AP Chapter 1, 2, & 3: Atoms, Molecules, and Mass Relationships Name

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1 AP Chapter 1, 2, & 3: Atoms, Molecules, and Mass Relationships Name Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

2 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 2 Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

3 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 3 Warm-ups and problems will be collected before you take the test. Read Chapters 1, 2, 3 Know the metric prefixes in Table 1.3 Know the cation and anion names in Table 2.3 Answer the following problems in the space provided. For problems involving an equation, carry out the following steps: 1. Write the equation. 2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work. Classification and Properties of Matter 1. How does an intensive property differ from an extensive property? Which of the following properties are intensive (I) and which are extensive (E)? (a) length (b) volume (c) temperature (d) mass. 2. Does each of the following describe a physical change (P) or a chemical change (C)? Explain. (a) The helium gas inside a balloon tends to leak out after a few hours. (b) A flashlight beam slowly gets dimmer and finally goes out. (c) Frozen orange juice is reconstituted by adding water to it. (d) The growth of plants depends on the sun's energy in a process called photosynthesis. (e) A spoonful of table salt dissolves in a bowl of soup. (f) Water is boiled. 3. Classify each of the following as an element (E), a compound (C), a homogeneous mixture (HOM), or a heterogeneous mixture (HET). (a) seawater (b) helium gas (c) sodium chloride (d) a bottle of soft drink (e) a milkshake (f) air (g) concrete. Measurements 4. What units do chemists normally use for density of liquids and solids? For gas density? Explain the difference? 5. The temperature on the surface of the sun is about 6300 C. What is this temperature in Kelvins? Numbers 6. Express the following numbers as decimals. (a) 1.52 x 10-2 (b) 7.78 x 10-8

4 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 4 7. How many significant figures are there in each of the following? (a) L (b) dm (c) cm 2 (d) 960 X 10-3 g (e) 60 people Dimensional Analysis (Conversion Factors) 8. For a fighter jet to take off from the deck of an aircraft carrier, it must reach a speed of 62 m/s. Calculate the speed in km/hr. 9. Vanillin (used to flavor vanilla ice cream and other foods) is the substance whose aroma the human nose detects in the smallest amount. The threshold limit is 2.0 x g per liter of air. If the current price of 50 g of vanillin is $112, determine the cost to supply enough vanillin so that the aroma could be detected in a large aircraft hangar with a volume of 1.4 x 10 9 L. (Hint: write the two conversion factors given in the problem.) 10. The total volume of seawater in all the world s oceans is 1.5 x L. Assume that seawater contains 3.1 percent sodium chloride by mass and that its density is 1.03 g/ml. Calculate the total mass of sodium chloride in kilograms. 11. A sheet of aluminum foil has a total area of 929 cm 2 and a mass of g. What is the thickness of the foil in millimeters? (Density of Al = g/cm 3.) 12. Chlorine is used to disinfect swimming pools. The accepted concentration for this purpose is 1 ppm chlorine, or one gram of chlorine per million grams of water. Calculate the volume of a chlorine solution (in milliliters) a homeowner should add to her swimming pool if the solution contains 6.0% chlorine by mass and there are 7.6 x 10 4 liters of water in the pool. (assume the density of liquids = 1.0 g/ml.)

5 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 5 Structure of the Atom 13. Roughly speaking, the radius of an atom is about 10,000 times greater than that of its nucleus. If an atom were magnified so that the radius of its nucleus became 2.0 cm, about the size of a marble, what would be the radius of the atom in kilometers? 14. Explain the meaning of each term in the symbol N A Z 15. Indicate the number of protons, neutrons, and electrons in each of the following species: (a) N (b) 16 S (c) 56 Ba 16. Give the number of protons and electrons in each of the following common ions: (a.) K + (b) Mg 2+ (c) Fe 3+ (d) Br - (e) C 4- Names and Formulas 17. What are the empirical formulas of the following compounds? (a) Al 2Br 6, (b) Na 2S 2O 4, (c) N 2O 5, (d) K 2Cr 2O Which of the following compounds are likely to be ionic (I)? Which are likely to be molecular (M)? (a). SiCl 4 (b). LiF (c). BaCl 2, (d). B 2H 6, (e). C 2H In which one of the following pairs do the two species resemble each other most closely in chemical properties? Explain. (a) H and 12 6 and C 1 H 1 (b) N and 7 N (c). C One isotope of a nonmetallic element has mass number 127 and 74 neutrons in the nucleus. The anion derived from the isotope has 54 electrons. Write the symbol for this anion. 21. Which of the following are elements (E), which are molecules (M) but not compounds (C), which are compounds but not molecules, and which are both compounds and molecules? (a) KBr (b) S 8 (c) S (d) N 2O 5 (e) O (f) O 3

6 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 6 Atomic Mass 22. Calculate the atomic mass of zirconium, given the following mass spectrum. 23. The atomic masses of Li-6 and Li-7 are amu and amu, respectively. Calculate the natural abundances of these two isotopes. The average atomic mass of Li is amu. 24. Earth's population is about 6.0 billion. Suppose that every person on Earth participates in a process-of counting identical particles at the rate of two particles per second. How many years would it take to count Avogadro s number of particles? 25. What is the mass in grams of a single atom of each of the following elements? (a) As (b) Ni. 26. The maximum density of water is 1.00 g/ml at 4.0 C. How many water molecules are present in 2.56 ml of water at this temperature?

