Name: KEY Block: Date: Unit 2 Test Review

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1 Name: KEY Block: Date: Unit 2 Test Review Matter and Atomic Structure Complete the following problems to help prepare you for you Unit 2 Test. You more than likely will want to answer these questions on a separate piece of paper (unless you can write microscopically). In addition to these problems, review your notes, assignments (#29-44), labs, and chapter 3 & 4 in your textbook. 1. Classify each as an element (E), a compound (C), or a mixture (M). a. Brass Mixture b. Tungsten Element c. Sodium chloride Compound d. Air Mixture 2. Classify each of the following as a physical (P) or chemical (C) change. a. Evaporating alcohol Physical b. Sanding a table top Physical c. Grinding grain Physical d. Fermenting fruit juice Chemical 3. Which of these is a chemical property? a. Ice melts at 0 C b. Oxygen is a gas c. Helium is very nonreactive d. Sodium is a soft, shiny metal e. Water has a high specific heat capacity 4. Draw and explain on the molecular level the different phases of matter. Solid definite shape and volume, does not take the shape of the container; particles are tightly packed Liquid flows and had a constant volume, takes the shape of the container; particles are less closely packed and can move past one another Gas no definite shape or volume, takes the shape of the container and the entire volume; particles are far apart and can easily be compressed 5. If sodium melts at C and boils at C, what is its physical state at 80 C? At 250 C? 80ºC = Solid 250ºC = Liquid 6. What is a pure substance made up of more than one kind of atom called? Compound 7. Describe the difference between a compound and an element. Give two examples of each. A compound is made up of two or more different elements that are combined chemically. (Water, H2O and Carbon dioxide, CO2 and there is many, many more) An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. Only one type of atom (Sodium, Na and Argon, Ar and there are many, many more)

2 8. How can a solution be distinguished from a compound? A solution can be separated by physical means where a compound can only be separated by chemical means. 9. Define and give an example of each: a. Homogenous mixture a mixture that has constant composition throughout (14K gold, tap water) b. Heterogeneous mixture a mixture that does not blend smoothly throughout and is which individual substances remain distinct (oil and water, seawater) c. Suspension a type of heterogeneous mixture whose particles settle out over time and can be separated from the mixture by filtration (coffee grounds, muddy water) d. Solution homogenous mixtures in either solid, liquid, or gas states (air, brass-an alloy) 10. Nitrogen oxide (NO) and nitrogen dioxide (NO2) are both made up of nitrogen and oxygen. Can you assume that they will both have similar physical and chemical properties? Why or why not? No, you cannot assume they will have similar physical and chemical properties because, even though they are made up of the same elements, their proportions of each element are different. 11. An 18-L sample of element A (density 0.84 g/ml combines completely with a 4-L sample of element B (density 2.34 g/ml) to form the compound AB. What is the mass of the compound formed? 18 L (A) 1000 ml 0.84 g = g (A) 4 L (B) 1000 ml 2.34 g = 9360 g (B) 1 L 1 ml 1 L 1 ml g (A) g (B) = g (24500 g sig fig) or 24.5 kg 12. A substance breaks down into three component elements when it is heated. The mass of each component element is listed in the table below. What was the mass of the substance before it was heated? Component Mass (g) A B C = g 13. Silver iodine powder has been used as an antiseptic and as an agent to seed clouds for rain. Silver iodine is 45.9% silver by mass. If you separate a 50.0-g sample of silver iodine into its elements, silver and iodine, how much silver would you have? 50.0 g.459 = = 23.0 g (sig figs) 14. If 5 g of element A combines with 16 g of element B to form compound AB, how many grams of B are needed to form AB2? How many grams of B are needed to form AB3? AB2 compound AB2 contains twice as much B than AB, so 2 16 = 32 g AB3 compound AB3 contains three times as much B than AB, so 3 16 = 48 g 15. During a chemical reaction, g of carbon reacts with g of oxygen to form carbon monoxide gas. How many grams of carbon monoxide are formed in this reaction? = g 16. Ibuprofen has the chemical formula C13H18O2. It is 75.69% carbon, 8.80% hydrogen, and 15.51% oxygen. How many mg of carbon does a.2-g tablet of ibuprofen contain? MMMMMMMM CC MMMMMMMM CC 75.69% = = Mass C = = g (sig figs) gg gg

3 17. During a chemical reaction, g of hydrogen combined with oxygen to form g of water. How many grams of oxygen reacted? Mass O = Mass O = = g 18. Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO2). The masses of oxygen that combine with 12 g of carbon to form these two compounds are 16 g and 32 g, respectively. What is the ratio of the masses of oxygen in CO 2 /CO. 32 gg = 2 2:1 ratio 16 gg 19. Phosphorus and chlorine combine to form two different compounds. In one compound, 3.88 g of phosphorus combines with g of chlorine. In the other compound, 1.32 g of phosphorus combines with 7.56 g of chlorine. Do these data support the law of multiple proportions? Show your work Compound I = Compound II = CCCCCCCCCCCCCCCC II CCCCCCCCCCCCCCCC IIII = = 1.67 This data is NOT consistent with the law of multiple proportions. The law of multiple proportions states that the different masses of Y that combine with a fixed mass of X can be expressed as a ratio of small whole numbers, and 1.67 is not a whole number. 20. Ferric chloride is 34.4% iron and 65.6% chlorine by mass. A chemist analyzes three compounds that contain iron and chlorine. Her results are summarized in the data table below. Which of these compounds is likely to be ferric chloride? Explain your answer. Mass of the Sample Compound Mass of Fe (g) Mass of Cl (g) (g) I II III Compound I Fe = 37.2% Cl = 62.8% Compound II Fe = 34.4% Cl = 65.6% Compound III Fe = 34.4% Cl = 65.6% Compounds II and III have the same composition so are likely to be ferric chloride, but compound I does not have the some composition so is likely not ferric chloride. 21. The chemical formula for baking soda is NaHCO3. A g sample of baking soda contains g of sodium, 2.02 g of hydrogen, g of carbon, and g of oxygen. What is the mass percentage of each element in baking soda? = % Na = 1.20 % H = % C = % O The chemical formula for chalk is CaCO3. A 100-g sample of chalk contains 40 g of calcium, 12 g of carbon, and 48 g of oxygen. What is the mass percentage of each element in chalk? = 40 % Ca = 12 % C = 48 % O 100 What would be the mass of calcium in 200 g of chalk? = 80 g Ca

