Fall Final Study Guide Answers

Name: ____________________________________________ Date: ______________________________ Period: ______ Study Guide for Chemistry Fall Final 2019 Midterm Exam Facts r The midterm exam is scheduled for __________________. You will have 80 minutes. r The midterm exam is cumulative. This means it covers everything we have studied in chemistry this semester. How Does the Midterm Exam Affect My Grade? r The midterm exam counts 5% of your overall Quarter grade for chemistry (10% midterm/final) r Students historically score within 10% of their test average on the midterm exam. So, If Polly Perfect’s test average is an 85%, she can expect to score 75-95% on the midterm – if she studies! What Should I Review/Study? r Unit Tests and Quizzes r Previous study guides r Online review resources (both on the midterm page and the unit pages) r This Study Guide & Answer Key Which Reference Sheets Can I Use on the Midterm? r Student Produced front and back, one page (8 x 11.5) notes (hand-written front & back) r Periodic Table (class set) r Unit Conversion Factors Reference Sheet (class set) r Student Produced Periodic Table Flipbook What if I Need Extra Help? r It is much better to study a little every day than to leave things until the last minute. Seek help early. r Find a study buddy/friend/significant other  who is in chemistry and study together. Last Piece of Advice Chemistry is a challenging college preparatory class. Recognize that your college/university instructors will not provide you with a study guide that covers “everything” that will be on their exams. In fact, most professors won’t provide you with a study guide at all. You can thank Mrs. Macedo for putting together this study guide for you. Please view this as a “guide,” and understand it will not tell you everything that is on the midterm exam. However, if you are able to answer all of the questions successfully in this guide, and you truly understand all of the bulleted concepts listed for you to study, your chances of success are very good. Unit 1– Measurements, Scientific Method, Math 1. How are matter and mass related? Mass is a measure of the amount of matter in an object 2. Describe the difference between mass and weight. Weight is the effect of the earth’s gravitational pull on mass. That’s why you don’t weigh the same on the earth and the moon. But you do have the same mass. 3. What is volume? Volume is the amount of space an object takes up. It’s commonly measured in liters (L). 4. Graphing: Table 1 shows data collected about the study habits of law school students. For each candidate, they recorded how much time they spent studying and the score they received on the test. Graph the following data 1 on the graph to the right, then answer the questions. Remember to include a title, axis labels, and an 5. 6. 7. 8. 9. appropriate scale. a. What is the dependent variable? Score Earned b. What is the independent variable? Days studied c. Draw a line of best fit on the graph. d. Does the graph have a positive or negative correlation? Positive. e. If a student studied for 10 days, what would you expect their score to be? ~28 i. Is this extrapolation or interpolation? Extrapolation because the estimation is out of the range of the given data. f. Write a sentence describing the relationship between days studied and score earned. More days studied result in a higher test score. What is the difference between a pure substance and a mixture? Pure substances have 1 type of particle, pure substances can be compounds or elements. Mixtures contain 2 or more types of particles. Classify each of the following as a compound, element, or mixture: a. Salt (NaCl) Compound b. Tin (Sn) Element c. Lemonade (H2O & C6H12O6 & …) Mixture What is a physical property? What is a chemical property? A physical property is a characteristic that can be observed or measured without changing the objects identity (examples: density, color, taste, hardness, and melting point). Chemical properties are the ability or inability of a substance to combine with or change into a new substance. Chemical properties cannot be observed without changing the identity of the substance (For example, to determine if a substance is combustible, then I must burn it. This changes the substance.) Classify each of the following as a physical property or a chemical property: a. ability to conduct heat Physical b. ability of a compound to decompose into its elements Chemical c. compressibility Physical d. ability of a compound to change from a gas to a liquid Physical Determine the measure (to the correct number of sig figs) for the following tools: From top to bottom, left to right: 6.35 mm, 48 mL, 142.1 g. 10. What is the equation for percent error? 