Chem 161-2010 Chapter 2 some Tavss practice problems + solutions

Chem 161-2010 Chapter 2 some Tavss practice problems + solutions

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Unformatted text preview: CHAPTER 2 - ATOMS, MOLECULES AND IONS 1 FUNDAMENTAL CHEMICAL LAWS 21 Chapter 2 Atoms, molecules and ions Fundamental chemical laws When 10.00 g of arsenic reacts with excess oxygen, a compound of arsenic and oxygen with a mass of 15.35 g is formed. What mass of oxygen reacted? As + O 2 As m O n 10.00g ?g 15.35g According to the law of conservation of mass, the 10.00g of As reactant must go into the product, assuming that the reaction went to completion. Since the product only contains As and O, then the balance of the 15.35g, i.e., 5.35g, must be oxygen. A. 0.200 g B. 5.35 g C. 32.0 g D. 96.0 g E. Not enough information is given to answer this question. B 18 Chapter 2 Fundamental chemical laws The Law of Multiple Proportions works because A. Atoms only contain whole numbers of protons and neutrons. B . Atoms combine only in whole number ratios. C. Compounds form either from ions or combine as molecules. D. Atomic masses reduce to simple whole number ratios. E. Ions are formed by losing or gaining whole numbers of electrons. A. True, but irrelevant. B. This is the essence of the Law of Multiple Proportions. C. True, but irrelevant. D. Gibberish; this has no meaning. E. True, but irrelevant. 2 6. Chapter 2 Fundamental Chemical Laws Rutherfords experiment was important because it showed that: A. radioactive elements give off alpha particles B. gold foil can be made only a few atoms thick C. the neutron is slightly heavier than the proton D. the mass of an atom is uniformly distributed throughout the atom E . an atom is mostly empty space If the particles within an atom were distributed evenly (the plum pudding model), then the alpha particles that Rutherford used to bombard the aluminum foil would have met virtually no resistance, and would have gone fairly straight through the aluminum foil. However, since the vast majority of alpha particles passed straight through the aluminum foil, but a very small number of alpha particles didnt pass through the aluminum foil then this indicated that the atoms in the aluminum foil consisted of some very dense small units within a lot of empty space. 16. Chapter 2 Fundamental Chemical Laws The charge to mass ratio of an electron is 1.76 x 10 8 C/g and the charge of an electron is 1.602 x 10-19 C. The mass of the electron is A . 9.10 x 10-28 g B. 9.11 x 10-31 g C. 1.11 x 10-27 g D. 1.11 x 10 27 g E. 1.11 x 10-28 g Use a simple proportion:-1.76 x 10 8 C/g = -1.602 x 10-19 C/Xg 3 X = 9.10 x 10-28 g 18 Chapter 2 Fundamental chemical laws The Law of Multiple Proportions works because A. Atoms only contain whole numbers of protons and neutrons. B . Atoms combine only in whole number ratios. C. Compounds form either from ions or combine as molecules....
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Chem 161-2010 Chapter 2 some Tavss practice problems + solutions

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