College Chemistry Ch 4

Calculations, Chemical Changes, and the Chemical Equation

Atomic Mass Unit (amu)

unit of measure for the mass of atoms

Avogadro’s number

1 mole of atoms =6.022×10²³atoms

basis for the concept of the mole

mole (mol)

a practical unit for defining a collection of atoms

counting unit

atomic mass

one atom of an element corresponds to average mass of a single atom in amu

molar mass

one mole of element corresponds to the mass of a mole of atoms in grams

chemical formula

a combination of symbols of the various elements that make up the compound

formula unit

the smallest collection of atoms that provide two important pieces of information including; the identity of the atoms or ions and the relative number of each type of atom or ion

hydrate

compounds containing one or more water molecules as an integral part of their structure

anhydrous

a substance containing no water molecules

formula mass

the sum of the atomic masses of all atoms in the compound as represented by its formula; expressed in amu

chemical equation

shorthand notation of a chemical reaction

reactants

(starting materials) the substances that undergo change in the reaction

products

substances produced by the reaction

calculating formula unit

when calculating the formula mass or molar mass of an ionic compound, the smallest unit of crystal is used

Delta

triangular symbol used to represent the energy needed for the transition from reactants to products

products and reactants must be ____ using ____ ____

specified, chemical, symbols

Evidence of a reaction occurring

• release of a gas

• formation of a solid (precipitate)

• Heat is produced or absorbed

• change in color

• change in electrical properties

Patterns of Chemical Reactions

Combination, Decomposition, Single Replacement, Double Replacement

Combination

the joining of two or more elements or compounds, producing a product of different composition

Decomposition

produce two or more products from a single reactant

Single Replacement

one atom replaces another in the compound producing a new compound

Double Replacement

two compounds undergo a “change of partners”

A chemical equation shows the ____ ____ of ____ needed to produce a particular ____ ____ of ____

A chemical equation shows the molar quantity of reactants needed to produce a particular molar quantity of products

law of conservation of mass

matter cannot be either gained or lost in the process of a chemical reaction

coefficient

how much of a specific substance is in the reaction

an ____ must be ____

equation, balanced