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Formulas Name: ____________________________________ Tuesday, June 03, 2008 1. Given the incomplete equation: 2N 2O5(g) _____ Which set of products completes and balances the incomplete equation? 1. 2N2(g) + 3H2(g) 2. 2N2(g) + 2O2(g) 3. 4NO2(g) + O2(g) 4. 4NO(g) + 5O2(g) 2. Base your answer to the question on the information below. Ozone gas, O 3, can be used to kill adult insects in storage bins for grain without damaging the grain. The ozone is produced from oxygen gas, O2, in portable ozone generators located near the storage bins. The concentrations of ozone used are so low that they do not cause any environmental damage. This use of ozone is safer and more environmentally friendly than a method that used bromomethane, CH3Br. However, bromomethane was more effective than ozone because CH3Br killed immature insects as well as adult insects. Adapted From: The Sunday Gazette (Schenectady, NY) 3/9/03 Figure 1 Determine the total number of moles of CH3Br in 19 grams of CH3Br (gram-formula mass = 95 grams/mol). Answer: mol Formulas 3. Base your answer to the question on the information below. The particle diagrams below represent the reaction between two nonmetals, A2 and Q2 Figure 2 Using the symbols A and Q, the chemical formula of the product could be written as 1. AQ 3. AQ2 2. A2Q 4. A2Q2 4. Given the equation: If 8.0 moles of O2 are completely consumed, what is the total number of moles of H2O produced? mol Formulas 5. Which particle diagram represents one pure substance, only? 1. 3. 2. 4. 6. Given the reaction: CH4(g) + 2O2(g) CO2(g) + 2H2O(g) How many moles of oxygen are needed for the complete combustion of 3.0 moles of CH4(g)? 1. 6.0 moles 2. 2.0 moles 3. 3.0 moles 4. 4.0 moles 7. What is the molecular formula of a compound that has a molecular mass of 54 and the empirical formula C 2H3? 1. C2H3 2. C4H6 3. C6H9 4. C8H12 8. Given the balanced equation representing a reaction: What is the mole ratio of H 2(g) to HF(g) in this reaction? 1. 1:1 3. 2:1 2. 1:2 4. 2:3 Formulas 9. What is the gram formula mass of Li 2SO4? 1. 54g 2. 55g 3. 110g 4. 206g 10. What is the percent by mass of nitrogen in the compound NH 4NO3 (formula mass = 80.)? 1. 5.7% 2. 18% 3. 29% 4. 35% 11. Which substance represents a compound? 1. C(s) 2. Co(s) 3. CO(g) 4. O2(g) 12. Two alcohols that are used in our everyday lives are rubbing alcohol and ethylene glycol. Rubbing alcohol is used as an antiseptic. Ethylene glycol is the main ingredient in antifreeze, which is used in automobile cooling systems. Figure 3 What is the gram-formula mass of ethylene glycol, C 2H4(OH)2? g/mol 13. Which pair consists of a molecular formula and its corresponding empirical formula? 1. C2H2 and CH3CH3 3. P4O10 and P2O5 2. C6H6 and C2H2 4. SO2 and SO3 Formulas 14. Given the balanced equation: 2 C4H10(g) + 13 O2 (g) → 8 CO2 (g) + 10 H2 O(g) What is the total number of moles of O2 (g) that must react completely with 5.00 moles of C4H10(g )? 1. 10.0 2. 20.0 3. 26.5 4. 32.5 15. Which process represents a chemical change? 1. melting of ice 2. corrosion of copper 3. evaporation of water 4. crystallization of sugar 16. Given the reaction: 6 CO2 + 6 H2O → C2H12O6 + 6 O 2 What is the total number of moles of water needed to make 2.5 moles of C2H12O6? 1. 2.5 2. 6.0 3. 12 4. 15 17. Antacids can be used to neutralize excess stomach acid. Brand A antacid contains the acid neutralizing agent magnesium hydroxide, Mg(OH)2. It reacts with HCl(aq) in the stomach, according to the following balanced equation: If a person produces 0.050 mole of excess HCl in the stomach, how many moles of Mg(OH) 2 are needed to neutralize this excess hydrochloric acid? mole(s) Formulas 18. Given the equation: __Ca 2+ (aq) + __PO43- (aq) __Ca3(PO4)2(s) When the equation is correctly balanced, the sum of the total charge of the reactants is 1. 