Chapter 3.1-3.5 Review packet Balancing and Stoichiometry

# Knowing that sodium reacts with water to form sodium

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17. Knowing that sodium reacts with water to form sodium hydroxide and hydrogen gas, you may reasonably predict that ____________. a. sodium will react with hydrogen gas to form sodium hydride b. potassium will react with water to form potassium hydroxide and hydrogen gas c. potassium will react with sodium d. sodium will react with water to form sodium hydride e. sodium hydroxide will react with water to form sodium oxide 18. Which pair of elements would you expect to exhibit the greatest similarity in their physical and chemical properties? 19. Which pair of elements would you expect to exhibit the greatest difference in their physical and chemical properties? 20. Currently, the atomic mass unit is based on what element?

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21. The atomic masses in the periodic table are not integral numbers. For example, carbon is listed as 12.01115 instead of 12.00000. Why? a. Our technology does not allow for exact measurement of such a small quantity. b. Atoms gain and lose electrons easily and that changes their masses significantly. c. Atomic masses listed in the periodic table are weighted averages of isotopic masses. d. Atomic masses are measured in real samples that are always contaminated with other elements. e. There is a theoretical uncertainty in the masses of atoms. 22. Given the information below, calculate the weighted average atomic mass (amu) of the element X. Isotope Abundance (%) Mass(amu) 221 X 74.22 220.9 220 X 12.78 220.0 218 X 13.00 218.1
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