2 Percent Error = ¿ Experimental−Actual∨ ¿ ¿ Actual x 100 11. Describe accuracy and precision. Accuracy: How close a measured value is to the true (actual or theoretical value). Precision: How close a series of measurements are to each other. 12. At a track meet, you time a friend running 100 m at 11.00 seconds. The official time of her race is 10.87 seconds. What is your % error? ¿ Percent Error = ¿ 11.00 sec−10.87 sec∨ 10.87 sec ¿ x 100 = 1.196 % 13. What is the percent error of a length measurement of 0.229 cm if the correct value is 0.225 cm? ¿ Percent Error = ¿ 0.229 cm−0.225 cm∨ 0.225 ¿ x 100 = 1.78% 14. What are the SI units for length? meter for mass? Gram. for volume? Liter for temperature? kelvin 15. What is the density of 5.3 lbs of oak that has a volume of 25.7 cm 3? Give your answer in g/ml! First, convert your mass to grams because we want an answer in g/mL. We also know that 1 cm 3 = 1 mL, so 3 25.7 cm = 25.7 mL. 5.3 lbs 453.6 g = 2404.08 g 1 lbs Density = mass/volume Density = 2404.08 g / 25.7 mL Density = 94 g / mL 16. How many kilometers in 15 miles? 15 miles 1.609 km = 24.135 km --> 24 km 1 mile 17. How many seconds are in 1 year? Show your work in proper format!! 1 year 365 days 24 hr 60 min 60 seconds = 31,536,000 seconds --> 30,000,000 seconds 1 year 1 day 1 hr 1 min 18. How many cm in a 100 yard football field? Show your work in proper format!! (Hint: 2.54 cm = 1 inch) 100 yard 3 ft 12 in 2.54 cm 9,144 cm --> 9000 cm 1 yard 1 ft 1 in 19. Calculate the following quantities using dimensional analysis a. 100 cm = 1 m b. 1000 cm = 10 m c. 752 m = 0.752 km d. 53 km = 53,000 m 20. How many significant figures does each number have? a. 0.00003 --> 1 b. 0.003050 --> 4 c. 8,000,000 --> 1 d. 500.033 --> 6 e. 203.050 --> 6 f. 4.0 x 103 --> 2 21. Perform the calculations and round off each answer to the correct number of significant figures. a. 162.1g + 38.73g + 1.554g = 202.384 g --> 202.4 g b. 21.9m - 6.34m + 157m = 185.24 m --> 185 m c. 9.88cm x 7.2 cm = 71.136 cm --> 71 cm d. 44.75 g / 1.62 L = 27.62 g/L --> 27.6 g/L 22. Take the following out of scientific notation and write them in long/standard form: a. 4.5 x 103 = 4,500 3 a. b. c. d. b. b. 3.90 x 10-4 = 0.000390 c. c. 6.02 x 105 = 602,000 23. Express the following quantities in scientific notation 600 = 6 x 102 7770 = 7.77 x 103 0.125 = 1.25 x 10-1 0.0000025 = 2.5 x 10-6 Unit 2 – Heat & Energy in the Earth’s System 24. Explain if the shape is definite and if the volume is definite for: a. Solid definite Shape and definite volume. b. Liquid indefinite shape and definite volume. c. Gas indefinite shape and indefinite volume. 25. Use the heating curve to the right to answer the following questions: a. Label the states of matter on the graph. Solid: A-B, Liquid: C-D, and Gas: E-F b. Label the phase changes on the graph. Solid Melting: B-C, Vaporizing: D-E c. What is happening to the energy at line BC? Kinetic energy is constant because temperature is constant. Potential energy is increasing because particles are spacing out (solid melts into liquid). d. What is happening to the energy at line DE? Kinetic energy is constant because temperature is constant. Potential energy is increasing because particles are spacing out. e. What is the boiling point of the substance? About 50 degrees Celsius f. What is the freezing point of the substance? About 25 degrees Celsius 26. Sketch the corresponding cooling curve for question 28. Label the states of matter, the phase changes, and discuss the changes in KE and PE along each line. 27. What are the layers of the earth? How does density relate to their order? From lowest to highest density: Crust, Mantle, Core. Denser layers are deeper. 28. What is the equation for density? Density = mass/volume 29. What is volume of a cube that weighs 250 g and has a density of 3.5 g/mL? Density = mass/volume. 