Name _________________________________________
Gen Chem I Lecture
| Exam 2 | 10OCT97 | Dr. L. J. Rivela |
| 1. | The specific heat of iron metal is 0.476 J / g°C. It is found that 48.6 cal must be absorbed by a mass of iron in order to raise its temperature from 26.00 to 31.46 °C. Calculate the mass of the iron. [10] |
| 2. | For the following nuclide determine . . . 238 [U] +3 [10] |
| # electrons ________ | # neutrons ________ | # protons ________ | mass # ________ | |
| atomic # ________ | # nucleons ________ | charge of species ________ |
| 3. | Please clearly state the Law of Definite Proportions . [8] |
| _______________________________________________________________________________ | |
| _______________________________________________________________________________ | |
| Please clearly state the Law of Multiple Proportions. | |
| _______________________________________________________________________________ | |
| _______________________________________________________________________________ |
| 4. | [a] | Please give an isotope of 32 P | _____________________________________ |
| [b] | Please give an isobar of 45 Sc | _____________________________________ | |
| [10] | [c] | Alpha radiation consists of | _____________________________________ |
| [d] | 14 C will emit beta radiation, write a balanced nuclear equation for this process | _____________________________________ |
| 5. | Please balance the following equations. Supply all coefficients . . . even a " 1 " [12] |
| [a] | XeF6 + H2O | --> XeO3 + HF | |
| [b] | SrCl2 + Na3PO4 | --> Sr3(PO4)2 + NaCl | |
| [c] | C5H9N2O + O2 | --> CO2 + H2O + N2O3 | |
| [d] | Fe3O4 + C + Br2 | --> FeBr3 + CO |
| 6. | Please write the proper nomenclature (names) based on the following formulas or write [16] the proper formula based upon the following names: PROPER SPELLING IS ESSENTIAL [16] |
| [a] | sodium phosphate | __________________ | [e] | HClO3 | ________________________ | |
| [b] | chlorite ion | __________________ | [f] | NO2 | ________________________ | |
| [c] | magnesium nitride | __________________ | [g] | NH4Br | ________________________ | |
| [d] | calcium hydroxide | __________________ | [h] | V2(SO4)5 | ________________________ |
| 7. | Determine the mass of K3FeBr6 that is equivalent to in 7.65 x10-2 mole of K3FeBr6 ? [6] |
| 8. | Please briefly and clearly indicate the MAJOR CONTRIBUTIONS that each of the following classic experiments made to the scientific community. [12] |
| [a] | Millikan's Experiment | ____________________________________________________ | |
| [b] | Moseley's Experiment | ____________________________________________________ | |
| [c] | Goldstein's Experiment | ____________________________________________________ | |
| [d] | Thomson's Experiment | ____________________________________________________ |
| 9. | The molecular weight of hemoglobin is about 65,000 g/mol. Hemoglobin contains 0 .35% Fe by mass. How many iron atoms are in a hemoglobin molecule? [8] |
| 10. | Please consider the Cathode Ray Experiment. [10] |
| [a] | draw a well-labeled diagram of the Crooks tube apparatus used in this experiment. |
| [b] | indicate the observations obtained in this experiment. |
| 11. | An unknown element is a mixture of three isotopes. Isotope A has a mass of 228.934 amu and a percent abundance of 25.000. Isotope B and Isotope C have masses of 230.976 amu and 235.988 amu, respectively. The average atomic weight of the unknown element is231.182 amu. Determine the percent abundance of Isotope C. [12] |
| 12. | A sample of "KING'S GOLD", an arsenic - sulfur compound, contains 39.100 % S by mass. Calculate the empirical formula of this compound. [10] |
| 13. | A compound has an empirical formula of S2Cl2O3 . The molecular weight of this compound is found to be 955 g / mol. What is the true or molecular formula of this compound ? [5] |
| 14. | A chemical compound is known to contain only titanium and bromine. A 13.680 gram sample of this compound was chemical reacted and 25.154 g of PbBr 2 was produced. What is the percent composition of this compound ? [10] |
| 15. | Clearly distinguish between an ionic substance and a molecular substance. [6] |
| 16. | Please define the following terms in Short, Concise Statements. [8] |
| Reaction Stoichiometry | __________________________________________________ | |
| __________________________________________________ | ||
| Mole | __________________________________________________ | |
| __________________________________________________ | ||
| 17. | After the discovery of alpha particles, Hans Geiger and Ernest Marsden, working in Ernest Rutherford's laboratory, observed the effect of bombarding thin metal foils with alpha particles. Please indicate the conclusions of this exciting experiment. [10] |
| Extra Credit . . . if you like |
| Three samples of magnesium
oxide were analyzed to determine the mass ratios of O / Mg, to give the following results: |
| 1.60 g O / 2.43 g Mg | 3.83 g O / 5.82 g Mg | 2.29 g O / 3.48 g Mg |
| Show by calculation which
law of chemical combination is illustrated by these data and state the law. [8] |
Total points = 160