Chemistry 3070

Sample questions for Exam II

Note: You may use one card (3x5 max!) with anything written on it. You may also use the inside of your book. You will have one hour to complete the exam.

1. Atoms that have the same atomic number but different numbers of neutrons are
a) radioactive
b) isotopes
c) impossible
d) ions

2. The mass of the electrons in atoms is generally regarded as
a) significant
b) insignificant
c) comparable to the mass of the nucleus
d) unknown

3. The element tin (Sn) occurs naturally as ten isotopes. Each of these isotopes has
a) 50 protons
b) 50 electrons
c) a different number of neutrons
d) all of the above

4. The sum of protons and neutrons in an atom is called the
a) atomic number
b) atomic mass
c) mass number
d) abundance

5. The isotope of the element that contains 6 protons, 6 electrons and 7 neutrons is commonly referred to as is
a) "carbon13"
b)"silicon 14"
c) "nitrogen 14"
d) "carbon 12"

6. Which of the following contains a total of 8 neutrons?
a) ¹²C
b) ¹⁴ C
c) ¹⁸ O
d) ¹⁴ N

7. Which one of the following is most penetrating?
a) alpha particle
b) beta particle
c) gamma ray
d) visible light

8. Which of the following particles has a mass of 4 amu and a charge of 2+?
a) alpha particle
b) electron
c) neutron
d) proton

9. Which type of radioactive emission is very similar to xrays?
a) transmutation
b) alpha particle
c) beta particle
d) gamma ray

10. After three half-lifes, what fraction of the original radioactive isotope remains in a sample?
a) none
b) 1/16
c) 1/8
d) 1/4

11. Radioactive alpha emitters pose the greatest potential health risk when they are
a) unshielded
b) on the skin
c) injested
d) all of the above

12. Which one of the following radioactive isotopes is useful in the investigation of thyroid problems?
a) Uranium 235
b) Barium 120
c) Iodine 131
d) Cesium 145

13. Positron emission tomography (PET) is a
a) therapy for cancer using positrons
b) diagnostic technique for monitoring dynamic processes in the body, such as brain activity
c) device for containing a nuclear fusion reaction
d) mechanism for transmutation of elements

14. Technitium 99^m is a radioisotope used in a variety of diagnostic tests. It has a short half life (6 hr). The advantage of a short half-life for diagnostic purposes is
a) the radioactivity is easier to monitor
b) the radioactivity does not linger in the body
c) the radioactivity lasts for a long time
d) the chemical reactions induced by the technitium are more rapid

15. In carbon14 dating
a) the radioactivity of carbon is artificially induced
b) the radioactivity of carbon occurs naturally
c) radioactive carbon is added to the sample to be dated
d) none of the above

16. A piece of fossilized wood has a carbon14 radioactivity that is 1/4 that of new wood. The halflife of carbon14 is 5730 years. How old is the fossilized wood?
a) 1 x 5730 = 5730 years
b) 2 x 5730 = 11,460 years
c) 3 x 5730 = 17,190 years
d) 0.25 x 5730 = 1432 years

17. In the famous relationship: E = mc², the symbol E represents
a) electricity
b) energy
c) electrons
d) speed of light

18. Which scientist won a Nobel prize for chemistry in recognition of his work involving the structure of proteins, and the Nobel prize for peace for his efforts in controlling nuclear weapons?
a) Albert Einstein
b) Linus Pauling
c) Enrico Fermi
d) Glenn Seaborg

19. The original source of essentially all of the energy on the earth is
a) plants
b) oil
c) coal
d) the sun

20. The noble gases are inert. This means they
a) do not react with other elements
b) exist as gases at room temperature
c) undergo many chemical reactions
d) lose and gain electrons easily

21. The inertness of the noble gases is due to
a) the unique structure of their nuclei
b) the special number of protons and neutrons
c) the bonds they form with other elements
d) the number and arrangement of their electrons

22. A sodium ion, Na⁺, has the same electron configuration as a(n)
a) sodium atom
b) chlorine atom
c) neon atom
d) argon atom

23. A chloride ion, Cl^-, has the same electron configuration as a
a) sodium atom
b) chlorine atom
c) neon atom
d) argon atom

