Hmwk1 - finds that the mass ratio of lead to cadmium is...

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Chem 2070 Fall 2011 Homework #1 Due September 2 1. Tungsten (W) and chlorine (Cl) form a series of compounds with empirical formulas WCl x . If a series of such compounds are found to be 72.17%, 56.45%, 50.91% and 46.36% W by mass (and the rest of the mass is, of course, chlorine), find the four values of x. (Average mass of W is 183.84; average mass of Cl is 35.453.) 2. Only two isotopes of B occur naturally; the lighter 10 B (abundance 19.61, mass 10.013) and heavier 11 B (abundance 80.39, mass to be determined). Given that the periodic table lists the average mass of boron as 10.811, what is the mass of a 11 B atom? 3. A compound is analyzed and determined to be 94.85% Br by mass, 0.40% H by mass, and 4.75% C by mass. Determine its empirical formula. 4. A low melting alloy of tin (Sn), cadmium (Cd) and lead (Pb) is analyzed by two different methods; the first finds that the mole ratio of tin to lead is 2.73:1.00; while the second
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Unformatted text preview: finds that the mass ratio of lead to cadmium is 1.78:1.00. Find the mass percent composition of this alloy. 5. Page 62 of the text lists the masses of the electron, neutron and proton. Using those masses, find the % mass of an F atom (only one isotope exists!) associated with (a) the protons, (b) the neutrons, (c) the nucleus, and (d) the electrons. Compare the total mass you calculate to the measured mass found in the periodic table. 6. Fill in the gaps found in the table below: (you should probably reproduce the table on your homework page!) Unless indicated otherwise, you may assume (1) a neutral species, and (2) that we are looking for “abundant” species, not isotopes of low abundance/short lifetimes. Name Symbol # protons # neutrons # electrons mass Sodium 2 1 3 1 Na 11 12 11 23 Silicon 37 85 40 K 1+ 126 42 33...
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This document was uploaded on 10/26/2011 for the course CHEM 207 at Cornell.

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