Midterm Examination 1

Transcription

1 CHEM 121 General Chemistry Summer 2012 Name: Midterm Examination 1 Multiple Choice, etc. 1. The following: The elemental composition of a given compound is always fixed, no matter the method of preparation or isolation. is an example of a: a) Theory. b) Natural Law. c) simple Quantitative Experimental result. d) simple Qualitative Experimental result. 2. Rutherford's Gold Foil Scattering experiment: a) determined the charge on the electron. b) determined the charge on the neutron. c) demonstrated the nuclear structure of the atom. d) demonstrated the existence of the neutron. 3. Perform the following unit conversion: a) 3.87 x 10 2 mg b) 3.87 x 10 4 mg c) 3.87 x 10 6 mg d) 3.87 x 10 8 mg 3.87 ng =? mg 4. Perform the following unit conversion: a) 4.13 x 10 6 km 3 b) 4.13 x 10 9 km 3 c) 4.13 x km 3 d) 4.13 x km cm 3 =? km 3

2 5. The mass standard for atoms is a 12 C atom, which is assigned a mass of 12 amu. What is this mass in terms of the mass standard for ordinary objects, the kilogram? a) 1.57 x kg b) 2.11 x kg c) 1.99 x10 23 kg d) 3.77 x kg 6. The volume of a liquid is measured with a graduated cylinder and is reported as 2.34 ml. This graduated cylinder is graduated (marked) to: a) 1 ml b) 0.1 ml c) 0.01 ml d) ml 7. The difference between the two mass measurements below: g 2.73g will contain how many significant figures? a) 2 b) 3 c) 4 d) 5 8. The compound Plumbous Plumbate is 89.62% Lead and 10.38% Oxygen. How much Oxygen is required to react with 8.00g of Lead? a) 0.57 g. b) 0.79 g. c) 0.93 g. d) 1.23 g.

3 9. Alcohol boils at 78.5 o C. This is: a) a chemical property of Alcohol. b) an extensive physical property of Alcohol. c) an intensive physical property of Alcohol. d) not a characteristic property of Alcohol. 10. SugarWater is an example of a: a) heterogeneous system. b) solution. c) compound. d) (a) and (b). 11. Oil and Vinegar dressing is an example of a: a) heterogeneous system. b) homogeneous system. c) solution. d) compound. 12. Column Chromatography can be used to separate the pigments in the leaves of Spinach. It is found the Carotenoid pigments will move faster along the column than the Chlorophyll pigmennts. This implies: a) the Carotenoids have a higher affinity for the solid support that the Chlorophylls. b) the Chlorophylls have a higher affinity for the eluting solvent than the Carotenoids. c) the Carotenoids have a lower affinity for the eluting solvent than the Chlorophylls. d) the Carotenoids have a lower affinity for the solid support than the Chlorophylls. 13. Elemental Argon (Ar) is a: a) gaseous nonmetal. b) liquid nonmetal. c) liquid metal. d) solid metal.

4 14. Elemental Zirconium (Zr) is a: a) liquid metal of Group 4B. b) solid metal of Group 4B. c) solid nonmetal of Group 4B. d) liquid nonmetal of Group 4B. 15. For the following compound: Ca 3 (PO 4 ) 2 how many atoms of each constituent element is contained in a "molecule" of the compound? Calcium Phosphorus Oxygen 16. Nitrogen reacts with Oxygen to form several different compounds. Two of these are Nitrous Oxide and Nitric Oxide. The chemical formulas of these compounds are: Nitrous Oxide: Nitric Oxide: N 2 O NO If 1.00g of Oxygen is consumed, 1.75g Nitrogen is needed to form Nitrous Oxide. If, again, 1.00g of Oxygen is consumed, how much Nitrogen is required to form Nitric Oxide? a) 1.138g b) 2.112g c) 0.875g d) 0.544g 17. An atom of 75 As contains how many protons? a) 75 b) 99 c) 23 d) 33

