Ch. 4: Compounds and Stoichiometry

Question 1

Compounds

Answer 1

Substances composed of 2 or more elements in a fixed proportion

Question 2

Molecular Weight

Answer 2

Mass in (amu) of the constituent atoms in a compound as indicated by the molecular formula

Question 3

Molar mass

Answer 3

Mass of one mole (Avogadro’s number) of a compound; usually measured in grams per mole

Question 4

Gram equivalent weight

Answer 4

Measure of the mass of asubstance that can donate one equivalent of the species of interest

Question 5

Normality

Answer 5

Ratio of equivalents per liter; it is related to molarity by multiplying the molarity by the number of equivalents present per mole of compound

Question 6

Equivalents

Answer 6

Moles of the species of interest; equivalents are most often seen in acid-base chemistry (hydrogen ions or hydroxide ions) and oxidation-reudction reactions (moles of electrons or other ions)

Question 7

Law of constant composition

Answer 7

States that any pure sample of a compound will contain the same elements in the same mass ratio

Question 8

Empirical Formula

Answer 8

Smallest whole-number ratio of the elements in a compound

Question 9

Molecular Formula

Answer 9

Either the same as or a multiple of the empirical formula; it gives the exact number of atoms of each element in a compound

Question 10

Percent Composition by Mass

Answer 10

Determine the mass of the individual element and divide by the molar mass of the compound

Question 11

Combination Reaction

Answer 11

Occur when 2 or more reactants combine to form one product

Question 12

Decomposition Reaction

Answer 12

Occur when one reactant is chemically broken down into 2 or more products

Question 13

Combustion reaction

Answer 13

Occurs when a fuel and an oxidant (typically oxygen) react, forming the products water and carbon dioxide (if the fuel is a hydrocarbon)

Question 14

Displacement Reactions

Answer 14

Occur when one or more atoms or ions of one compound are replaced w one or more atoms or ions of another compound

Question 15

Single Displacement Reactions

Answer 15

Occur when an ion of one compound is replaced with another element

Question 16

Double Displacement Reactions

Answer 16

Occur when elements from 2 diff compounds trade places w each other to form 2 new compounds

Question 17

Neutralization Reactions

Answer 17

Are those in which an acid reacts with a base to form a salt (and, usually, water)

Question 18

Balancing a Chemical Equation

Answer 18

Chemical equations must be balanced to perform stoichiometric calculations

1. Balance the least common atoms
2. Balance the more common atoms (usually hydrogen and oxygen)
3. Balance the charge, if necessary

Question 19

Limiting Reagent

Answer 19

The reactant that will be consumed first in a chemical rxn

Question 20

Excess Reagent

Answer 20

Reactants that are not limiting

Question 21

Theoretical Yield

Answer 21

Amt of product generated if all of the limiting reactant is consumed w no side reactions

Question 22

Actual Yield

Answer 22

Typically lower than theoretical yield

Question 23

Percent yield

Answer 23

Calculated by dividing actual yield by theoretical yield and converting to a percentage

Question 24

Roman Numerals

Answer 24

Used for nonrepresentative elements to denote ionic charge

Question 25

-ous

Answer 25

Can be used to indicate lesser charge (cations)

Question 26

-ic

Answer 26

Can be used to indicate greater charge (cations)

Question 27

-ide

Answer 27

All monoatomic anions end in -ide

Question 28

Oxyanion suffix to indicate oxidation

Answer 28

Indicate how oxidized the central atom is

• Less oxygen are given suffix -ite
• More oxygen are give -ate

Question 29

Oxyanion series w more than 2 members

Answer 29

Fewest oxygens given prefix hypo-, the most oxygens is given prefix per-

Question 30

Polyatomic ions containing hydrogen

Answer 30

polyatomic ions containing hydrogen denote the number of hydrogens using hydrogen or bi to denote one, or dihydrogen to denote 2

Question 31

Ionic Charges

Answer 31

Predictable by group number and type of element (metal or nonmetal) for representative elements, but are generally unpredictable for nonrepresentative elements

• Metals form positively charged cations based on group number
• Nonmetals form negatively charged anions based on the number of electrons needed to achieve an octet

Question 32

Electrolytes

Answer 32

Contain equivalents of ions from molecules that dissociate in solution. The strength of an electrolyte depends on its degree of dissociation or solvation