4 23. A 17.0-g sample of ammonia, NH3, contains 3.0 g of hydrogen. What percentage of ammonia is hydrogen? = 18 % H 17.0 How many grams of nitrogen does the sample contain? = 14.0 g N 24. Discuss the different models proposed by Dalton, Thomson, and Rutherford. Include a drawing of each of their models. Dalton the atom is the smallest, indivisible part of matter; no subatomic particles, solid ball (billiard-ball model) Thomson the atom has positive and negative parts to it; a positive region with negative particles spread throughout (plum-pudding model) Rutherford the atom has a small, dense, central nucleus surrounded by mostly empty space; positive nucleus with electrons surrounding (nuclear atom) 25. Describe Rutherford s gold foil experiment and why he was able to determine that an atom has a positive nucleus where all the atom s mass is and the rest is mostly empty space with electrons moving around it in. During Rutherford s gold foil experiment, a beam of alpha particles bombarded a thin gold foil. Most of the alpha particles went through the gold foil. However, a few of them bounced back, some at large angles. He was able to determine that an atom has a positive nucleus is because of those alpha particles (positive) that bounced back were repelled by the positive nucleus and those passing far from the nucleus were only slightly deflected. Since most of the alpha particles passed through, he concluded the nucleus contains all the mass because the rest of the atom is empty space for the electrons to move around in. 26. Complete the table for the following elements without using a periodic table. Element # of # of # of Atomic Atomic # Protons Electrons Neutrons Mass Manganese (Mn) Sodium (Na) Bromine (Br) Yttrium (Y) What is an isotope? Atoms with the same number of protons (same element) but different numbers of neutrons. 28. Give the number of protons, electrons, and neutrons in each of the following atoms. a Ag p+ 47, e - 47, n 0 61 (108-47=61) b Ca p+ 40, e - 40, n 0 20 (40-20=20) c Na p+ 11, e - 11, n 0 12 (23-11=12) 29. How many neutrons does europium-151 have? What is the isotope s mass number? 151 mass # 63 p + = 88 n 0

5 30. Neon has two isotopes: neon-10 and neon-12. a. Which isotope has the greater mass? Neon-12 b. Which has more neutrons? Neon-12 c. Which has more protons? They have equal number of protons d. Which has more electrons? They have equal number of electrons 31. Use the table below to calculate the atomic mass of element X. then use the periodic table to identify the element. Show all your work. Isotope Mass (amu) Percent Abundance 16 X X X = ( ) + ( ) + ( ) = = = 16.0 amu (sig figs) which is oxygen 32. Magnesium has three isotopes. Magnesium-24 has a percent abundance of 78.99%. Magnesium- 26 has a percent abundance of 11.01%. What is the percent abundance of magnesium-25? Assume that there are no other magnesium isotopes = 10.00% Mg A sample of hydrogen is 99% 1 H, 0.8% 2 H, and 0.2% 3 H. What is its average atomic mass? = (1 0.99) + ( ) + ( ) = = = 1 amu (sig figs) 34. Calculate the atomic mass of iridium. Iridium has two isotopes. Iridium-191 has a mass of amu and a percent abundance of 37.58%. Iridium-193 has a mass of amu and a percent abundance of 62.42%. Show all your work = ( ) + ( )= = = amu (sig figs) 35. An element has three naturally occurring isotopes. Information about each isotope is summarized below. Isotope Mass (amu) Percent Abundance Isotope Isotope Isotope a. Find the atomic mass of this element. Show all your work = ( ) + ( ) + ( ) = = = amu (sig figs) b. Identify the element, using the periodic table. Magnesium c. Write each isotope in symbolic notation Mg Mg Mg

6 36. Fill in the data table below. Nuclear Particle Mass Charge Symbol(s) Alpha 4 2 α or He Beta 0-1 β or 0 1 e Gama 0 0 γ 37. Americium-241 ( 241 Am) undergoes alpha decay (inside a smoke detector) Am Np He 38. Iodine-131 ( 131 I) undergoes normal beta decay (used in therapy for hyperthyroidism) I Xe e 39. Fluorine-18 ( 18 F) undergoes positron emission (one of the radionuclides used in PET scans) F O e 40. Technetium-99m ( 99m Tc) undergoes gamma decay to form 99 Tc (a diagnostic radioactive tracer used to locate tumors, the m indicates a metastable excited nuclear state) Tc Np + γ