WS2_key - Chem 142 Name Worksheet 2 Atoms Molecules and...

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Chem 142 Summer 2011 Page 1 of 3 Name ________________________________________ Section ________________ Worksheet 2: Atoms, Molecules and Ions 1. A 5.00g sample of magnesium phosphate contains 1.39g of magnesium. How much magnesium would a 1.00 kg sample contain? mass fraction = 1.39 g Mg 5.00 g sample = 0.278 Mg sample ( ) mass magnesium = 0.278 Mg sample ( ) ! 1.00 kg = 0.278 kg 2. What mass of sodium is in a 4.6g sample of sodium nitrate? M NaNO 3 = 22.990 + 14.001 + 3 ! 15.999 ( ) = 84.995 g mol mass fraction = 22.990 g Na 84.995 g sample = 0.271 Na sample ( ) mass sodium = 0.271 Na sample ( ) ! 4.6 g sample = 1.2 g Na 3. For each of the following statements, classify the statement as true or false and explain. a. Protons, neutrons and electrons all have approximately the same mass. False, electrons are 3 orders of magnitude smaller than protons and neutrons. b. Atoms with the same number of protons have identical chemical properties. True, the type of element is determined by the number of protons, any atom of the same element will have identical chemical properties. c. All neutral atoms of an element have the same number of protons, neutrons and electrons.
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