24. The number of electrons in a chloride ion, Cl^-, is
a) 16
b) 17
c) 18
d) 35

25. The number of protons in a chloride ion, Cl^-, is
a) 16
b) 17
c) 18
d) 35

26. From the periodic table, the number of valence electrons for most of the main group elements may be determined directly from the periodic table by looking at
a) the atomic number
b) group number which is located at the top of each column
c) period number
d) mass number which is located beneath each element

27. Draw the electron dot formulas for Mg.

28. Draw the electron dot formulas for S.

29. A calcium ion is
a) Ca⁺
b) Ca²⁺
c) Ca
d) Ca^2-

30. An oxide ion is
a) O⁺
b) O²⁺
c) O^2-
d) O₂

31. Aluminum forms ions with a charge of
a) 1+
b) 2+
c) 3+
d) 3

32. Calcium reacts with chlorine to form calcium chloride and the formula is
a) CaCl
b) CaCl₂
c) Ca₂Cl
d) Ca₂Cl₃

33. Magnesium reacts with oxygen to form
a) MgO
b) Mg₂O
c) Mg₂O
d) Mg₃O₂

34. Sodium reacts with chlorine to form
a) NaCl
b) Na₂Cl
c) NaCl₂
d) Na₂Cl₃

35. A covalent bond is formed when a pair of electrons is
a) transferred
b) shared
c) split
d) destroyed

36. Hydrogen is a diatomic molecule, H₂. The bond holding the hydrogen atoms together is
a) ionic
b) nonpolar covalent
c) polar covalent
d) metallic

37. In a nonpolar covalent bond, electrons are
a) shared equally
b) shared unequally
c) transferred
d) uncharged

38. Which one of the following has the HIGHEST electronegativity?
a) fluorine
b) oxygen
c) chlorine
d) sodium

39. In the hydrogen chloride molecule, HCl, the chlorine end of the molecule is more negative than the hydrogen end because
a) chlorine is more electronegative than hydrogen
b) hydrogen is more electronegative than chlorine
c) hydrogen and chlorine have the same electronegativity
d) hydrogen transfers an electron to chlorine

40. Which substance has nonpolar covalent bonds?
a) H₂O
b) NO₂
c) Cl₂
d) CO

41. Which substance has polar covalent bonds and is present in vinegar?
a) CH₄
b)CH₃COOH
c)CCl₄
d)none of the above

42. Which substance has polar covalent bonds?
a) CO₂
b) N₂
c) Cl₂
d) CaO

43. Atoms and molecules with unpaired electrons are called
a) ions
b) odd
c) covalent
d) free radicals

44. The temperature at which a solid becomes a liquid is called the
a) melting point
b) boiling point
c) condensation point
d) decomposition point

45. The temperature at which a liquid becomes a gas is called the
a) melting point
b) boiling point
c) condensation point
d) decomposition point

46. Which physical state is most highly ordered?
a) gas
b) liquid
c) solid
d) all are the same

47. Which of the following ranks the three states of matter from most to least ordered?
a) gas > liquid > solid
b) gas > solid > liquid
c) solid > gas > liquid
d) solid > liquid > gas

48. What is Avogadro's number?
a) 6.02 x 10^-23
b) 6.02 x 10²³
c) 3.02 x 10²⁶
d) 2.06 x 10^-32

Please put your answers to the following questions in the essay section of your answer sheet. (5 points each)
49. Chalk is composed of primarily calcium carbonate. What is the formula of calcium carbonate?

50. Balance the equation for the combustion of octane (C₈H₁₈ )

C₈H₁₈ + O₂ ---------------> CO₂ + H₂O

51. Aspirin has a formula C₉H₈O₄. What is the molar mass of aspirin?

52. In the reaction
CH₄ + 2 O₂ ----------> CO₂ + 2 H₂O,
how many grams of oxygen are required to burn 8.0 g of methane?

53.   In the reaction

C₃H₈ + 5 O₂ ----------> 3 CO₂ +  4 H₂O,
If 5 grams of propane (C₃H₈)are burned, how many grams of carbon dioxide are produced?

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