2. Which is NOT considered matter? (A) air (B) lead (C) sugar (D) sunlight. 4. Which of the following is a metalloid? (A) Se (B) Sr (C) Si (D) Sn

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1 Midterm Review Packet ANSWER KEY 01/26/2014 Multiple Choice Question 1. Which part of an atom is positively charged? (A) proton (B) neutron (C) electron (D) shells 2. Which is NOT considered matter? (A) air (B) lead (C) sugar (D) sunlight 3. The Group VIIA (7A) elements are called (A) alkali metals (C) noble gases (B) alkaline earth metals (D) halogens 4. Which of the following is a metalloid? (A) Se (B) Sr (C) Si (D) Sn 5. How many lone pairs are in a Lewis dot diagram of CH 4? (A) 0 (B) 1 (C) 2 (D) 4 6. The correct formula for barium chloride is: (A) BaCl (B) BaCl 2 (C) Ba 2 Cl (D) BaCl 7 7. Which of the following will NOT form? (A) Na 2 O (B) Mg 2 Na (C) NaF (D) AlCl 3 8. The shape of an NH 3 molecule is (A) tetrahedral (B) pyramidal (C) bent (D) linear 9. The shape of a molecule is determined because (A) electron domains like to be as far apart from each other as possible (B) electron domains like to be as close to each other as possible (C) electron domains attract each other (D) electron domains have to be at 90 o angles from each other 10. In a nonpolar covalent bond, the electrons (A) are shared equally (C) are not shared at all (B) are shared unequally (D) are not involved in bonding 11. The correct way to represent a solution of copper sulfate is (A) Cu (s) (B) Cu (aq) (C) CuSO 4 (aq) (D) CuSO 4 (s) 12. Which scientist discovered the electron and proposed the plum pudding model of the atom? (A) Dalton (B) Rutherford (C) Bohr (D) Thomson

2 13. MgBr 2 (s) is an example of (A) a solution (C) a compound (B) an element (D) a mixture 14. What piece of lab equipment would you use to accurately measure the volume of a liquid? (A) beaker (B) test tube (C) graduated cylinder (D) hot plate 15. A metal sample has a mass of 38.9 grams. If it is pure solid iron, what should the volume be? (The density of solid iron is 7.78 g/ml.) (A) 31.1 ml (C) 0.20 ml (B) 5.0 ml (D) There is no relationship between mass and volume. 16. In what phase must a molecule be in order for it to be smelled? (A) solid (B) liquid (C) gas (D) aqueous 17. The least reactive group of elements on the periodic table is the A) alkali metals. B) halogens. C) noble gases. D) transition metals. 18. When an ion is created, the number of are changed in the atom. A) protons B) electrons C) neutrons D) alpha particles 19. The picture to the right is which type of representation of a molecule? A) structural formula B) Lewis dot diagram C) molecular formula D) ball and stick model 20. How many bonds should a hydrogen atom form? A) 0 B) 1 C) 2 D) 3 Use this information to answer Questions , Carbon 12

3 , Carbon 13, Carbon What is different about the three different isotopes shown? A. the number of electrons B. the number of neutrons C. the number of nuclei D. the number of protons 22. In the isotope symbols shown above, what does the number on the left above the C represent? A. atomic number B. number of protons C. number of neutrons D. mass number 23. Dinitrogen monoxide is a a. covalent compound b. ionic compound c. metallic compound d. none of the above 24. Structural isomers are a. Compounds with the same molecular formulas but different structural formulas b. Compounds with the same molecular and structural formulas c. Compounds with different molecular formulas and structural formulas d. Compounds with different molecular formulas but the same structural formulas 25. The correct name of B 5 H 9 is a. boron hydride b. pentaboron hydride c. pentaboron nonahydride d. boron nonahydride

