Answers to Midyear Multiple Choice Practice Problems

January 2004

Answer Notes Answer Notes
1. C This is a metric converstion from milliliters to liters (base unit). 26. B From Boyle's Law, dropping the pressure by 1/2 will double the volume (inverse relationship). From Charles' Law, doubling the absolute temperature will double the volume. In this situation, both are happening ( doubled and doubled again, or 4x)
2. A In scientific notation, all numbers in the mantissa are signficant, even zeroes 27. C The sum of the pressures of the individual gases (a, b, and c) add up to the total pressure - Dalton's Law.
3. A For addition, we round based on the least accurate decimal place - since 12.5 is only known to the 10ths place, we round the answer to the 10ths place. 28. A A is the only one that is a statement of Charles' Law.
4. A Safety Goggles, aways!! The blingbling is up to you. 29. B A, C, and D are not true for ideal gases, which is what the kinetic molecular theory describes.
5. D Make sure you know the element symbols on page 50 in text. 30. A The total moles are 5 moles, and oxygen is 4/5 of the moles. Therefore it will have 4/5 of the total pressure.
6. C Make sure you know the element symbols on page 50 in text. 31. E Celsius is not an absolute temperature scale, so we don't know its effect on volume for sure. The volume will go up, but we don't know how much.
7. D Substances are (only) elements or compounds. A, B, and C apply to both of these. 32. A Density = mass/volume
8. A Endothermic processes take in energy from the surroundings. 33. C You need to know where the transition metals are on the periodic chart. Sodium is not in their part of the chart.
9. E During chemical reactions, new substances are formed, and they have different physcial and chemical properties than the reactants. 34. C Mass number is protons + neutrons. In this question, 12+14 = 26.
10. A Phase changes (boiling, freezing, evaporation, sublimation) are physical changes - they do not change the chemical composition of the substance. 35. E Atomic mass (not to be confused with atomic number, or mass number) is the average mass depending on the naturally occurring abundance. Can't tell this from just one isotope.
11. B Smallest unit of an element is an atom. Smallest unit of a compound is a molecule. 36. D Since only the neutrons are changing, this makes the atom a different isotope (of the same element).
12. A (B should have read "5 g of oxygen") Oxygen atoms are heavier, so 5 g of hydrogen would have more atoms. 37. A The atom has 12 protons, so it has an atomic number of 12, which is magnesium (see a periodic chart).
13. D Substances are (only) elements or compounds. 38. A Currently nuclear power plants use fission. Fusion power is only experimental.
14. B Sodium is in Group I on the periodic chart, and all of these form +1 ions. The rest are in Group IV, and these form -1 ions. 39. C A beta particle, released during beta decay, is a high-speed electron.
15. A You need to know where the metal/nonmetal dividing line is on the periodic chart. 40. F There is no gas law that relates mass to pressure.
16. C Noble gases (also known as the inert gases) do not generally form ions. 41. F None of these are volume units.
17. D Polyatomic ions have a charge and contain more than one atom. 42. F If they are soluble, they will not precipitate!
18. A Make sure you know the naming systems for compounds. Remember that the (II) means that copper has a +2 charge. 43. F Density is an intenstive property.
19. -- There is no correct answer listed. The correct answer would be CF4 (Should this happen on the exam, every student would receive credit for the question). 44. F It may be binary, but it is not nonmetallic. Fe is a metal.
20. D For single replacement reactions, more active elements replace less active elements. A could also be a reaonable answer. 45. F No - the statement is an example of the Law of Definite Proportions.
21. C You need to know how to use a solubility chart (which will be provided for the exam). 46. F Silver atoms are heavier, so equal masses will NOT contain the same number of atoms (the same number of moles would...)
22. B A precipitate typically forms during a double replacement reaction, and the rest stay dissolved in the solution. 47. F The formula contains 6 hydrogen atoms.
23. E You need to know how much of B is present, plus the reaciton equation, to determine the mass of any product. 48. T This is the mass of 1 mole of H2, and one mole will have a volume of 22.4 L at STP.
24. D Equal moles have equal numbers of atoms. 49. T One mole of any gas will occupy 22.4 liters at STP. 2.016 is the mass of one mole (remember hydrogen is diatomic).
25. B B is the definition of a limiting reactant. 50. T During both alpha and beta decay, the original atom changes atomic number and therefore changes to a different element.