Name _________________________________________
Gen Chem I Lecture
| Exam 3 | 7NOV97 | Dr. L. J. Rivela |
| 1. | HCl, HBr, and HI are strong acids. Please supply the name and formula for three (3) other strong acids . . . [14] |
| [1] | _________________________________ | _________________________________ | |
| [2] | _________________________________ | _________________________________ | |
| [3] | _________________________________ | _________________________________ |
| State the solubility rule for sulfates compounds: ________________________________ | |
| _______________________________________________________________________________ | |
| State the solubility rule for phosphates: ______________________________________________ | |
| _______________________________________________________________________________ |
| Give the formula of the four (4) common gases that are formed when ionic compounds are treated with acids (or bases) . . . . . |
| [1] | ______________________________ | [3] | ______________________________ | |
| [2] | ______________________________ | [4] | ______________________________ |
| 2. | The following reaction occurs via metathesis. Please complete and balance the reaction: [5] |
| H2SO4 + Al(OH)3 --> |
| 3. | Write the molecular equation and the net ionic equation for the following metathesis reaction [6] |
| KOH + FeBr3 --> |
| 4. | How would you prepare 950. mL of a 2.85 M HBr solution from a 11.6 M HBr stock solution? |
| Please show a calculation and write a few words to indicate how you would prepare the solution.[10] |
| 5. | A method for sulfur analysis uses the following balanced reaction : |
| 40 H2S + 16 KMnO4 + 24 H2SO4 --> 8 K2SO4 + 5 S8 + MnSO4 + 64 H2O | |
| What volume of 0.456 M KMnO 4 would be required to react, according to this equation, in order to produce 143 grams of sulfur [S 8 ]. [10] |
| 6. | An aqueous (water) solution of calcium hydroxide, Ca(OH)2 [M.W. = 74.1 g/mol], is 27.0 %Ca(OH)2 (on a weigh-weight basis). Calculate the mole fraction of water this solution. [10] |
| 7. | An aqueous (water) solution of glucose, C6H12O6 [M.W. = 180.2 g/mol], is 43.0 % C6H12O6 (on a weigh-weight basis) and has a density of 1.38 g/mL. Calculate the molarity of this solution. [10] |
| 8. | The alcohol in "gasohol", C2H5OH(l), burns in oxygen to produce carbon dioxide gas and liquid water. [25] |
| C2H5OH(l) + O2 (g) --> CO2 (g) + H2O(l) |
| Suppose 158.0 g of C2H 5 OH [MW = 46.07 g/mol] is reacted with 286.0 g of O2 [MW = 32.00 g/mol] and 186.5 g of CO2 [MW = 44.01 g/mol] is isolated. |
| [a] | determine the limiting reagent . . . indicate the proper calculations and write a few sentences. | |
| [b] | calculate the amount of the XS reagent that is in excess | |
| [c] | calculate the theoretical yield of CO2 | |
| [d] | calculate the percentage yield of CO2 | |
| 9. | [a] | Define an exothermic reaction and give a physical change as an example . . . [18] |
| _______________________________________________________________ | ||
| [b] | Define what is meant by a closed system . . . | |
| _______________________________________________________________ | ||
| [c] | The heat of reaction at constant pressure, qp , is directly related to ___________ | |
| [d] | The heat of reaction at constant volume, qv , is directly related to ____________ | |
| [e] | A state function [a property of a system that depends only on its present state | |
| and is completely determined by macroscopic variables such as temperature and | ||
| pressure] is said to be path independent. Please explain . . . | ||
| _______________________________________________________________ | ||
| _______________________________________________________________ | ||
| [f] | A reaction is found to have delta H = 33.5 kJ. This means that this is an reaction. | |
| _______________________________________________________________ |
| 10. | Clearly distinguish between an absorption and an emission spectrum. [6] |
| _____________________________________________________________________________ | |
| _____________________________________________________________________________ | |
| _____________________________________________________________________________ |
| 11. | Use standard enthalpies of formation to calculate the value of _ H for the combustion of the alcohol in "gasohol", C2H5OH(l) : [10] |
| C2H5OH(l) + O2 (g) | --> | CO2 (g) + H2O(l) |
| 12. | Compounds with carbon-carbon
double bonds, such as ethylene, C2H4, add hydrogen in a reaction called hydrogenation. Thus [12] |
| 3 C2H4(g) + 3 H2(g) --> 3 C2H6(g) |
| Calculate the enthalpy, delta H , change for this reaction, using the following data: |
| [1] | 12 CO2(g) + 12 H2O(l) | --> | 6 C2H4(g) + 18 O2(g); | delta H1 = 8406 kJ | |
| [2] | C2H6(g) + 7/2 O2(g) | --> | 2 CO2(g) + 3 H2O(l); | delta H2 = - 1550 kJ | |
| [3] | C(graphite) + 1/2 O2(g) | --> | CO(g); | delta H3 = - 111 kJ | |
| [4] | H2(g) + 1/2 O2(g) | --> | H2O(l); | delta H4 = 286 kJ |
| Extra Credit . . . if you like |
| A bomb type calorimeter is used to measure the heat evolved by the combustion of glucose, C6H12O6. A 3.00-g. sample of glucose is placed in the bomb, which is then filled with oxygen gas under pressure. The bomb is placed in a well-insulated calorimeter vessel that is filled with 1.20 kg of water. The initial temperature of the assembly is 19.00°C. The reaction mixture is ignited by the electrical heating of a wire within the bomb. The reaction causes the temperature of the calorimeter and its contents to increase to 25.50°C. The heat capacity of the calorimeter is 2.21 kJ/°C. Calculate delta E for the combustion of one mole of glucose [i.e. kJ/mol]. [12] |
Total points = 136