4 Open Response Questions 1. CBr 4 and NaBr are two compounds formed differently on the molecular level. a. Identify the type of bond formed in each compound CBr 4 contains covalent bonds while NaBr contains ionic bonds b. Compare and contrast the two types of bonds. Include at least two similarities and two differences between them. Similarities: both types of bonds involve electrons. Both also result in the formation of compounds from two or more elements. However, ionic bonds involve complete transfer of electrons while in covalent bonds, the electrons are shared. Also, ionic bonds involve metals and nonmetals, while covalent bonds only involve nonmetals. 2. Imagine that you found two gold colored rods of different volumes in a laboratory stockroom. Rod A has a mass of 28.3 g and Rod B has a mass of 14.0g. Describe the procedures (experiment) that you would complete to determine whether or not the two gold rods are made of the same metal. Include the lab materials you would need to use and how you would use them. For this experiment, I would need water, graduated cylinders, and the metal rods. I would first measure the volume of the rods using water displacement: I would take the initial volume of water using a graduated cylinder and then take the final volume after placing the metal rod n the graduated cylinders of water. The difference between the initial and final volumes of water would be the volume of the rods. Using these volumes and the masses given, I would calculate density by dividing mass by volume. I would then compare the densities of the two rods to see if they are made of the same materials since density is an intrinsic property, and each substance has its own unique density. 3. Sodium has an atomic number of 11 and a mass number of 23. a. Identify the types of subatomic particles located in the nucleus of a sodium atom. Compare the properties of each type of particle. Protons: positively charged particles Neutrons: neutral particles b. Where is most of a sodium atom s mass located? Explain your answer. Most of the mass of sodium is located in the nucleus. Protons and neutrons contribute to the mass of an atom, while electrons do not. c. Identify the subatomic particles that are found in the energy levels outside the nucleus of a sodium atom. Describe the number and arrangement of these particles. Electrons are found in the energy levels outside of the nucleus. A neutral atom of sodium has a total of 11 electrons. There are 2 electrons in the first shell, 8 in the second shell, and 1 in the valence shell d. Explain the role of electrons in a chemical reaction between atoms of two different elements. Atoms form bonds to other atoms using their valence electrons. In the case of sodium, it would lose an electron to a nonmetal in order to have a full valence electron shell like Neon. 4. An atom has an atomic mass of 14amu. The atom has 5 neutrons a) What is the identity of this element? How do you know? (show your calculations) mass # of neutrons = # of protons = atomic number. # of protons determines the identity of an atom. 14 5=9. This element is fluorine (F) which has an atomic number of 9 b) Write the isotope symbol of this element 14 F 9

5 c) This atom exists in a neutral state. How many electrons does it contain? How do you know? 9 electrons. In a neutral atom, the number of protons = the number of electrons d) Draw a model of this atom *on your diagram, be sure to indicate the numbe of protons and neutrons in the nucleus e) Many of the atomic masses in your periodic table contain a decimal. The mass number above (14 amu) is a whole number (it does not contain a decimal). Explain why. The atomic masses in the periodic table are a weighted average of all the masses numbers of the different isotopes of an element. The mass number above, 14 amu, is a whole number because it is the mass of a single atom of fluorine, which is obtained by adding the total number of protons to the total number of neutrons in this atom of fluorine. Write the names of the following compounds (questions 5 9): 5. SO 2 sulfur dioxide 6. N 2 O 2 dinitrogen dioxide 9. CuCO 3 copper carbonate 8. Fe O 2 3 iron (III) oxide Write the chemical formula for the following compounds (questions 11 16): 11. iron (III) oxide Fe 2 O copper (II) nitrate Cu(NO 3 ) sodium nitride Na 3 N 14. potassium fluoride KF 15. silicon tetrafluoride SiF nitrogen dioxide NO a. Draw a picture of two water molecules hydrogen bonding. Show the partial charges on the molecules.

6 b. Explain how hydrogen bonding affects the evaporation rate of water compared to molecules that do not hydrogen bond? Hydrogen bonding is the strongest of the intermolecular forces. It makes water molecules stick to each other. Therefore, water evaporates more slowly than molecules that do not form hydrogen bonds because in order for water to evaporate, that is in order for water molecules to be separated from each other so that some molecules can escape in the gas form into the surroundings, more energy is required to break the very strong hydrogen bonds making the water molecules stick to each other. 18. Consider the following equation NaCN + H 2 SO 4 Na 2 SO 4 + HCN a. What are the reactants? The reactannts are NaCN and H 2 SO 4 b. What are the products? The products are HCN and Na 2 SO 4 c. How can you tell if the reaction is balanced or not? In order to know whether or not the reaction s balance, I have to count each element to make sure that there are equal numbers of atoms of each elements on the reactant side as there are on the product side. d. Balance the equation. Use a chart. 2 NaCN + H 2 SO 4 Na 2 SO 4 + 2HCN e. Classify the reaction as combination/synthesis, decomposition, single replacement or double replacement. Explain your reasoning. This is a double replacement reaction because Na and H switched partners. Na started out with CN and ended up with SO 4, while H started out with SO 4 and ended up with CN 19. i) Write and balance the following word equations. Use a chart! a. iron + oxygen iron (III) oxide 4Fe + 3O 2 2Fe 2 O 3 b. iron (II) sulfate + sodium hydroxide iron (II) hydroxide + sodium sulfate FeSO 4 + 2NaOH Fe(OH) 2 + Na 2 SO 4 ii) Classify each reaction as combination/synthesis, decomposition, single replacement or double replacement. Explain your reasoning. Reaction (a) is a synthesis/combination reaction because we started out with two elements on the reactant side and ended up with one compound on the product side. Reaction (b) is a double replacement reaction because iron and sodium switched partners/anions during the reaction.