3.5g/mL = 250g/volume Volume = 875 mL 30. What is the mass of a substance that has a volume of 30 mL and a density of 40 g/ mL? Give your answer in kilograms. Density = mass/volume 40 g/mL = mass/30 mL 4 Mass = 1200 g Convert 1200 g to kg: 1200 g x 1 kg/1000 g = 1.2 kg. Round to 1 significant figure --> 1 kg 31. You are given a blue liquid. You determine the mass to be 64.8 g. You observe the volume to be 54.0 cm 3. What is the liquid’s density? Will this liquid float on top of water? Why or why not? From the conversion chart: 1 cm3 = 1 mL, thus 54.0 cm3 = 54 mL Density = mass/volume Density = 64.8 g / 54 mL = 1.2 g/mL It would sink under water, because it is denser (water’s density is 1 g/mL) 32. What is the density (in g/mL) of an unknown alien rock whose mass is 3.28 kg and volume is determined by water displacement (see graduated cylinders below)? Beaker without rock = 200 mL Beaker with rock = 260 mL Volume of rock = 260 mL – 200 mL = 60 mL (significant figures are funky on this one, ignore it) Mass of rock = 3.28 kg = 3280 g (use dimensional analysis) Density = 3280g / 60 mL = 54.7 g/mL 33. You have a rectangle with dimensions 3.20cm x 2.10cm x 8.23cm. It is made of aluminum (density = 2.7g/cm 3). What is the mass of your rectangle? Volume = 3.20cm x 2.10cm x 8.23cm = 55.3056 cm 3 2.7 g/cm3 = mass / 55.3056 cm3 Mass = 149.325 g --> 150 g 34. What is energy? What are the two types of energy? What are the 3 types of energy transfer? Energy is a measure of work (“how much energy do I need to do ______). Kinetic energy is the energy of motion (including heat). Potential energy is a stored energy. The three types of energy are: conduction, convection, and radiation. 35. Compare conduction, convection and radiation energy transfer. Label each picture below by the type of transfer it shows. 1. Convection within the water in the pot. 2. Radiation from the sun to the pool. 3. Conduction from the stove to the metal teapot. 5 36. Use the diagram above and answer the following questions: a. Where does the heat come from that drives this convection current in the mantle? The core. b. Where is the temperature of the mantle material greater, at point A or B? Explain why. Two possible answers: Point A is hotter because it’s closer to the core or Point B is hotter because it less dense (it floats over Point A). c. How does this convection cell affect the crust material above it? d. What type of plate boundary would be found at point C? Convergent plate boundary. e. What type of plate boundary would be found at point B? Divergent plate boundary. 37. Label each figure by writing the type of plate boundary it shows. 1. Divergent 2. Convergent 3. Transform 38. What is calorimetry & what is a calorimeter? What is specific heat? What are the units of specific heat? What is the specific heat of water? Calorimetry is act of measuring the heat absorbed or released during reactions. A calorimeter is a device used to measure the heat released/absorbed. Specific heat is the amount of energy required to raise the temperature of a substance. Specific heat is how many joules it takes to raise the temperature of 1 gram of substance by 1 degree Celsius (joules/gram °C). It can also be shown in calories instead of joules. 39. A student must use 225 mL of hot water in a lab procedure. Calculate the amount of heat required to raise the temperature of 225 g of water from 20.0°C to 100.0°C. Water’s specific heat is 4.184 J/g °C. Q = mCΔT Q = heat (J or Cal) M = mass (g) C = specific heat (J/g °C or cal/g °C) ΔT = change in temperature (°C) Q = (225 g) x (4.184 J/g °C) x (80.0 °C) Q = 75,312 J --> 75,300 J. 40. A 40.0 g sample of ethanol releases 2952 J as it cools from 50.0 °C. Calculate the final temperature of the ethanol. (Cp ethanol = 2.46J/g°C) Q is negative because its releasing energy (absorbing energy is positive). -2952 J = (40 g) x (2.46 J/g °C) x (ΔT) ΔT = - 30 °C The sample’s temperature went down by 30°C (shown by negative sign). 6 Starting temperature was 50.0°C, then it cooled down by 30°C. Your final temperature is 20.0 °C. 41. Calculate the heat change involved when 2.00 kg of water is heated from 20.0°C to 99.7°C in an electric kettle. 