1998 nat - U.S. National Chemistry Olympiad: 1998 Local...

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U.S. National Chemistry Olympiad: 1998 Local Section Test Go to the answers 1. Which gas is most soluble in water? (A) ammonia (B) hydrogen (C) methane (D) nitrogen 2. For which family of elements does the melting point increase with increasing atomic mass? 1. alkali metals 2. halogens (A) 1 only (B) 2 only (C) both 1 and 2 (D) neither 1 nor 2 3. Which pair of substances could be separated by a simple distillation in a school laboratory? (A) ammonia and argon (B) salt and water (C) oil and vinegar (D) flour and sugar 4. Which compound is least soluble in water? (A) Al(NO 3 ) 3 (B) Na 3 PO 4 (C) K 2 SO 4 (D) PbCl 2 5. An object is dried by heating it in an oven. Which procedure would give the most accurate determination of its mass? (A) The object is weighed while it is still warm. (B) The object is weighed after being cooled on the laboratory bench. (C) The object is weighed after being cooled in a desiccator. (D) The object is weighed after being cooled by blowing air on it. 6. A sample of gas is to be identified by means of its behavior in the presence of a glowing
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splint. Which gas will neither itself burn nor cause the splint to burn? (A) oxygen (B) nitrogen (C) hydrogen (D) methane 7. A compound prepared as a model of hemoglobin is 4.6% iron by mass. If the compound is known to contain a single iron atom, which of these values will be closest to its molar mass? (A) 1000 g mol¯ 1 (B) 1200 g mol¯ 1 (C) 1400 g mol¯ 1 (D) 1600 g mol¯ 1 8. How many hydrogen atoms are present in 0.046g of ethanol, C 2 H 5 OH? (Molar Mass of C 2 H 5 OH is 46 g mol¯ 1 ) (A) 6.0 x 10 20 (B) 1.2 x 10 21 (C) 3.0 x 10 21 (D) 3.6 x 10 21 9. Which of these hydrated salts contains the greatest percentage of water by mass? (A) BaCl 2 · 2H 2 O (B) CuSO 4 · 5H 2 O (C) CaCl 2 · 6H 2 O (D) Ni(ClO 4 ) 2 · 6H 2 O 10. Ammonium dichromate, (NH 4 ) 2 Cr 2 O 7 , decomposes when heated to produce N 2 , H 2 O, and Cr 2 O 3 as represented by this equation. __(NH 4 ) 2 Cr 2 O 7 (s) ---> __N 2 (g) + __H 2 O(g) + __Cr 2 O 3 (s) What is the coefficient for H 2 O when this equation is correctly balanced using the smallest set of whole number coefficients? (A) 1 (B) 2 (C) 4 (D) 8 11. What volume of 0.15 M HCl can be made from 7.5 mL of concentrated HCl (12M)? (A) 0.060 L
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(B) 0.60 L (C) 6.0 L (D) 6.0 x 10 2 L 12. Hematite, Fe 2 O 3 , is the most common iron ore. How many moles of hematite are in an ore sample that contains 355 g of iron? Assume hematite is the only source of iron in this ore. (A) 1.11 mol (B) 1059 mol (C) 3.18 mol (D) 6.36 mol 13. How many moles of Mg(OH) 2 can be precipitated when 15 mL of 0.20 M MgCl 2 solution is mixed with 25 mL of 0.18 M KOH? (A) 0.0015 mol (B) 0.0022 mol (C) 0.0030 mol (D) 0.0045 mol 14. A 2.0 mL sample of HCl(g) is mixed with a 1.5 mL of NH 3 (g). What is the volume if the resulting mixture after the reaction is complete? (Assume all measurements are carried out at the same pressure and temperature and that the volume of the solid is negligible)
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1998 nat - U.S. National Chemistry Olympiad: 1998 Local...

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