0 2. +2 3. -3 4. +6 19. What is the empirical formula of the compound whose molecular formula is P 4O10? 1. PO 2. PO2 3. P2O5 4. P8O20 20. Which pair of formulas correctly represents a molecular formula and its corresponding empirical formula? 1. C2H2 and CH 2. C3H4 and CH2 3. C4H6 and CH 4. C5H8 and C2H2 21. Which substance has the same molecular and empirical formulas? 1. C6H4 2. C2H4 3. CH4 4. C6H12O6 22. Given the reaction: 4NH 3 + 5O2 → 4NO + 6H2 O What is the total number of moles of NO produced when 1.0 mole of O2 is completely consumed? 1. 1.0 mole 2. 1.2 moles 3. 0.80 mole 4. 4.0 moles Formulas 23. Which two substances can not be broken down by chemical change? 1. C and CuO 3. CO2 and CuO 2. C and Cu 4. CO2 and Cu 24. Which statement describes a chemical property of oxygen? 1. Oxygen has a melting point of 55 K. 2. Oxygen can combine with a metal to produce a compound. 3. Oxygen gas is slightly soluble in water. 4. Oxygen gas can be compressed. 25. What is the correct IUPAC name for the compound NH 4Cl? 1. nitrogen chloride 2. nitrogen chlorate 3. ammonium chloride 4. ammonium chlorate 26. Element X reacts with iron to form two different compounds with the formulas FeX and Fe2X3. To which group on the Periodic Table does element X belong? 1. Group 8 3. Group 13 2. Group 2 4. Group 16 27. Which equation is correctly balanced? 1. H2 + O 2 → H2O 2. Ca + Cl2 → CaCl 3. 2H2 + O 2 → 2H2O 4. Ca + Cl2 → Ca2Cl Formulas 28. Which equation shows a conservation of mass? 1. Na + Cl2 → NaCl 3. H2O → H2 + O 2 2. Al + Br2→ AlBr3 4. PCl5 → PCl3 + Cl2 29. Which quantity is represented by the symbol He? 1. 1 gram of helium 2. 1 liter of helium 3. 1 mole of helium 4. 1 atomic mass unit of helium 30. An unknown element X can form a compound with the formula XBr3. In which group on the Periodic Table would element X be found? 1. 1 2. 2 3. 13 4. 14 31. What is the empirical formula of a compound with the molecular formula N 2O4? 1. NO 2. NO2 3. N2O 4. N2O3 32. A hydrate is a compound that includes water molecules within its crystal structure. During an experiment to determine the percent by mass of water in a hydrated crystal, a student found the mass of the hydrated crystal to be 4.10 grams. After heating to constant mass, the mass was 3.70 grams. What is the percent by mass of water in this crystal? 1. 90.% 2. 11% 3. 9.8% 4. 0.40% Formulas 33. Base your answer to the question on the particle diagrams below, which show atoms and/or molecules in three different samples of matter at STP. When two atoms of y react with one atom of z, a compound forms. Using the number of atoms shown in sample 2, what is the maximum number of molecules of this compound that can be formed? At most molecule(s) 34. Given the balanced equation: What is the total number of moles of CO2 formed when 20. moles of HCl is completely consumed? 1. 5.0 mol 3. 20. mol 2. 10. mol 4. 40. mol Formulas 35. Given the balanced equation: 4Al(s) + 3O 2(g) → 2Al2O3(s) What is the total number of moles of O2(g) that must react completely with 8.0 moles of Al(s) in order to form Al2O3 (s)? mol 36. In the 19th century, Dmitri Mendeleev predicted the existence of a then unknown element X with a mass of 68. He also predicted that an oxide of X would have the formula X2O3. On the modern Periodic Table, what is the group number and period number of element X? Group number: Period: 37. Which set of procedures and observations indicates a chemical change? 