Stoichiometry A. N 2 H 4 +N 2 O 4! N 2 +H 2 O. 6. NH 3 (g) + O 2 (g)! N 2 (g) + H 2 O(g) CH 4 + 2O 2! CO 2 + 2H 2 O

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1 Name: ate: 1. Element and element chemically combine to form substance. Substance must be. a solution. a compound. an element. a mixture 5. Hydrazine, N 2 H 4, and dinitrogen tetroxide, N 2 O 4, react to form gaseous nitrogen and water. Which of these represents a properly balanced equation for this reaction?. N 2 H 4 +N 2 O 4! N 2 +H 2 O. 2N 2 H 4 +N 2 O 4! 2N 2 + 4H 2 O. 2N 2 H 4 +N 2 O 4! 3N 2 + 4H 2 O 2. Which substance can be decomposed by a chemical change?. 2N 2 H 4 + 3N 2 O 4! 5N 2 + 6H 2 O. ammonia. argon. iron. helium 3. The following equations represent chemical reactions. 6. NH 3 (g) + O 2 (g)! N 2 (g) + H 2 O(g) When the reaction above is completely balanced, the coe cient for NH 3 will be Which equation shows that the total mass during a chemical reaction stays the same? When methane (H 4 ) gas is burned in the presence of oxygen, the following chemical reaction occurs. H 4 + 2O 2! O 2 + 2H 2 O If 1 mole of methane reacts with 2 moles of oxygen, then molecules of O 2 and H 8 +O 2! O 2 +H 2 O This chemical equation represents the combustion of propane. When correctly balanced, the coe cient for water is molecules of O 2 and molecules of O 2 and molecules of O 2 and page 1

2 8. In the reaction of solid zinc with hydrochloric acid (Hl), the products of hydrogen gas and aqueous zinc chloride are produced. Which of these is the balanced equation from the reaction? 10. The law of conservation of mass can be demonstrated by a chemical reaction. Which of the following models of a chemical reaction best represents the law of conservation of mass?.. Zn(s) + Hl(aq)! Znl 2 (aq) + H(g). 2Zn(s) + 4Hl(aq)! Zn2l 4 (aq) + H 2 (g). Zn(s) + 2Hl(aq)! Znl 2 (aq) + H 2 (g).. Zn 2 (s) + Hl(aq)! 2Znl(aq) + H 2 (g).. 9. The tires on most cars are not made of natural rubber because it becomes brittle in the cold and sticky in the heat. Instead, natural rubber is vulcanized by adding sulfur and heat, making it stronger and more elastic. This process is represented chemically in the diagram below. The complete combustion or burning of natural rubber will produce.. hydrogen and oxygen. oxygen and water. hydrogen gas and water. carbon dioxide and water. page 2

3 11. Students in a biology laboratory are monitoring the rate at which hydrogen peroxide breaks down to produce water and oxygen gas. They begin monitoring a sample of hydrogen peroxide and then add catalase, an enzyme that speeds up its breakdown. Their data are shown in the table below. Time (min) Rate of Hydrogen Peroxide reakdown (molecules per min) ,970, ,001, ,985, ,021,700 ased on the data in this table, during which of the following time periods did the students add the catalase to the hydrogen peroxide?. between 0.0 and 0.5 min. between 1.0 and 1.5 min. between 2.0 and 2.5 min. between 2.5 and 3.0 min 13. n unbalanced chemical equation is shown below. Pb(NO 3 ) 2 + K2rO4! PbrO 4 + KNO 3 Which coe cients are needed to balance this equation?. 2, 4, 4, 6. 2, 4, 4, 3. 1, 1, 1, 2. 1, 6, 6, Potassium carbonate (K 2 O 3 ) is an important component of fertilizer. The partially balanced equation for the reaction of 6 moles of potassium hydroxide (KOH) and 3 moles of carbon dioxide (O 2 ) to produce potassium carbonate and water is given below. 6KOH + 3O 2! K 2 O 3 + 3H 2 O When this equation is balanced, what is the coe cient for potassium carbonate? opper in the compound uso 4 can be isolated in the following reaction with iron. Fe + uso 4! FeSO 4 + u What type of reaction is shown above?. decomposition. synthesis. single displacement. double displacement 15. luminum reacts vigorously and exothermically with copper(ii) chloride. Which of the following is the balanced equation for this reaction?. l + ul 2! ll 3 + u. l + 3ul 2! 2ll 3 + u. 2l + 3ul 2! 2ll 3 + 3u. 3l + 2ul 2! 3ll 3 + 2u page 3

