8N4 None of the above choices is correct.

  14. Correct Answer: C2H2N C4H4N2 C6H8N3 C8H8N4 None of the above choices is correct. FWC2H2N = (24 + 2 + 14) g/mol = 40 g/mol MW/FW = 160/40 = 4 Thus, molecular formula is 4 empirical formula 4(C2H2N) = C8H8N4

  15. How many fluorine atoms are present in 2.0 moles of AlF3? 3.0  1023 6.0  1023 1.2  1024 3.6  1024 None of the above answers is correct.

  16. Correct Answer: 3.0  1023 6.0  1023 1.2  1024 3.6  1024 None of the above answers is correct. (2.0 moles AlF3)(6.0  1023 molecules AlF3/mole AlF3) (3 atoms F/1 molecule AlF3) = 3.6  1024

  17. Which of the following samples has the largest number of atoms? 28 g Si 28 g CO 28 g N2 15 g C2H4 All of the above have equal numbers of atoms.

  18. Correct Answer: 28 g Si 28 g CO 28 g N2 15 g C2H4 All of the above have equal numbers of atoms. 28 g Si has 1 mole of atoms, whereas 28 g of CO and N2 have 2 moles of atoms, even though they also have only 1 mole substance. However, there are 6 atoms for every 1 mole of C2H4, so in this case there are slightly more than 3 moles worth of atoms.

  19. The molecular mass for the compound, XClO3, is 122.5 amu. The atomic mass of X is equal to ____ amu, which is the element ____. 1.0; H 6.9; Li 23.0; Na 39.1; K 85.5; Rb

  20. Correct Answer: 1.0; H 6.9; Li 23.0; Na 39.1; K 85.5; Rb MW = 122.5 amu = AW X + AW Cl + 3(AW O) 122.5 amu AW Cl 3 (AW O) = AW X 122.5 amu (35.45 amu)  3 (16.0 amu) = AW X 122.5  35.45 amu 48.0 amu = AW X AW X = 39.1 amu

  21. When the chemical equation, C4H10(g) + O2(g) H2O(g) + CO2(g), is balanced, the stoichiometric coefficients are, respectively: 1, 4, 5, 4 2, 13, 10, 8 2, 9, 8, 10 2, 7, 4, 5

  22. Correct Answer: 1, 4, 5, 4 2, 13, 10, 8 2, 9, 8, 10 2, 7, 4, 5

  23. The combustion of methane (CH4) is shown below: CH4(g) + 2 O2(g) 2 H2O(l) + CO2(g) How many grams of water are produced in the combustion of 1.0 moles of methane? 16 g 32 g 36 g 48 g

  24. Correct Answer: 16 g 32 g 36 g 48 g (1.0 mole CH4)(2 moles H2O/1 mole CH4)(18 g H2O/1 mole H2O) = 36 g

  25. 0.5 mol of carbon is combusted with 1.0 mol of oxygen gas. Which of the following statements is correct? There is a molar excess of carbon, not all carbon is consumed. There is a molar excess of oxygen, not all oxygen is consumed. There are stoichiometrically equivalent amounts of carbon and oxygen gas.

  26. Correct Answer: There is a molar excess of carbon, not all carbon is consumed. There is a molar excess of oxygen, not all oxygen is consumed. There are stoichiometrically equivalent amounts of carbon and oxygen gas. C and O2 react in a 1:1 stoichiometric ratio, therefore there must be excess O2 because there was a larger initial number of moles of it.

  27. 0.5 mol of carbon is combusted with 1.0 mol g of oxygen gas. How many moles of carbon dioxide are produced? 1.5 mol 1.0 mol 0.5 mol 2.0 mol

  28. Correct Answer: 1.5 mol 1.0 mol 0.5 mol 2.0 mol C and O2 react in a 1:1 stoichiometric ratio, therefore C must be the limiting reagent and O2 must be the excess reagent. Initially, (0.5 moles C)(1 mole CO2/1 mole C) = 0.5 mole CO2

  29. 24.0 g of carbon are combusted with 32.0 g of oxygen gas. How many grams of carbon dioxide are produced? 56.0 g 88.0 g 28.0 g 44.0 g

  30. Correct Answer: 56.0 g 88.0 g 28.0 g 44.0 g C and O2 react in a 1:1 stoichiometric ratio. Initially, (24.0 g C)  (1 mole C/12.0 g C)  (1 mole CO2/1 mole C) = 2.0 mole CO2 (32.0 g O2)  (1 mole O2/32.0 g O2)  (1 mole CO2/1 mole O2) = 1.0 mole CO2 Thus, O2 is limiting, and 1.0 mole of CO2 is 44.0 g.

