Test 2 Pre-Test

1. Test 2 Pre-Test OBJECTIVE: Administer this Practice Test 2 & thoroughly explain all incorrect answers. Grade: «grade» Test 2 - Ch 2-9 Subject: «date» Date:

2. EXPLANATION 1 Fluorine belongs to group 7A. How many covalent bonds are formed between two fluorine atoms? you have to do the Lewis Structure A 1 B 2 C 3 D 4

3. EXPLANATION 2 Molecules containing only polar covalent bonds ____. A are always polar B may or may not be polar not polar because it is symmetrical. All atoms on central atom are the same C are always ionic D are always nonpolar Blue atom made this tetrahedral shape polar because of symmetry

4. EXPLANATION 3 How many electrons can occupy a single molecular orbital? All orbitals can only handle a maximum of 2 electrons. A 0 B 1 C 2 D 4

5. EXPLANATION 4 What are shared in a covalent bond? the word covalent means that electrons are being shared by 2 atoms, and not removed from one to the other. A ions B Lewis Structures C electrons D dipoles

6. EXPLANATION 5 What is the correct Lewis structure for hydrogen chloride, HCl? Use my rules for figure out Lewis Structures, get total valence electrons, the use exceptions and octet rule to pass out electrons, then be sure the total valence electrons are there in the Lewis Str, no more, no less. Also see my vids on YouTube A a B b C c D d

7. EXPLANATION 6 The symbol mm represents mm is a definition found in Ch 2 p. 26, combining milli- prefix the base unit meter. A micrometer B millimeter C milliliter D meter

8. EXPLANATION 7 Which of the following represents a compound? molecules of a compound have at least 2 different kinds of atoms A H B H-3 C H2O D O-16

9. EXPLANATION 8 Emission of light from an atom occurs when an electron ____. electron is excited by energy from outside atom (jumps to higher energy level), the light is given off (photon) when it drops back to its ground state A drops from a higher to a lower energy level B jumps from a lower to a higher energy level C moves within its atomic orbital D falls into the nucleus

10. EXPLANATION 9 Trends in the properties of elements in a group or period can be explained in terms of outer shell electrons (valence) determine ratios with which atoms combine to make molecules A binding energy B atomic number C electron configuration D electron affinity

11. EXPLANATION 10 How many electrons are shared in a double covalent bond? each covalent bond is a "stick" and double = 2 A none B one C two D four

12. EXPLANATION 11 When a stable covalent bond forms, the potential energy of the atoms: distance betwee, atoms A increases energy increases B decreases C remains constant lowest possible energy level is a set distance between 2 atoms in a bond. This graph shows relative energy of atoms as they move closer together D becomes zero See ChemThink Tutorial on Chemical Bonding - screen 15

13. 12 A substance that forms a vapor is generally in what physical state at room temperature? EXPLANATION A solid all substances have 3 states - solid, liquid & gas. This question is asking what is the original state of a substance that can be changed into a gas. B liquid C gas D liquid or solid

14. EXPLANATION 13 Which of the following measurements (of different masses) is the most accurate? The amount of accuracy a number shows is determined by the number of sig figs in the number. A 3.1000 g B 3.100 g C 3.122 22 g D 3.000 000 g

15. EXPLANATION 14 In which of the following pair is the second particle listed larger than the first? A K, Ga B Pb, C Relative sizes of two different atoms can be determined by use the trend for size. C Br, Br- D Li, Li+ Positive ions are smaller than the atoms they started out as. Negative ions are larger than the atoms they started out as.

16. EXPLANATION 15 What is the formula for sodium sulfate? A NaSO4 B Na2SO4 C Na(SO4)2 Overall net charge on all molecules must be zero. If not, they will be consider ions D Na2(SO4)2

17. EXPLANATION 16 The shape of a molecule that has two covalent single bonds and no lone pairs on the central atom is ____. covalent bond no unshared pairs covalent bond A tetrahedral B trigonal planar C trigonal pyramidal D linear Presence of unshared pair on this molecule and the shape it represents, rules it out as a possible answer.

18. EXPLANATION Diatomic column 17 nitrogen oxygen hydrogen 17 Which of the following elements can form diatomic molecules held together by triple covalent bonds? A carbon B oxygen C fluorine D nitrogen

19. EXPLANATION 18 A mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together is called a(n) chemical bond (c) look at ChemThink tutorial for Chemical Bonding A dipole B Lewis structure C chemical bond D London force

20. EXPLANATION 19 The substance whose Lewis structure shows three covalent bonds is A H2O B CH2Cl2 C NH3 D CCl4

21. EXPLANATION 20 What must occur for a change to be a chemical reaction? see Ch 3 on chem vs physical changes A There must be a change in chemical properties. B There must be a change in physical properties. C The change must involve a change in mass. D The change must involve a change in volume.

22. EXPLANATION 21 As it travels through space, electromagnetic radiation See Ch 5 on light, p. 118 re wave and p. 122 re particle A exhibits wavelike behavior B loses energy C varies in speed D releases photons

23. EXPLANATION 22 What is the formula for the compound formed by lead(II) ions and chromate ions? roman numerals after the name of a metal tell you the charge on a metal that can have more than one charge. A PbCrO4 So "lead (II)" means that the ion of lead (the metal) has a 2+ charge B Pb2CrO4 C Pb2(CrO4)3 D Pb(CrO4)2 Charges on Pb and Chromate are equal, so we only need one of each.

24. P1 P2 P3 P6 P5 2012-2013 P2 P1 P3 2011-2012 P1 P2 P3 P6 P4 2010-2011