1995 - U.S. National Chemistry Olympiad: 1995 Local Test Go...

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U.S. National Chemistry Olympiad: 1995 Local Test Go to Answers 1. Which gas could be collected over water? (A) ammonia (B) carbon dioxide (C) hydrogen chloride (D) oxygen 2. When sodium oxide, Na 2 O, is added to water, the major products expected are (A) Na + and OH¯ ions (B) Na + ions and H 2 O (C) Na + and O 2 ¯ ions (D) Na + and OH¯ ions, and O 2 gas 3. Which metal will react most vigorously with water? (A) Na (B) K (C) Mg (D) Ca 4. When 21.410 g of copper are added to a graduated cylinder containing 12.5 mL of water, the volume rises to 14.9 mL. What is the density of copper? (A) 8.9208 g mL¯ 1 (B) 8.921 g mL¯ 1 (C) 8.92 g mL¯ 1 (D) 8.9 g mL¯ 1 5. Which of these gases is least abundant in the Earth's atmosphere? (A) argon (B) carbon monoxide (C) nitrogen (D) oxygen 6. The percentage of water in a hydrated salt is to be determined by weighing a sample of the hydrate, heating it to drive off the water, and weighing the anhydrous product. Which procedural error(s) could result in a percentage of water that is too low?
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Procedural Mistakes I. not heating the hydrate long enough II. weighing the anhydrous sample while it is still warm III. using a balance tht reads 0.12 g high for both weighings (A) I only (B) II only (C) I and II only (D) I and III only 7. How many grams of Ba(OH) 2 . 8H 2 0 (molar mass = 315.4 g mol¯ 1 ) are needed to prepare 250. mL of solution in which the [OH¯] = 0.180 M? (A) 28.4 (B) 14.2 (C) 7.10 (D) 3.86 8. Ammonia is prepared by the Haber Process. N 2 + 3 H 2 <===> 2 NH 3 If 2 mol of N 2 and 3 mol of H 2 are combined, the amount of NH 3 that would be formed if all of the limiting reactant were used up is known as the (A) limited yield (B) percent yield (C) product yield (D) theoretical yield 9. Calculate the percent by mass of hydrogen in diethylamine, (C 2 H 5 ) 2 NH. (A) 11.3% (B) 13.7% (C) 15.2% (D) 23.6% 10. The insecticide Lindane®, has the emperical formula, CHCl. How many carbon atoms does each Lindane molecule contain? Molar Mass of Lindane = 290.8 g mol¯ 1 (A) 2 (B) 3 (C) 4 (D) 6
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11. 2.0 x 10¯ 3 mol of a chlorine containing compound, when placed in water, reacted completely with 40.0 cm 3 of 0.1 M AgNO 3 . The compound could be (A) NaCl (B) MgCl 2 (C) AlCl 3 (D) TiCl 4 12. Which reaction will produce a precipitate when 0.1 M aqueous solutions are mixed? (A) NaOH + H 2 S ---> (B) CaCl 2 + K 2 CO 3 ---> (C) Al(NO 3 ) 3 + Na 2 SO 4 ---> (D) CuSO 4 + NH 4 Cl ---> 13. What volume of oxygen gas (O 2 ), is measured at 0 °C and 1 atm, is needed to completely burn 1 L of propane (C 3 H 8 ) measured at the same onditions? (A) 10 L (B) 7 L (C) 6 L (D) 5 L 14. The number of moles of KOH in 500 mL of solution to be determined by titrating 10.00 mL portions of the KOH solution with 0.115 M HCl solution. If 18.72 mL of the HCl solution are needed to titrate each 10.00 mL portion of the KOH solution, how many moles of KOH are present in the original solution? (A) 0.00215 mol
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This note was uploaded on 11/09/2011 for the course CHEM 111 taught by Professor Rogers during the Fall '08 term at Thomas Edison State.

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1995 - U.S. National Chemistry Olympiad: 1995 Local Test Go...

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