1999 - U.S. National Chemistry Olympiad: 1999 Local Section...

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U.S. National Chemistry Olympiad: 1999 Local Section Test Go to the answers 1. Which oxide forms a basic solution when mixed with water? (A) K 2 O (B) Al 2 O 3 (C) CO 2 (D) SO 3 2. Which of these compounds is not white? 1. KMnO 4 2. ZnSO 4 3. FeCl 3 (A) 1 only (B) 1 and 3 only (C) 2 and 3 only (D) 1, 2, and 3 3. Which gas will cause a solution containing potassium iodide and starch to turn a blue-black color? (A) H 2 (B) CO 2 (C) Cl 2 (D) NH 3 4. A colorless aqueous solution contains a single ionic compound. Use this experimental information to deduce the identity of the compound. * When a small amount of dilute NaOH solution is added to the solution, a precipitate forms. This precipitate dissolves when excess NaOH is added. * Addition of AgC 2 H 3 O 2 to the solution gives a white precipitate. (A) AlCl 3 (B) Ba(NO 3 ) 2 (C) CuSO 4 (D) FeI 2 5. The most active metals on the periodic table have
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(A) large radii and high electronegativities. (B) small radii and low electronegativities. (C) small radii and low ionization energies. (D) large radii and low ionization energies. 6. The aqueous solubilities of several compounds between temperatures of 0 °C and 80 °C are shown in this diagram. Which compound can be recovered with the highest percent yield by dissolving a sample in water at 80 °C and cooling to 0 °C? (A) A (B) B (C) C (D) D 7. A student determines the concentration of a solution of NaOH. She pipets a sample of the NaOH solution into a flask and adds two drops of an indicator. Standardized acid is added from a buret until the indicator changes color. Which device may contain residual water without affecting the results of the titration? 1. buret 2. flask 3. pipet (A) 1 only (B) 2 only (C) 1 and 3 only (D) 2 and 3 only 8. The density of a block of metal is determined by weighing it, then submerging it in water. Based on these data, to how many significant figures should the density be reported? Data mass of block 25.472 g
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2 O 10.5 mL volume of H 2 O with block 20.0 mL (A) 2 (B) 3 (C) 4 (D) 5 9. Arsenic(III) sulfide reacts with oxygen to form arsenic(III) oxide and sulfur(IV) oxide as represented by this equation. __As 2 S 3 + __O 2 ---> __As 2 O 3 + __SO 2 What is the coefficient for O 2 when this equation is balanced using whole number coefficients? (A) 5 (B) 7 (C) 9 (D) 11 10. How many grams of MgCO 3 contain 24.0 g of oxygen? (The molar mass of MgCO 3 is 84.3 g mol¯ 1 ) (A) 42.2 g (B) 84.3 g (C) 126 g (D) 154 g 11. How many hydrogen atoms are present in one mole of ammonium benzoate, NH 4 C 7 H 5 O 2 ? (A) 6.0 x 10 23 (B) 2.4 x 10 24 (C) 3.0 x 10 24 (D) 5.4 x 10 24 12. Consider this balanced equation: 3 H 2 (g) + CO(g) ---> CH 4 (g) + H 2 O(g) How many moles of CH 4 can be obtained by reacting 2.0 mol of H 2 with 2.0 mol CO according to this equation? (A) 0.33 mol
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1999 - U.S. National Chemistry Olympiad: 1999 Local Section...

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