Chemistry Midterm Review DeMario 2007

Question One Describe the atomic model for each scientist listed. Be sure to mention information about the experiment and the location of the subatomic particles. Describe the atomic model for each scientist listed. Be sure to mention information about the experiment and the location of the subatomic particles. 1. Dalton 2. Thomson 3. Rutherford 4. Bohr 5. Modern View Answer

Answer 1 Dalton – indivisible, solid sphere (no subatomic particles) Dalton – indivisible, solid sphere (no subatomic particles) Thomson- “plum pudding model” electrons are evenly distributed throughout a mass of protons. Model based on his cathode ray experiment Thomson- “plum pudding model” electrons are evenly distributed throughout a mass of protons. Model based on his cathode ray experiment Rutherford- discovered mostly empty space surrounding a dense positively charged nucleus using through the gold foil experiment Rutherford- discovered mostly empty space surrounding a dense positively charged nucleus using through the gold foil experiment Bohr- believed in a small positively charged nucleus containing the protons and neutrons surrounded by electrons in ORBITS of specific energy levels Bohr- believed in a small positively charged nucleus containing the protons and neutrons surrounded by electrons in ORBITS of specific energy levels Modern View- Also called the wave- mechanical model and the quantum model similar to Bohr but electrons are in regions of high probability based on energy level, and orbital. Modern View- Also called the wave- mechanical model and the quantum model similar to Bohr but electrons are in regions of high probability based on energy level, and orbital.

Question 2 Compare the charge, size, and location of a proton, neutron, and electron. Compare the charge, size, and location of a proton, neutron, and electron. Answer 2

Type of subatomic particle Size in amu Charge Location in an atom Proton1+1nucleus Neutron10nucleus Electron1/2000 Electron clouds surrounding nucleus

Question 3 Explain why the following two elements are isotopes. State the number of protons, electrons, and neutrons each isotope possesses. Explain why the following two elements are isotopes. State the number of protons, electrons, and neutrons each isotope possesses.

Answer 3 They are isotopes because each have a different # of neutrons but the same number of protons and electrons. They are isotopes because each have a different # of neutrons but the same number of protons and electrons. Sn -121 has 50 p +, 50 e -, 71 n 0 Sn -121 has 50 p +, 50 e -, 71 n 0 Sn- 119 has 50 p +, 50 e -, 69 n 0 Sn- 119 has 50 p +, 50 e -, 69 n 0

Question 4 List the seven metalloids List the seven metalloids

Answer 4 BSi, Ge, As Sb, Te Sb, Te At At

Question 5 Why is the formation of a solution a physical change while the ability to react with a chemical considered a chemical change? Why is the formation of a solution a physical change while the ability to react with a chemical considered a chemical change?

Answer 5 “reacting” indicates a change in the physical properties of an element resulting in a new compound. “reacting” indicates a change in the physical properties of an element resulting in a new compound. Formation of a solution is a physical property because a new compound has not been formed. Evaporation of the water would leave the original compound behind. (ex. salt dissolving in water) Formation of a solution is a physical property because a new compound has not been formed. Evaporation of the water would leave the original compound behind. (ex. salt dissolving in water)

Question 6 List Properties of a metal and a nonmetal. List Properties of a metal and a nonmetal.

Answer 6 Metals Metals Form cations Form cations Shiny Shiny Malleable Malleable Ductile Ductile Good conductors Good conductors Low electronegativites and IE Low electronegativites and IE Solids except Hg Solids except Hg Nonmetals Nonmetals Brittle Dull Poor conductors High electronegativities and IE

Question 7 Define allotrope. Define allotrope.

Answer 7 One or more molecular forms of an element in the same physical state; One or more molecular forms of an element in the same physical state; Example: O 2 and O 3 Example: O 2 and O 3 Carbon: graphite, diamond, Carbon: graphite, diamond, buckyballs buckyballs Allotropes are composed of the same element but different composition of atoms results in different properties and different structures. Allotropes are composed of the same element but different composition of atoms results in different properties and different structures.

Question 8 What is the correct formula for Cobalt(III) bromide? What is the correct formula for Cobalt(III) bromide?

Answer 8 CoBr 3

Question 9 What form of matter cannot be decomposed? What form of matter cannot be decomposed?

Answer 9 Element

Question 10 What happens to a nonmetal ion when it becomes a negative ion? What happens to a nonmetal ion when it becomes a negative ion? Mention difference in # of electrons Mention difference in # of electrons Changes in radius Changes in radius

Answer 10 Gains electrons Gains electrons Radius increases Radius increases

Question 11 What is the name of the property that indicates an element’s desire to attract electrons and which element has the greatest attraction? What is the name of the property that indicates an element’s desire to attract electrons and which element has the greatest attraction?

Answer 11 Electronegativity Electronegativity Fluorine Fluorine

Question 12 What are the terms used to identify a pure substance? What are the terms used to identify a pure substance? What are the terms used to identify a mixture? What are the terms used to identify a mixture?

Answer 12 Element and compound Element and compound Heterogeneous and Homogeneous Heterogeneous and Homogeneous

Question 13 What is the difference between an excited state electron and a ground state electron? What is the difference between an excited state electron and a ground state electron?

Answer 13 Ground state electrons are in the lowest energy state Ground state electrons are in the lowest energy state Excited state electrons have absorbed energy allowing them to jump to a higher energy level. Excited state electrons have absorbed energy allowing them to jump to a higher energy level.

