MathDB

2008 National Chemistry Olympiad

Part of National Chemistry Olympiad

Subcontests

(8)
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2008 USNCO Local #17: Value of Properties

The value of which property decreases with an increase in the strength of intermolecular forces?
<spanclass=′latex−bold′>(A)</span>viscosity<spanclass=′latex−bold′>(B)</span>boiling point<spanclass=′latex−bold′>(C)</span>surface tension<spanclass=′latex−bold′>(D)</span>vapor pressure <span class='latex-bold'>(A)</span>\hspace{.05in}\text{viscosity}\qquad<span class='latex-bold'>(B)</span>\hspace{.05in}\text{boiling point}\qquad<span class='latex-bold'>(C)</span>\hspace{.05in}\text{surface tension}\qquad<span class='latex-bold'>(D)</span>\hspace{.05in}\text{vapor pressure}\qquad
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2008 USNCO Local #11: Moles of X, Y and Z

For the reaction: 2X+3Y→3Z2X + 3Y \rightarrow 3Z, the combination of 2.002.00 moles of XX with 2.002.00 moles of YY produces 1.751.75 moles of ZZ. What is the percent yield of this reaction? <spanclass=′latex−bold′>(A)</span>43.8%<spanclass=′latex−bold′>(B)</span>58.3%<spanclass=′latex−bold′>(C)</span>66.7%<spanclass=′latex−bold′>(D)</span>87.5%<span class='latex-bold'>(A)</span>\hspace{.05in}43.8\%\qquad<span class='latex-bold'>(B)</span>\hspace{.05in}58.3\%\qquad<span class='latex-bold'>(C)</span>\hspace{.05in}66.7\%\qquad<span class='latex-bold'>(D)</span>\hspace{.05in}87.5\%\qquad
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2008 USNCO Local #9: Moles of oxygen gas

How many moles of oxygen gas are produced by the decomposition of 245245 g of potassium chlorate?
\ce{2KClO3(s)} \rightarrow \ce{2KCl(s)} + \ce{3O2(g)}
Given: Molar Mass/ g⋅mol−1\text{g} \cdot \text{mol}^{-1} \ce{KClO3}: 122.6122.6
<spanclass=′latex−bold′>(A)</span>1.50<spanclass=′latex−bold′>(B)</span>2.00<spanclass=′latex−bold′>(C)</span>2.50<spanclass=′latex−bold′>(D)</span>3.00 <span class='latex-bold'>(A)</span>\hspace{.05in}1.50 \qquad<span class='latex-bold'>(B)</span>\hspace{.05in}2.00 \qquad<span class='latex-bold'>(C)</span>\hspace{.05in}2.50 \qquad<span class='latex-bold'>(D)</span>\hspace{.05in}3.00 \qquad
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2008 USNCO Local #3: Thickness of aluminum foil

A student wishes to determine the thickness of a rectangular piece of aluminum foil but cannot measure it directly. She can measure its density (d)(d), length (l)(l), mass (m)(m) and width (w)(w). Which relationship will give the thickness?
<spanclass=′latex−bold′>(A)</span>md⋅l⋅w<spanclass=′latex−bold′>(B)</span>m⋅l⋅wd<spanclass=′latex−bold′>(C)</span>d⋅l⋅wm<spanclass=′latex−bold′>(D)</span>d⋅ml⋅w<span class='latex-bold'>(A)</span>\hspace{.05in}\frac{m}{d \cdot l \cdot w} \qquad<span class='latex-bold'>(B)</span>\hspace{.05in}\frac{m \cdot l \cdot w}{d} \qquad<span class='latex-bold'>(C)</span>\hspace{.05in}\frac{d \cdot l \cdot w}{m} \qquad<span class='latex-bold'>(D)</span>\hspace{.05in}\frac{d \cdot m }{l \cdot w} \qquad
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2008 USNCO Local #1: Liquid element

Which element is a liquid at 25∘C25^\circ\text{C} and 1.0 atm1.0 \text{ atm}?
<spanclass=′latex−bold′>(A)</span>bromine<spanclass=′latex−bold′>(B)</span>krypton<spanclass=′latex−bold′>(C)</span>phosphorus<spanclass=′latex−bold′>(D)</span>xenon<span class='latex-bold'>(A)</span>\hspace{.05in}\text{bromine} \qquad<span class='latex-bold'>(B)</span>\hspace{.05in}\text{krypton} \qquad<span class='latex-bold'>(C)</span>\hspace{.05in}\text{phosphorus} \qquad<span class='latex-bold'>(D)</span>\hspace{.05in}\text{xenon} \qquad