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1 | |
The conversion of water to ice is considered a physical change, whereas the conversion of iron to rust is considered a chemical change. Why? |
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2 | |
How can you show that water is a compound rather than a homogeneous mixture of hydrogen and oxygen? |
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3 | |
Heating is a physical process. When mercuric oxide is heated, it becomes mercury and oxygen. Does this mean that mercuric oxide is a mixture rather than a compound? |
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4 | |
Which of the following substances are homogeneous and which are heterogeneous? Blood, carbon dioxide gas, solid carbon dioxide, rock, steak, iron, rust, concrete, air, oxygen, salt, milk. |
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5 | |
Which of the following homogeneous liquids are elements, which are compounds, and which are solutions? Alcohol, mercury, liquid hydrogen, pure water, seawater, beer. |
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6 | |
How does the law of definite proportions help to distinguish between a compound of certain elements and a mixture of the same elements? |
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7 | |
What is the most abundant element in the universe? In the human body? |
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8 | |
From what physical and chemical characteristics of iron do we conclude that it is a metal? From what physical and chemical characteristics of sulfur do we conclude that it is a nonmetal? |
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9 | |
Sodium never occurs in nature as the free element, and platinum seldom occurs in combination. How are these observations related to the chemical activities of the two metals? |
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10 | |
Are the chemical properties of the elements in a vertical column or in a horizontal row of the periodic table similar to one another? |
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11 | |
The element astatine (At), which appears at the bottom of the halogen column in the periodic table, has been prepared artificially in minute amounts but has not been found in nature. Using the periodic law and your knowledge of the halogens, predict the properties of this element, as follows:
a. At room temperature, is it solid, liquid, or gaseous?
b. How many atoms does a molecule of its vapor contain?
c. Is it very soluble, moderately soluble, or slightly soluble in water?
d. What is the formula for its compound with hydrogen?
e. What are the formulas for its compounds with potassium and calcium?
f. Is its compound with potassium more or less stable than potassium iodide? |
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12 | |
The following metals are listed in order of decreasing chemical activity: potassium, sodium, calcium, magnesium. How does this order agree with their positions in the periodic table? Where would you place cesium in the above list? |
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13 | |
(a) What is characteristic about the outer electron shells of the alkali metals? (b) Of the halogens? (c) Of the inert gases? |
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14 | |
Group 2 of the periodic table contains the family of elements called the alkaline earths. How active chemically would you expect an alkaline earth element to be compared with the alkali metal next to it? Why? |
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15 | |
Why do fluorine and chlorine exhibit similar chemical behavior? |
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16 | |
Why do lithium and sodium exhibit similar chemical behavior? |
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17 | |
Electrons are much more readily liberated from metals than from nonmetals when irradiated with visible or ultraviolet light. Can you explain why this is true? From metals of what group would you expect electrons to be liberated most easily? |
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18 | |
The rare element selenium has the following arrangement of electrons: 2 in the first shell, 8 in the second, 18 in the third, and 6 in the fourth. Would you expect selenium to be a metal or a nonmetal? |
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19 | |
A century ago an entirely new group of elements, the inert gases, was discovered. Is it possible that, in the future, another as yet unknown group of the periodic table might be found? |
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20 | |
Would you expect magnesium or calcium to be the more active metal? Explain your answer in terms of atomic structure. |
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21 | |
What is the difference in atomic structure between the two isotopes of chlorine? How would you account for the great chemical similarity of the two isotopes? |
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22 | |
(a) Would you expect N or Br to differ most in its chemical properties from F? (b) B or Si from C? (c) P or O from N? |
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23 | |
Why are chlorine atoms more chemically active than chlorine ions? |
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24 | |
The Bronze Age got its name from the ability of people in that stage of human development to refine tin and copper from their ores; bronze is an alloy (mixture) of tin and copper and is stronger than either of these metals by itself. In the later Iron Age, the still stronger iron could be won from its ores. Nowadays metals such as aluminum and magnesium are refined electrically. Relate this sequence of metallurgical skill to the sequence of metal activity in Table 9-2 (tin belongs between lead and iron in the table). |
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25 | |
More energy is needed to remove an electron from a hydrogen molecule than from a hydrogen atom. Why do you think this is so? |
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26 | |
Illustrate with electronic diagrams (a) the reaction between a lithium atom and a fluorine atom, and (b) the reaction between a magnesium atom and a sulfur atom. Would you expect lithium fluoride and magnesium sulfide to be ionic or covalent compounds? |
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27 | |
Why do the inert gas atoms almost never participate in covalent bonds? |
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28 | |
What is the difference in meaning between C4 and 4C? |
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29 | |
What energy change would you expect when a molecule breaks up into its constituent atoms? |
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30 | |
Which of the following compounds do you expect to be ionic and which covalent? IBr, NO2, SiF4, Na2S, CCl4, RbCl, Ca3N2. |
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31 | |
What is the charge on alkali metal ions? On halogen ions? On oxygen ions? |
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32 | |
The transition elements in any period have the same or nearly the same outer electron shells and add electrons successively to inner shells. How does this bear upon their chemical similarity? |
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33 | |
The formula for liquid water is H2O, for solid zinc sulfide ZnS, and for gaseous nitrogen dioxide NO2. Precisely what information do these formulas convey? What information do they not convey? |
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34 | |
How many atoms of which elements are present in a molecule of (C2H5)3N? |
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35 | |
How many atoms are present in a molecule of C3H5(OH)3? How many of them are hydrogen atoms? |
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36 | |
Name these compounds: CaMnO4, CaWO4, Ca3(AsO4)2. |
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37 | |
Name these compounds: BaH2, Li3PO4, PbO, CuBr2, KOH. |
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38 | |
Write the formulas of these compounds: sulfur trioxide; phosphorus pentachloride; dinitrogen tetroxide. |
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