1. The half-life of carbon-14 is approximately 5,700 years; how much of an initial 1 gram sample of carbon-14 will remain after 17,100 years (3 half-lives)? 1.0.5 grams (50%) 2.0.33 grams (33%) 3.0.25 grams (25%) 4.0.125 grams (12.5%) 5.0.0625 grams (6.25%) 12345

2. Buffer systems stabilize what in cells? 1.oxygen concentration 2.pH 3.temperature 4.salt concentration 5.carbon dioxide concentration 12345

3. A glass of grapefruit juice, at pH 3, contains ________ hydrogen ion as a glass of tomato juice, at pH 4. 1.one-tenth as much 2.half as much 3.twice as much 4.three times as much 5.ten times as much 12345

4. An atom has 19 protons, 19 electrons, and 20 neutrons; what is its atomic mass number? 1.19 2.20 3.38 4.39 5.58 12345

5. Using the term orbital to describe the position of an electron is ________. 1.somewhat misleading; the electron is actually somewhere within a particular volume of space 2.appropriate; electron position can be as precisely determined as that of the moon in its orbit 3.appropriate because each atom is like a tiny solar system with an electron like a planet 4.somewhat misleading; electrons oscillate up and down rather than move in circular orbits 5.somewhat misleading; atoms are more like galaxies than solar systems 12345

6. The interactions that occur between water molecules are called ________ bonds. 1.hydrogen 2.nonpolar covalent 3.polar covalent 4.ionic 5.water 12345

7. The most common form of carbon atom has 6 protons, 6 electrons, and 6 neutrons; which combination of subatomic particles would represent a different isotope of carbon? 1.8 protons, 6 electrons, 6 neutrons 2.6 protons, 8 electrons, 6 neutrons 3.8 protons, 8 electrons, 8 neutrons 4.6 protons, 6 electrons, 8 neutrons 5.5 protons, 6 electrons, 6 neutrons 12345

8. Covalent bonds are formed when ________. 1.an atom gains one or more electrons 2.two atoms share one or more pairs of electrons 3.an atom donates one or more electrons to another atom 4.an atom gains or loses one or more protons 5.a positively charged ion and a negatively charged ion associate with each other 12345

9. Oxygen, with an atomic number of 8, would have ________ electrons in the first electron shell and ________ electrons in the second electron shell. 1.1, 7 2.2, 6 3.3, 5 4.4, 4 5.5, 3 12345

10. In a chemical formula, 2H would be used to represent ________. 1.2 atoms of hydrogen 2.2 molecules of hydrogen 3.a single molecule of hydrogen gas 4.a buffer molecule 5.a hydrogen atom capable of forming a double covalent bond 12345

11. In living organisms, the molecule most associated with temperature stability is ________. 1.molecular oxygen 2.sugar 3.hemoglobin 4.sodium chloride 5.water 12345

12. Rank the following chemical bonds from weakest to strongest. 1.covalent, ionic, hydrogen 2.hydrogen, covalent, ionic 3.ionic, hydrogen, covalent 4.hydrogen, ionic, covalent 5.ionic, covalent, hydrogen 12345

13. Which of the following is not a compound? 1.table salt (sodium chloride) 2.carbon 3.water 4.methane 5.glucose 12345

14. Rain has a pH of approximately 6; which of the following terms correctly describes it? 1.alkaline 2.basic 3.acidic 4.neutral 5.polar 12345

15. Calcium, when written as Ca 2+, represents ________. 1.molecular calcium 2.elemental calcium 3.calcium ion 4.a calcium free radical 5.one of the several calcium isotopes 12345

16. A(n) ________ is created when two or more ________ are combined. 1.ion, atoms 2.reactant, products 3.atom, molecules 4.product, reactants 5.atom, ions 12345

17. Which selection represents the breakdown of the water molecule? 12345 1.H 2 O - > H + + 2 O- 2.H 2 O - > H 2 + O 2 - 3.H 2 O - > H + + OH- 4.H 2 O - > 2 H + + O 2 - 5.H 2 O - > O 2 H

18. How many atoms would be present in a single molecule of Na 2 SO 4 ? 1.4 2.5 3.6 4.7 5.8 12345

19. How does a salt differ from an acid? 1.no difference, salt and acid are interchangeable terms 2.both dissolve in water but salts release ions other than H + and OH - 3.acids release H + and salts release OH - when dissolved in water 4.salts are crystallized when dry, while acids are always liquids 5.salts are always products of chemical reactions, while acids are always reactants 12345

20. In solution, hydration spheres will form around ________. 1.any nonpolar solute 2.any solute that can dissolve in water 3.all molecules that are smaller than water 4.all molecules that are larger than water 5.only those solutes dissolved in salt water 12345