4 16. Which of the following represents a double displacement reaction?.! +. +!. +! utane ( 4 H 10 ) is used as the fuel in many portable lighters. When butane is completely combusted in oxygen, what is the coe cient for the water produced in the properly balanced equation that represents the reaction? ! Which pair of formulas represents the empirical formula and the molecular formula of a compound? 17. Which of the following chemical reactions is a decomposition reaction?. H 2 O, 4 H 6 O 4. HO, 6 H 12 O 6. H 4, 5 H 12. H 2, 3 H 6. ao 3! ao + O 2. 2a + O 2! 2aO. 3r 2 + 2FeI 3.2Fer 3 + 3I 2. Mgl 2 +H 2 SO 4.MgSO 4 + 2Hl 21. compound contains 40% calcium, 12% carbon, and 48% oxygen by mass. What is the empirical formula of this compound?. ao 3. a 2 O The figure below represents a reaction.. a 3 O 6. ao Which formulas could represent the empirical formula and the molecular formula of a given compound?. H 2 O, 4 H 6 O 4. HO, 6 H 12 O 6 What type of reaction is shown?. H 4, 5 H 12. H 2, 3 H 6. synthesis. decomposition. single displacement. double displacement 23. compound has an empirical formula of H 2 and a molecular mass of 56. Its molecular formula is. 2 H 4. 3 H 6. 4 H 8. 5 H 10 page 4

5 24. What is the molecular formula of a compound with an empirical formula of H and a molecular mass of 78?. 6 H 6. 4 H H 2. H 25. The percent by mass of nitrogen in Mg(N) 2 is equal to 28. The accompanying table shows the data collected during the heating of a 10.0-gram sample of a hydrated salt. Heating Time (min) Mass of Salt (g) What is the percent of water in the original sample? %. 20%. 60%. 80% 26. What is the empirical formula of a compound whose composition by mass is 40% sulfur and 60% oxygen?. SO 2. SO 3. S 2 O 3. S 2 O sample of a substance containing only magnesium and chlorine was tested in the laboratory and was found to be composed of 74.5% chlorine by mass. If the total mass of the sample was grams, what was the mass of the magnesium? g g g. 142 g 30. Given the reaction: 27. compound consists of 46.7% nitrogen and 53.3% oxygen by mass. What is its empirical formula?. NO. NO 2. N 2 O. N 2 O 3 a + 2H 2 O! a(oh) 2 +H 2. How many moles of H 2 O are needed to exactly react with 2.0 moles of a? page 5

6 31. Given the equation: Zn + 2Hl! Znl 2 +H 2 How many moles of Hl would be required to produce a total of 2 moles of H 2? 33. Given the reaction: Mg + 2Hl! Mgl 2 +H 2 What is the total number of grams of Mg consumed when 0.50 mole of H 2 is produced? g. 12 g. 3.0 g. 24 g 32. Given the equation: 2 4 H O 2! 8O H 2 O How many moles of carbon dioxide are produced for each mole of butane consumed? Given the balanced equation representing a reaction: 2H 2 +O 2! 2H 2 O What is the total mass of water formed when 8 grams of hydrogen reacts completely with 64 grams of oxygen?. 18 g. 36 g. 56 g. 72 g page 6

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