Download representing chemical compounds

Name ________________________________________ Class _________________ Date _______________
REPRESENTING CHEMICAL COMPOUNDS
6.2
SECTION REVIEW
Objectives
• Distinguish among chemical formulas, molecular formulas, and formula units
• Use experimental data to show that a compound obeys the law of definite
proportions
Key Terms
• chemical formula
• molecular formula
• formula unit
• law of definite proportions
• law of multiple proportions
Part A Completion
Use this completion exercise to check your understanding of the concepts and terms
that are introduced in this section. Each blank can be completed with a term, short
phrase, or number.
Chemists have identified more than ten million chemical
1
.A
2
shows the kinds and numbers of atoms in
the smallest representative unit of a substance.
The chemical formula of a molecular compound is called a
3
. If there is more than one atom of a given element in a
molecule, a
4
is used to indicate the number of atoms.
For an ionic compound, the smallest whole-number ratio
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of atoms in the compound is called a
The law of
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5
1.
2.
3.
4.
5.
6.
7.
.
proportions states that the masses of
elements in a compound are always in the same proportions.
This is consistent with Dalton’s theory that atoms combine in
7
ratios.
Review Module / Chapters 5–8
33
Name ________________________________________ Class _________________ Date _______________
Part B True-False
Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.
________ 8. The molecular formula for table salt is NaCl.
________ 9. Whenever two elements form more than one compound, the different
masses of one element that combine with the same mass of the other
element are in the ratio of small whole numbers.
________ 10. The proportions of elements in a sample of a compound vary with the
mass of the sample.
________ 11. A subscript in a chemical formula is used to indicate the number of
atoms of a given element in the smallest representative unit of the
substance.
________ 12. A chemical formula is the same as a molecular formula.
Part C Matching
Match each description in Column B to the correct term in Column A.
Column B
________ 13. chemical formula
a. chemical formula for a molecular compound
________ 14. molecular formula
b. chemical formula for an ionic compound
________ 15. formula unit
c. in any sample of a compound, the masses of the
elements are always in the same proportions
________ 16. subscript
d. shows the kinds and numbers of atoms in the smallest
representative unit of a substance
________ 17. law of definite
proportions
e. used to indicate the number of atoms of an element
present in a molecule
Part D Questions and Problems
Answer the following question in the space provided.
18. Classify each of the following chemical formulas as a molecular formula or a
formula unit.
a. NaBr
b. CaCl2
c. C2H6
d. K2S
e. CCl4
f. H2O
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Review Module / Chapters 5–8
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Column A