1. Ethanol is added to an empty beaker and the ethanol eventually disappears. 2. A solid is gently heated in a crucible and the solid slowly turns to liquid. 3. Large crystals are crushed with a mortar and pestle and become powder. 4. A cool, shiny metal is added to water in a beaker and rapid bubbling occurs. 38. Given the balanced equation representing a reaction: 4NH3 + 5O 2 4NO + 6H2O What is the minimum number of moles of O2 that are needed to completely react with 16 moles of NH3? 1. 16 mol 3. 64 mol 2. 20. mol 4. 80. mol Formulas 39. What is the total mass of oxygen in 1.00 mole of Al2(CrO4)3? 1. 192 g 2. 112 g 3. 64.0 g 4. 48.0 g 40. Base your answer to the question on the information below. Air bags are an important safety feature in modern automobiles. An air bag is inflated in milliseconds by the explosive decomposition of NaN3(s). The decomposition reaction produces N 2(g), as well as Na(s), according to the unbalanced equation below. NaN3(s) Na(s) + N2(g) Figure 4 Balance the equation for the decomposition of NaN 3, using the smallest whole-number coefficients. NaN3(s) Na(s) + N2(g) 41. Given the equation: 2C 2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g) How many moles of oxygen are required to react completely with 1.0 mole of C2H2? 1. 2.5 2. 2.0 3. 5.0 4. 10 42. A compound has a gram formula mass of 56 grams per mole. What is the molecular formula for this compound? 1. CH2 2. C2H4 3. C3H6 4. C4H8 Formulas 43. Which list consists of types of chemical formulas? 1. atoms, ions, molecules 2. metals, nonmetals, metalloids 3. empirical, molecular, structural 4. synthesis, decomposition, neutralization 44. What is the gram formula mass of Ca 3(PO4)2? 1. 135 g/mol 2. 215 g/mol 3. 278 g/mol 4. 310. g/mol 45. Base your answer to the question on the information below. In preparing to titrate an acid with a base, a student puts on goggles and an apron. The student uses burets to dispense and measure the acid and the base in the titration. In each of two trials, a 0.500 M NaOH(aq) solution is added to a flask containing a volume of HCl(aq) solution of unknown concentration. Phenolphthalein is the indicator used in the titration. The calculated volumes used for the two trials are recorded in the table below. Figure 5 Based on the information given in the table, how many significant figures should be shown in the calculated molarity of the HCl(aq) solution used in trial 2? Answer: significant figures Formulas 46. Which pair is classified as chemical substances? 1. mixtures and solutions 2. compounds and solutions 3. elements and mixtures 4. compounds and elements 47. What is the total number of moles of oxygen atoms present in one mole of Mg(ClO3)2? 1. 5 2. 2 3. 3 4. 6 48. The gram formula mass of NH 4Cl is 1. 22.4 g/mole 2. 28.0 g/mole 3. 53.5 g/mole 4. 95.5 g/mole 49. Given the balanced equation representing the reaction between propane and oxygen: C3H- + 5O 2 3CO2 + 4H2O According to this equation, which ratio of oxygen to propane is correct? 1. 2. 3. 4. Formulas 50. Which type of matter is composed of two or more different elements that are chemically combined in a definite ratio? 1. a solution 2. a compound 3. a homogeneous mixture 4. a heterogeneous mixture Formulas Answer Key for Formulas 1. 3 2. 0.20 3. 3 4. 16 5. 1 6. 1 7. 2 8. 2 9. 3 10. 4 11. 3 12. 62 13. 3 14. 4 15. 2 16. 4 17. 0.025 18. 1 19. 3 20. 1 21. 3 22. 3 23. 2 24. 2 25. 3 26. 4 27. 3 28. 4 29. 3 30. 3 31. 2 32. 3 33. 2 34. 2 35. 6 36. 13, 4 37. 4 38. 2 39. 1 40. 2, 2, 3 41. 1 42. 4 43. 3 44. 4 45. 3 46. 4 Formulas 47. 4 48. 3 49. 2 50. 2