2 kg = 2000 g (use dimensional analysis) ΔT = Final temperature – initial temperature = 99.7 °C - 20.0 °C = 79.7 °C. Q = (2000 g) x (4.184 J/g °C) x (79.7 °C) Q = 666,929 J --> 667,000 J 42. Calculate the specific heat capacity of titanium if a 43.56 g sample absorbs 0.476 kJ as its temperature changes from 20.13°C to 41.06°C. We need to calculate the specific heat capacity, C, of titanium. Convert into joules: 0.476 kJ = 476 J (dimensional analysis) ΔT = Final temperature – initial temperature = 41.06 °C - 20.13 °C = 20.93 °C. 476 J = (43.56 g) x C x (20.93 °C) C = 0.5221 J/g °C 43. A 63.5 g sample of an unidentified metal has a specific heat capacity of 1.23J/g°C. How much energy (in calories) is absorbed when its temperature changes by 4.56°C? Unit 3 – The Atom& Nuclear Chemistry 44. Name and describe the 3 subatomic particles (describe their charge, location in the atom, & mass) Proton: Positive (+ 1) particle with mass of 1 located in the nucleus (center of atom). Neutron: Neutral particle with mass of 1 located in nucleus. Electron: Negative (- 1) particle with small mass. Located outside of nucleus in electron cloud/shell/ring. 45. How do you find the neutrons in an atom? Using the following formula: protons + neutrons = mass 46. Define an ion. Define an isotope. An ion is an atom with a positive (+) or negative (-) charge. Isotopes are different forms of the same element (same proton and atomic number) but a different number of neutrons. This different results in a different mass. 47. Two isotopes of Iodine-127 and iodine-131. Compare their: a. atomic numbers: They have the same atomic number of 53. b. mass numbers: Iodine-127 has a mass of 127 while idodine-131 has a mass of 131. c. number of protons & neutrons: Both have 53 protons (like always, protons = atomic number). Iodine 127 has 74 neutrons while iodine-131 has 78 neutrons. d. complete nuclear symbols 48. Fill in the missing data in the table below symbol He W Pb U Mo 2 74 82 92 42 4 184 210 235 95 # of protons 2 74 82 92 42 # of neutrons 2 110 128 143 53 # of electrons 2 74 82 92 42 Atomic # Mass # 49. Fill in the following table. Watch out for IONS and ISOTOPES! Name Atomic Mass A Charge Symbol ( Z X ) (hyphen notation) Number Number Calcium—39 39 Bismuth - 207 207 83 Technetium - 98 Protons Neutrons Electrons Ca+2 20 39 20 19 18 Bi−3 83 207 83 124 86 43 98 43 55 42 20 98 43 Tc+1 7 Barium - 138 Xenon—130 138 56 Ba+2 130 54 Xe 56 138 56 82 54 54 130 54 76 54 50. Draw Bohr Models for elements with the following atomic numbers: 4, 9, 12, 18, 19. a. How many valence electrons does each one have? Atomic number 4: 2 valence electrons. Beryllium will form a +2 cation (lose 2 electrons). Atomic number 9: 7 valence electrons. Fluorine will form a –1 anion (gain 1 electron). Atomic number 12: 2 valence electrons. Magnesium will form a +2 cation (lose 2 electrons). Atomic number 18: 8 valence electrons. Argon will not form an ion; it has a stable octet (full outer shell). Atomic number 19: 1 valence electron. Potassium will form a +1 cation (lose 1 electron). b. Will they form an ion? If so, will they gain or lose electrons? What will the ion’s charge be? See above 8 51. What are valence electrons? What is the octet rule? What does it mean? Valence electrons are the electrons on the outermost shell of an atom. Elements are most stable when they have 8 valence electrons. Elements will lose and gain electrons to reach a full outer shell of 8 electrons (octet rule). 52. Describe anions. Describe cations. Anions are ions with a negative charge. Cations are ions with a positive charge. 53. Which statement best describes the density of an atom’s nucleus? a. The nucleus occupies most of the atom’s volume but contains little of its mass. b. The nucleus occupies very little of the atom’s volume and contains little of its mass. c. The nucleus occupies most of the atom’s volume and contains most of its mass. d. The nucleus occupies very little of the atom’s volume but contains most of its mass. 54. What is Radioactivity? How do half-lives relate to radioactivity? Unstable substances exhibit radioactivity. Unstable elements emit radioactive particles through radioactive decay (alpha, beta, positron, and gamma) to become more stable. When elements emit these particles, the elements change (transmutation) into more stable elements/isotopes. Half-life is the time it takes for half a sample to decay. 55. Uranium-238 is one of the radioactive nuclides sometimes found in soil. It has a half-life of 580 years. What percentage of a sample is left after 1740 years? 1740 years / 580 years = 3 half-lives. Looking for percentage, start at 100% and go through 3 half-lives. 100% --> 50% --> 25% --> 12.5% percent of the sample is left after 1740 years. 56. The half life of plutonium-239 is 24,110 years. If an original mass is 100.g, how much will be left after 96,440 years? 96,440 years / 24,110 years = 4 half-lives 100. g --> 50.0 g --> 25.0 g --> 12.5 g --> 6.25 g remain after 96,440 (4 half-lives). 