7 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships 7 Percent Composition & Chemical Formulas 27. Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is C 9H 10O. (a) Calculate the percent composition by mass of C, H, and O in cinnamic alcohol. (b) How many molecules of cinnamic alcohol are contained in a sample of mass g? 28. (a) How many grams of oxygen are in 13.5 grams of aluminum carbonate? (c) How many grams of fluorine are in g of uranium hexafluoride? 29. Monosodium glutamate (MSG), a food-flavor enhancer, has been blamed for "Chinese restaurant syndrome," the symptoms of which are headaches and chest pains. MSG has the following composition by mass: percent C, 4.77 percent H, percent O, 8.29 percent N, and percent Na. What is its molecular formula if its molar mass is 169 g? 30. Mass spectrometry can also be used to determine the mass of molecular substances. Hydrogen has two stable isotopes 1 1H and H, and sulfur has four stable isotopes, 16 S, 16 S, 16 S, and 16 S. How many peaks would you observe in the mass spectrum of the positive ion H 2S +?

8 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships A 12.24g sample of an organic ether containing only the elements carbon, hydrogen and oxygen is burned in oxygen gas, and the combustion products carbon dioxide and water are collected and massed. The carbon dioxide weighed g and the water weighed g. What is the empirical formula of the ether? Writing Equations 32. Balance the following equations. (a) KNO 3 KNO 2 + O 2 (b) NH 4NO 3 N 2O + H 2O 33. Write a balanced chemical equation for each of the following reactions. (a) At 1000 o C ammonia gas reacts with oxygen gas to form gaseous nitric oxide (NO) and water vapor. This reaction is the first step in the commercial production of nitric acid. (b) The complete combustion of benzene C 6H 6. (d) Sulfuric acid reacts with barium chloride in water to yield hydrochloric acid and a precipitate of barium sulfate. Also write the net ionic equation for this reaction. (e) Iron rusts.

9 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships The particle diagrams below represent the reaction between two nonmetals, A2 and Q2. (a) Using the symbols A and Q, write the chemical formula of the product. (b) Identify the type of chemical bond in the product. (c) Compare the total mass of the reactants to the total mass of the products. Stoichiometry & Limiting Reagents 35. Fermentation is a complex chemical process of wine making in which glucose is converted into ethanol and carbon dioxide: C 6H 12O 6 2C 2H 5OH + 2CO 2 glucose ethanol Starting with g of glucose,, what is the maximum amount of ethanol in grams and in liters that can be obtained by this process? (Density of ethanol = g/ml.) 36. Consider the reaction 2A + B ABA In the box diagram shown, which reactant, A or B, is the limiting reagent? In the empty box, draw a molecular model representation of the amounts of reactants and products remaining after the reaction is finished. (Open circles are A and dark circles are B. )

10 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships Each copper(ii) sulfate unit is associated with five water molecules in crystalline copper(ii) sulfate pentahydrate (CuSO 4 5H 2O). When this compound is heated in air above 100 C, it loses the water molecules and also its blue color: CuSO 4 5H 2O CuSO 4+ 5H 2O If 9.60 g of CuSO 4 are left after heating g of the blue compound, calculate the number of moles of H 2O originally present in the compound. 38. A common laboratory preparation of oxygen gas is the thermal decomposition of potassium chlorate (KC1O 3). Assuming complete decomposition, calculate the number of grams of O 2 gas that can be obtained from 46.0 g of KC1O 3. (You will need a balanced equation; the products are KC1 and O 2.) 39. Nitric oxide (NO) reacts instantly with oxygen gas to form nitrogen dioxide (NO 2), a dark-brown gas: 2NO(g) + O 2(g) 2NO 2(g) In one experiment mole of NO is mixed with mole of O 2. Calculate which of the two reactants is the limiting reagent. Calculate also the number of moles of NO 2 produced. 40. Consider the reaction MnO 2 + 4HC1 MnCl 2 + C H 2O If 0.86 mole of MnO 2 and 48.2 g of HC1 react, which reagent will be used up first? How many grams of C1 2 will be produced?

11 AP Chapter 1, 2, & 3: Atoms & Molecules, and Mass Relationships Ethylene (C 2H 4), an important industrial organic chemical, can be prepared by heating hexane (C 6H 14) at 800 C: C 6H 14 C 2H 4 + other products If the yield of ethylene production is 42.5 percent, what mass of hexane must be reacted to produce 481 g of ethylene? 42. One of the reactions that occurs in a blast furnace, where iron ore containing iron(iii) oxide is converted to cast iron, is Fe 2O 3 + 3CO 2Fe + 3CO 2 Suppose that 1.64 x 10 3 kg of Fe are obtained from a 2.62 x 10 3 kg sample of iron ore. Assuming that the reaction goes to completion, what is the percent purity of Fe 2O 3 in the original sample?