5 18. An atom of 51 V contains how many neutrons? a) 51 b) 23 c) 28 d) An atom of S 2 contains how many electrons? a) 16 b) 79 c) 18 d) The mass of an atom is determined primarily by: a) the electrons and protons contained in the atom. b) the neutrons and electrons contained in the atom. c) the neutrons and protons contained in the atom. d) the protons contained in the atom. 21. In rough terms, if an atom were the size of a typical sports stadium, the nucleus is the size of a: 22. The ions 63 Cu + and 63 Cu 2+ differ in their: a) masses. b) numbers of neutrons. c) numbers of protons. d) numbers of electons. 23. Indicate if the following postulates of Dalton's Atomic Theory continue to hold in their entirety; i.e., are True or False. Atoms of a given element are alike. Atoms of different elements differ in their properties, such as mass, volume, etc.

6 24. Provide a name for the following compound: Cr 3 (PO 4 ) What is the chemical formula for Mercuric Chloride?

7 Written Questions 1. Elemental Osmium was first discovered in 1803 as the solid residue left when crude Platinum was dissolved in Aqua Regia. It is a lustrous bluewhite metal that is currently credited with being the heaviest element; although the measured density is in doubt and is very close to that of elemental Iridium. Xray crystallographic measurements suggest the density of metallic Osmium is g/cm 3. a) What is the mass a cube of this metal, reported in grams, whose sides each measure 12 inch on each side? (You must show your work!!!) b) What is the above result when reported in pounds (lb)? (You must show your work!!!) c) What physical quantity does the unit pound (lb) represent, and are you bothered by the calculation being asked of you in part (b) above? Provide an appropriate explanation for your answer.

8 2. After strong heating of 2.500g of the Red Calx of Mercury for several days, 2.315g of elemental Mercury remains. Red Calx of Mercury Mercury + Oxygen a) How much Oxygen is liberated during this reaction? (You must show your work!!!) b) What is the elemental composition (mass percentage) of the Red Calx of Mercury? (You must show your work!!!) 3. Silver has two naturally occurring isotopes. These are 107 Ag ( amu, 51.28%) and 109 Ag ( amu, 48.18%). By direct calculation, determine the atomic weight of naturally occurring Silver. (You must show your work!!!)

9 Appendix Useful Information Unit Conversions Common Polyatomic Ions Acetate CH 3 CO 2 Bicarbonate HCO 3 or C 2 H 3 O 2 Carbonate 2 CO 3 Ammonium + NH 4 Cyanide CN Perchlorate ClO 4 Hydroxide OH Chlorate ClO 3 Oxalate 2 C 2 O 4 Chlorite ClO 2 Permanganate MnO 4 Hypochlorite ClO Nitrate NO 3 Nitrite NO 2 Chromate 2 CrO 4 Dichromate 2 Cr 2 O 7 Bisulfate HSO 4 Sulfate 2 SO 4 Bisulfite HSO 3 Sulfite 2 SO 3 Thiosulfate 2 S 2 O 3 Phosphate 3 PO 4 Hydrogen Phosphate 2 HPO 4 Dihydrogen Phosphate H 2 PO 4

10 Naming Conventions (ide) Endings for the NonMetals Group 4A Group 5A Group 6A Group 7A Carbide Nitride Oxide Fluoride Phosphide Sulfide Chloride Arsenide Selenide Bromide Telluride Iodide Ordering for NonMetal with NonMetal Compounds Element: B Si C Sb As P N H Te Se S I Br Cl O F Group: 3A 4A 5A 6A 7A Greek Prefixes Number one two three four five six seven eight nine ten Prefix monoditritetrapentahexaheptaoctanonadeca Latin Names of the Elements English Name Latin Name Symbol Antimony Stibium Sb Copper Cuprum Cu Gold Aurum Au Iron Ferrum Fe Lead Plumbum Pb Mercury Hydragyrum Hg Potassium Kalium K Silver Argentum Ag Sodium Natrium Na Tin Stannum Sn

11 Fundamental Constants Mass of Electron = x g Mass of Proton = x g Mass of Neutron = x g Fundamental Charge = x C Speed of Light = c = 3 x 10 8 m/sec Planck's Constant = h = x J sec Avogadro's Number = N A = x entities / mole