57. What is the neutron –proton ratio of the most stable nuclei according to the ‘band of stability’? A ratio of 1 neutron to 1 proton (1:1) is the most stable nuclei. 58. Describe what happens in the following nuclear processes. a. alpha – 42He is emitted. b. beta – 0-1e is emitted. c. gamma – 00Y (gamma sign, not the letter Y) is emitted. d. Positron emission – 0+1e is emitted. 59. Complete the following nuclear reactions, then give the type of decay: a. 23993Np 0-1β + 23994Pu Type of decay: Beta decay 15 15 0 b. 8O  7N + +1e, Type of decay: Positron decay c. 94Be  52He + 42He Type of decay: Alpha decay d. 33*15P 3315P + 00Y Type of decay: Gamma decay 60. Write the following nuclear decay equations: An unstable isotope goes through alpha decay to produce Barium-138. 142 4 138 Ce  He + Ba 58 2 56 Ru-103 goes through positron emission. 103 0 103 44Ru  +1e + 43Tc Beta decay of Tin-119 resulted in a stable isotope and a gamma particle. 119 0 0 119 50Sn  -1e + 0Y + 51Sb Unit 4 – The Periodic Table 61. Name, by number, both the period and group that elements with atomic numbers 10, 16, & 3 are in. 10 – Neon, Period 2, Noble Gas 16 – Sulfur, Period 3, Chalcogens 3 – Lithium, Period 2, Alkali Metal 62. Mendeleev arranged the modern periodic table in order of increasing: a. atomic number b. atomic mass c. both of these 9 d. none of these 63. Why is cobalt (Co) placed before nickel (Ni) on the periodic table of the elements even though it has a higher average atomic mass than nickel? a. Nickel has one more proton. b. Cobalt was discovered first. c. Nickel has fewer electrons. d. Cobalt has a lower density. 64. Metals are located on the __left_ side of the staircase and nonmetals are located on the _right_ side. 65. Identify two characteristics of metals and two characteristics of nonmetals. Metals are shiny, ductile, malleable, higher melting/boiling points, mostly solids Nonmetals are brittle and poor conductors. 66. What are metalloids? Identify the elements that are commonly classified as metalloids. Exhibit some characteristics of metals and nonmetals – like they are semiconductors. 67. Identify the number of electrons for the following elements using the periodic table. What charge will they form? Se: Se has 34 electrons and 6 valence electrons. It will form a –2 ion (gain 2). N: Nitrogen has 7 electrons and 5 valence electrons. It will form –3 ion (gain 3). Cs: Cesium has 55 electrons and 1 valence electron. It will for a +1 ion (lose 1). P: Phosphorus has 15 electrons and 5 valence electrons. It will for a –3 ion (gain 3 electrons). Ne: Has 10 electrons and 8 valence electrons. It will not form an ion. 68. Which is more reactive, Sodium or Oxygen? Why? Sodium is more reactive because it is part of the alkali metal group, which is extremely reactive. Elements on the left table will generally be more reactive (?). 69. Which of the following atoms has the largest atomic radius? Barium, chlorine, iodine, or magnesium. 70. List the following atoms in order of increasing electronegativity: Na, I C, K, Br. K< Na < C < I < Br (Electronegativity increases as you move up and the right) 71. Identify the atom with the larger radius in each of the following pairs. a. S and O b. O and F c. Na and K Atom size increases as you move down and to the left. * Period (row) makes a larger size difference than group (family). 72. Iodine would have chemical properties most like a. manganese b. tellurium c. chlorine d. xenon (Xe) 73. Why does atomic radius decrease as you go across a period? Increase in protons pulling on the electrons, bringing them in closer and ultimately making a smaller radius 74. Why does electronegativity increase as you go up a family? Less shielding, so nucleus’ protons hold on to the electrons tighter. 75. Why are the noble gas elements so stable (inert)? They have a stable octet. 76. Define ionization energy, electronegativity, atomic radius, reactivity – Ionization energy: amount of energy required to remove an electron from an atom. Electronegativity: how badly an atom wants to gain/keep an electron. Atomic radius: the size of the atom from the nucleus to the outer electrons Reactivity: How likely an element is to react. 77. General Chemistry Concepts to Know: Parts of a graph, how to make one Parts of a data table, how to make one Lab equipment How to read a ruler, graduated cylinder, etc – DOUBT Lab Safety 10