  31. 3.0 moles Mg are combusted with 2.0 moles O2. What is the limiting reagent and how many moles of the excess reagent remain? Magnesium, 0.5 mole Magnesium, 1.0 mole Oxygen gas, 0.5 mole Oxygen gas, 1.0 mole

  32. Correct Answer: Magnesium, 0.5 mole Magnesium, 1.0 mole Oxygen gas, 0.5 mole Oxygen gas, 1.0 mole Mg and O2 react in a 2:1 stoichiometric ratio. Initially, (3 mole Mg)(2 mole MgO/2 mole Mg) = 1.5 mole MgO (2 mole O2)(2 mole MgO/1 mole O2) = 4 mole MgO Thus, Mg is limiting, and 3 mol Mg will consume 1.5 mol of O2, leaving 0.5 mole of O2.

  33. How many oxygen atoms are presentin MgSO4 • 7 H2O? • 4 oxygen atoms • 5 oxygen atoms • 7 oxygen atoms • 11 oxygen atoms • 18 oxygen atoms

  34. How many oxygen atoms are presentin MgSO4 • 7 H2O? • 4 oxygen atoms • 5 oxygen atoms • 7 oxygen atoms • 11 oxygen atoms • 18 oxygen atoms

  35. How many sulfur atoms are presentin 1.0 mole of Al2(SO4)3? • 1 sulfur atom • 3 sulfur atoms • 4 sulfur atoms • 6.0 x 1023 sulfur atoms • 1.8 x 1024 sulfur atoms

  36. How many sulfur atoms are presentin 1.0 mole of Al2(SO4)3? • 1 sulfur atom • 3 sulfur atoms • 4 sulfur atoms • 6.0 x 1023 sulfur atoms • 1.8 x 1024 sulfur atoms

  37. An alkali metal Ca in H2O If you have equal masses of the following metals, which will have the most number of atoms? • Lithium • Sodium • Potassium • Rubidium • Calcium

  38. An alkali metal Ca in H2O If you have equal masses of the following metals, which will have the most number of atoms? • Lithium • Sodium • Potassium • Rubidium • Calcium

  39. 2 NO (g) + O2 (g) 2 NO2 (g) How many moles of oxygen gas are required to react completely with 1.0 mole NO? • 0.5 mol O2 • 1.0 mol O2 • 1.5 mol O2 • 2.0 mol O2 • 2.5 mol O2

  40. 2 NO (g) + O2 (g) 2 NO2 (g) How many moles of oxygen gas are required to react completely with 1.0 mole NO? • 0.5 mol O2 • 1.0 mol O2 • 1.5 mol O2 • 2.0 mol O2 • 2.5 mol O2

  41. 2 NO (g) + O2 (g) 2 NO2 (g) If 10.0 moles of NO are reacted with 6.0 moles O2, how many moles NO2 are produced? • 2.0 mol NO2 • 6.0 mol NO2 • 10.0 mol NO2 • 16.0 mol NO2 • 32.0 mol NO2

  42. 2 NO (g) + O2 (g) 2 NO2 (g) If 10.0 moles of NO are reacted with 6.0 moles O2, how many moles NO2 are produced? • 2.0 mol NO2 • 6.0 mol NO2 • 10.0 mol NO2 • 16.0 mol NO2 • 32.0 mol NO2

  43. If you have equal concentrations of the following aqueous solutions, which will have the highest conductivity? • CaCl2 • KBr • Na2SO4 • Al(NO3)3 • LiC2H3O2

  44. If you have equal concentrations of the following aqueous solutions, which will have the highest conductivity? • CaCl2 • KBr • Na2SO4 • Al(NO3)3 • LiC2H3O2

  45. NH + HF 3 HClO + KOH 4 Na SO + PbCl 2 4 2 Ca(NO ) + KC H O 3 2 2 3 2 (NH ) CO + Na PO 4 2 3 3 4 Which mixture will produce a precipitate?

  46. NH + HF 3 HClO + KOH 4 Na +PbCl SO 2 4 2 Ca(NO ) + KC H O 3 2 2 3 2 (NH ) CO + Na PO 4 2 3 3 4 Which mixture will produce a precipitate?

  47. KOH (aq) + HF (aq) KF (aq) + H2O (l) What is(are) the spectator ion(s) in the following reaction? • K+ • F- • K+ and F- • OH- and H+ • OH-

  48. KOH (aq) + HF (aq) KF (aq) + H2O (l) What is(are) the spectator ion(s) in the following reaction? • K+ • F- • K+ and F- • OH- and H+ • OH-

  49. H+(aq) + OH-(aq) H2O (l) Which of the following reactions has the net ionic equation: • Reaction 1 • Reactions 1, 4 • Reactions 2, 3 • Reactions 2, 4 • Reactions 3, 4

  50. H+(aq) + OH-(aq) H2O (l) Which of the following reactions has the net ionic equation: • Reaction 1 • Reactions 1, 4 • Reactions 2, 3 • Reactions 2, 4 • Reactions 3, 4

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