Chem 101 Exam 3 Study Guide UPDATED ACTUAL Questions And Correct Answers
C
Terms in this set (132)
Compounds When elements combine with each other, they form compounds
- The great diversity of substances found in nature is a direct result of the ability of
elements to form compounds.
Hydrogen (Selected Properties) Boiling Point: -253 C
State at room temperature: Gas
Flammability: Explosive
Oxygen (Selected Properties) Boiling Point: -183 C
State at room temperature: Gas
Flammability: Necessary for combustion
Water (Selected Properties) Boiling Point: 100 C
State at room temperature: Liquid
Flammability: Used to extinguish flame
Definite Proportion A hydrogen-oxygen mixture can have any proportions of hydrogen and oxygen
gas.
Water, by contrast, is composed of water molecules that always contain two
hydrogen atoms to every one oxygen atom.
- Water has a definite proportion of hydrogen to oxygen
Chemical bonds Results from the attractions between the charged particles (electrons and
protons) that compose atoms
Compounds are composed of atoms held together by chemical bonds
- Ionic bonds
- Covalent bonds
Ionic bonds (Chemical bonds) Occur between metals and nonmetals
- Involve transfer of electrons from the metal atom to the nonmetal atom
- These oppositely charged ions attract one another by electrostatic forces and
form an ionic bond
Formula unit Basic unit of an Ionic compound
- Smallest, electrically neutral collection of ions
, Lattice A regular three-dimensional array of alternating cations and anions.
- In a solid phase, the ionic compounds is composed of a lattice
Covalent Bonds (Chemical bonds) Occurs between two or more nonmetals
- Two atoms share electrons between them which compose a molecule
AKA Molecular compounds
Chemical formula elements present in the compound and the relative number of atoms or ions of
each
Indicates the relative quantities of each element in a compound
Ex.
H2O
NaCl
CO2
CCl4
Empirical formula (Chemical formula) Gives the relative number of atoms of each element in a compound
Simplest Whole-number ratio of the atoms or moles of elements in a compound
- NOT a ratio of masses
Communicates the least information
Finding an Empirical Formula 1. Convert the percentages to grams.
- Assume you start with 100 g of the compound
- Skip if it is already in grams
2. Convert grams to moles
3. Write a pseudoformula using moles as subscripts
4. Divide all by the smallest number of moles
5. Multiply all mole ratios by a number to make all whole numbers
Molecular formula (Chemical Formula) Gives the actual number of atoms of each element in the molecule of a
compound
Structural formula (Chemical formula) Uses lines to represent covalent bonds and shows how atoms in a molecule are
connected or bonded to each other
- Also shows the molecule's geometry
Communicates the most information
Molecular model More accurate and complete way to specify a compound
Ball-and-stick molecular model (Molecular model) Represents atoms as balls and chemical bonds as sticks; how the two connect
reflects a molecule's shape.
C
Terms in this set (132)
Compounds When elements combine with each other, they form compounds
- The great diversity of substances found in nature is a direct result of the ability of
elements to form compounds.
Hydrogen (Selected Properties) Boiling Point: -253 C
State at room temperature: Gas
Flammability: Explosive
Oxygen (Selected Properties) Boiling Point: -183 C
State at room temperature: Gas
Flammability: Necessary for combustion
Water (Selected Properties) Boiling Point: 100 C
State at room temperature: Liquid
Flammability: Used to extinguish flame
Definite Proportion A hydrogen-oxygen mixture can have any proportions of hydrogen and oxygen
gas.
Water, by contrast, is composed of water molecules that always contain two
hydrogen atoms to every one oxygen atom.
- Water has a definite proportion of hydrogen to oxygen
Chemical bonds Results from the attractions between the charged particles (electrons and
protons) that compose atoms
Compounds are composed of atoms held together by chemical bonds
- Ionic bonds
- Covalent bonds
Ionic bonds (Chemical bonds) Occur between metals and nonmetals
- Involve transfer of electrons from the metal atom to the nonmetal atom
- These oppositely charged ions attract one another by electrostatic forces and
form an ionic bond
Formula unit Basic unit of an Ionic compound
- Smallest, electrically neutral collection of ions
, Lattice A regular three-dimensional array of alternating cations and anions.
- In a solid phase, the ionic compounds is composed of a lattice
Covalent Bonds (Chemical bonds) Occurs between two or more nonmetals
- Two atoms share electrons between them which compose a molecule
AKA Molecular compounds
Chemical formula elements present in the compound and the relative number of atoms or ions of
each
Indicates the relative quantities of each element in a compound
Ex.
H2O
NaCl
CO2
CCl4
Empirical formula (Chemical formula) Gives the relative number of atoms of each element in a compound
Simplest Whole-number ratio of the atoms or moles of elements in a compound
- NOT a ratio of masses
Communicates the least information
Finding an Empirical Formula 1. Convert the percentages to grams.
- Assume you start with 100 g of the compound
- Skip if it is already in grams
2. Convert grams to moles
3. Write a pseudoformula using moles as subscripts
4. Divide all by the smallest number of moles
5. Multiply all mole ratios by a number to make all whole numbers
Molecular formula (Chemical Formula) Gives the actual number of atoms of each element in the molecule of a
compound
Structural formula (Chemical formula) Uses lines to represent covalent bonds and shows how atoms in a molecule are
connected or bonded to each other
- Also shows the molecule's geometry
Communicates the most information
Molecular model More accurate and complete way to specify a compound
Ball-and-stick molecular model (Molecular model) Represents atoms as balls and chemical bonds as sticks; how the two connect
reflects a molecule's shape.