Question 14 What are the three assumptions made regarding particle behavior in the KMT [Kinetic Molecular Theory]?

Answer Gas particles are small, hard spheres with insignificant volumes 2. Particle’s motion is rapid, constant, and random straight-line motion 3. Particle collisions are perfectly elastic

Question 15 What is the name for each type of phase change? What is the name for each type of phase change? 1. Solid  liquid 2. Liquid  gas 3. Gas  liquid 4. Liquid  solid 5. Solid  gas

Answer Melting 2. Boiling or vaporization 3. Condensation 4. Freezing / solidification 5. Sublimation

Question 16 According to Avogadro's Hypothesis two samples of gas that have the same volume and are at the same temperature and pressure will _______________. According to Avogadro's Hypothesis two samples of gas that have the same volume and are at the same temperature and pressure will _______________.

Answer 16 Have the same numbers of particles Have the same numbers of particles

Question 17 Thermal energy from a cold pack travels in which direction when applied to the leg? Thermal energy from a cold pack travels in which direction when applied to the leg?

Answer 17 Hot  cold Leg  cold pack

Question 18 Under what conditions will a real gas behave ideally?

Answer 18 High temperature [so that the particles are moving fast] High temperature [so that the particles are moving fast] Low pressure [ so that particles are far apart to avoid attraction] Low pressure [ so that particles are far apart to avoid attraction]

Question 19 What is the % composition by mass of carbon in carbon dioxide [gram-formula mass 44 grams/mole]? What is the % composition by mass of carbon in carbon dioxide [gram-formula mass 44 grams/mole]?

Answer % C

Question 20 Why does calcium have similar chemical properties to barium? Why does calcium have similar chemical properties to barium?

Answer 20 Both are Group 2 elements Both are Group 2 elements Both have the same number of valence electrons Both have the same number of valence electrons

Question 21 Which of the following terms indicate a chemical property and which indicate a physical property? Which of the following terms indicate a chemical property and which indicate a physical property? 1. Flatten 2. Conduct 3. Corrode 4. Drawn into a wire 5. React

Answer 21 Chemical Chemical Corrode Corrode react react Physical Physical Flatten Drawn Conduct

Question 22 What is the charge on a I-127 nucleus? What is the charge on a I-127 nucleus?

Answer

Question 23 Name the type of element as it appears in the order below. Ge  K  Ar  Br

Answer 23 Ge  K  Ar  Br Metalloid, metal, noble gas, nonmetal

Question 24 How many electrons are contained in an Cu 2+ ion?

Answer electrons

Question 25 Which electron configuration represents the electrons of atom of sodium in the excited?

Answer

Question 26 If an element is shiny and a good conductor, what type of element is it? If an element is shiny and a good conductor, what type of element is it?

Answer 26 Metal

Question 27 Compare the number of subatomic particles that compose N-14 and F-19.

Answer 27 N-14 N-14 Protons 7 Protons 7 Electrons 7 Electrons 7 Neutrons 7 Neutrons 7 F-19 F-19 Protons 9 Electrons 9 Neutrons 10 F-19 has two protons, two more electrons, and three more protons than N-14

Question 28 Which of the following is a molecular formula? CH 4 C 3 H 6

Answer 28 C3H6C3H6C3H6C3H6

Question 29 In what ratio, will a calcium ion combine with a phosphide ion?

Answer 29 Ca 3 P 2 3:2

Question 30 What is the melting point of this substance? s l g 280 k 380 k

Answer k

Question 31 Describe the difference between a particle diagram of a solid, liquid, and gas.

Answer 31 Solid particles are packed tightly Solid particles are packed tightly Liquids are close but have some space for movement Liquids are close but have some space for movement Gases are far apart Gases are far apart

Question 32 Compare the atomic radius of Ca to Mg and Sr.

Answer 32 The atomic radius falls in the middle of Mg and Sr.

Question 33 State the trend for each of the following properties across a period. State the trend for each of the following properties across a period. Ionization Energy Ionization Energy Electronegativity Electronegativity Atomic radius Atomic radius

Answer 33 IE and Electronegativity increases across the period IE and Electronegativity increases across the period Atomic Radius decreases Atomic Radius decreases

Question 34 State the trend for each of the following properties down a group. State the trend for each of the following properties down a group. Ionization Energy Ionization Energy Electronegativity Electronegativity Atomic radius Atomic radius

Answer 34 IE and Electronegativity decreases across the period IE and Electronegativity decreases across the period Atomic Radius increases Atomic Radius increases

Question 35 Which segments represent an increase in PE and which represent an increase in KE? k 380 k A B C

Answer 35 1, 2, 3 show an increase in KE because the temperature is increasing 1, 2, 3 show an increase in KE because the temperature is increasing A, B, C show an increase in PE because temperature remains constant until the phase change is complete. A, B, C show an increase in PE because temperature remains constant until the phase change is complete.

Question 36 Is this a endothermic or exothermic reaction? k 380 k A B C

Answer 36 Endothermic because energy is being absorbed. Endothermic because energy is being absorbed.

Question 37 Why do the formulas for calculating the heat of fusion and the heat of vaporization not include a change in temperature as one of the variables?

Answer 37 The temperature is not changing during a phase change. (P.E. is increasing)

Question 38 Calculate the number moles in 48 grams of CO. Calculate the number moles in 48 grams of CO.

Answer moles

Question 39 What is the combined gas law?

Answer 39

Question 40 What is the relationship between Celsius and Kelvin?

Answer 40 Kelvin = Celsius temp + 273