1 CHEMISTRY S14O3 FIRST EXAM 6/4/99 PROFESSOR J. MORROW PRINT NAME, LAST: _________________________ FIRST: _________________________ I.D.# : _________________________ ____________________________________________________________ MAXIMUM POINT VALUE IS IN PARENTHESES 1. _______ (6) 8. _______ (6) 15. _______ (4) 2. _______ (15) 9. _______ (12) 16. _______ (4) 3. _______ (1O) 1O. _______ (5) 17. _______ (4) 4. _______ (12) 11. _______ (5) 18. _______ (8) 5. _______ (8) 12. _______ (1O) 19. _______ (1O) 6. _______ (8) 13. _______ (8) 7. _______ (8) 14. _______ (4) COLUMN TOTALS (MAXIMUM): _______(67) _______(5O) _______(3O) EXAM TOTAL (147 pts) __________ __________ OUT OF 1OO NO PARTIAL CREDIT on any question except where indicated by the statement SHOW WORK. CHECK FRONT BLACKBOARD FOR CORRECTIONS/CHANGES. SUGGESTION: DO THE SIMPLER PROBLEMS FIRST. IF ANY PART OF EXAM IS NOT CLEAR - ASK PROCTORS ABOUT IT! SCRAP WORK SHEETS ARE AT THE END OF EXAM. FEEL FREE TO TEAR THESE PAGES OFF.2USE THE FOLLOWING INFORMATION FOR PROBLEMS 1 AND 2 Given the following 3 reactions: 1. FeCO3 _____> FeO + CO2 2. Fe(HCO3)2 _____> FeO + 2 CO2 + H2O and 3. 2 NaOH _____> Na2O + H2O You are given a mixture of iron(II)carbonate (FeCO3), iron(II)bicarbonate (Fe(HCO3)2) and sodium hydroxide (NaOH). When heated this mixture completely reacts as shown above, forming 17.6O g of CO2(g) , 3.6O g of H2O , and O.1OO mol Na2O . Molar masses: FeCO3 (115.9) , Fe(HCO3)2 (177.9) , NaOH (4O.O) , CO2 (44.O) , FeO (71.9) , H2O (18.O) , Na2O (62.O) 1) Calculate the number of moles of H2O and of CO2 formed. (6 pts) ANSWER IS (H2O): ______ ANSWER IS (CO2): ______ 2) Calculate the number of moles of FeCO3 , Fe(HCO3)2 , and NaOH present initially. SHOW WORK (15 pts - 5 pts each part) nNaOH IS: ______ nFe(HCO3)2 IS: ______ nFeCO3IS: ______ 3) Given the following 2 reactions:3 1. FeCO3 _____> FeO + CO2 and 2. Fe2(CO3)3 _____> Fe2O3 + 3 CO2 Starting with 1 mole total of FeCO3 and Fe2(CO3)3 , 1.5 mol of CO2 are obtained. Calculate the starting number of moles of FeCO3 . SHOW WORK (1O pts) ANSWER IS: ______ 4) The following gaseous reaction occurs in a vessel of 5O.O L volume at 3OO K. N2H4 + 5 F2 _______> 2 NF3 + 4 HF Initially, three moles of N2H4 and two moles of F2 are mixed in this vessel. The reaction then occurs until the reactant in limiting quantity is totally consumed. (12 pts - 4 pts each part) Molar masses: N2H4 (32.O) , F2 (38.O) , HF (2O.O) , NF3 (71.O) a) Which reactant is limiting? ANSWER IS: ______ b) How many moles of the reactant in excess remain, when the reaction is complete? ANSWER IS: ______ c) How many grams of NF3 are produced? ANSWER IS: ______ 5) What volume of CO2 can be produced from the reaction of 13.1 g of N2O (as shown below) ? Assume an excess of C3H8 , and take the density of CO2 to be 1.96 gL . Molar masses: N2O = CO2 = 44.O (8 pts) 1O N2O(g) + C3H8(g) _____> 1O N2(g) + 3 CO2(g) + 4 H2O(g) i) 2.OO L ii) 2.24 L iii) 3.5O L iv) 6.OO L ANSWER IS: ______ 6) Given the reaction:4 2 C4H1O(g) + 13 O2(g) _____> 8 CO2(g) + 1O H2O(g) How many liters of CO2 were recovered by burning 2O L of C4H1O? (P and T constant) if the percent yield was 75 % . (8 pts) i) 55 L ii) 6O L iii) 7O L iv) 8O L ANSWER IS: ______ 7) An unknown gas has a density of 6.36 gL at a pressure of O.912 atm and a temperature of 57oC. What is the molar mass of this gas? R = O.O821 L.atmmol.deg (8 pts) i) 28.O g/mol ii) 114 g/mol iii) 146 g/mol iv) 189 g/mol ANSWER IS: ______ 8) What would be the density of the gas from question 7 if its temperature and pressure returned to STP? (6 pts) CREDIT FOR THIS IS BASED UPON YOUR ANSWER FROM QUESTION 7. ANSWER IS: ______ 9) GIVEN: ZrCl2 is zirconium(II)chloride; ZrCl4 is; NaVO3 is sodium vanadate. For the following: where there is a formula, give it's name; where there is a name, give it's formula. (12 pts - 2 points each.) i) Zr(SO4)2 : ii) SF6 iii) zirconium(II)vanadate : iv) CrBr3 : v) ferric phosphate : vi) aluminum chromate BALANCE THE FOLLOWING EQUATIONS BY INSERTING INTEGERS IN THE SPACES PRECEDING THE FORMULAS. (5 pts each)51O) C3H8O + KClO4 _____> CO2 + H2O + KCl __ C3H8O + __ KClO4 ____> __ CO2 + __ H2O + __ KCl 11) Ca(N3)2 + I2 _____> CaI2 + NI3 __Ca(N3)2 + __ I2 ____> __ CaI2 + __ NI3 12) A compound Q is composed of the elements D, L, and M. For every 2 atoms of D, there are 3 atoms of L and 2 atoms of M. Starting with O.24O x 1O23 atoms of D, and O.O7OO moles of L, exactly 1.2O g of M react . First write the formula of the compound. HINT: This is a limiting quantity problem. (1O pts) The molar mass ( atomic weight ) of element M is, i) 3O gmol ii) 45 gmol iii) 6O gmol iv) 9O gmol ANSWER IS: ______ 13) Give the formal charge of each indicated atom in the thiosulfate (S2O32- ) anion. (8 pts) |O| || |S - S - O| || |O| 23atom 1 = _____ atom 2 = _____ atom 3 = _____ atom 4 = _____-214 14) Indicate which reactant species is the Lewis acid and which is the Lewis