U.S. National Chemistry Olympiad: 1991 Local Section TestGo to answers 1. What is the maximum amount of MgCl2that can be prepared from the reaction of 10.0g of HCl with 10.0 of Mg(OH)2? 2 HCl + Mg(OH)2---> MgCl2+ 2 H2O (A) 9.26 g (B) 13.1 g (C) 16.3 g (D) 17.5 g 2. Phenylflouroform contains 57.54% C, 3.45% H, and 39.01% F. Its molecular formula is the same as its simplest formula. How many carbon atoms are in one molecule of Phenyflouroform ? 3. What is the most likely formula for a compound of gallium and sulfur ? 4. A mixture of 2.30 x 1023molecules N2and 4.35 x 1023molecules N2O has a total pressure of 2.00 atm. What is the partial pressure of N2? 5. Which element should have the smallest first ionization energy ? (A) Ca (B) Rb (C) Al
(D) Cl 6. An aqueous solution containing 1.00 mol H2SO4is mixed with an aqueous solution containing 1.00 mol NaOH. The mixture is then evaporated to dryness. What solid remains after evaporation ? 7. Which atom is the smallest ? 8. At room temperature and 1 atm pressure the molecules are farthest apart in 9. What is the net-ionic equation for the reaction of aqueous solutions of BaCl2and K2SO4? (A) Ba2+(aq) + 2Cl¯(aq) + 2K+(aq) + SO42¯(aq) ---> BaSO4(s) + 2K+(aq) + 2Cl¯(aq) (B) Ba2+(aq) + SO42¯(aq) ---> BaSO4(s) (C) K+(aq) + Cl¯(aq) ---> KCl(s) (D) Ba2+(aq) + 2Cl¯(aq) + 2K+(aq) + SO42¯(aq) ---> BaSO4(s) + 2KCl(s) 10. When 80.00 mL of 0.200 M HNO3is added to 120.00 mL of 0.150 M KOH, the reaction HNO3(aq) + KOH(aq) ---> KNO3(aq) + H2O(l) occurs and the resulting solution is 11. Methanol burns in oxygen according to the equation
CH3OH + O2---> CO2+ H2O (unbalanced) What volume of oxygen is required to burn 5.0 L of gaseous methonal measured at the same temperature and pressure ? 12. A 50 g sample of an ideal gas occupies a volume of 3.2 L at 40 °C and exerts a pressure of 2.6 atm. What is its molar mass ? 13. When sodium metal reacts with an excess of water the products are (A) Na2O(s) and H2(g) (B) Na+(aq), OH¯(aq) and H2(g) (C) NaH(s) and O2(g) (D) Na2O2(s) and H2(g) 14. Which is leastimportant in determining the physical behavior of a gas? (A) volume (B) pressure (C) temperature (D) chemical composition
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