General Chemistry: Atoms in Reaction

Quantitative Measures of elements and compounds

1.660539 × 10 ^-24 g

1 atomic mass unit (amu) is equal to___.

relative atomic mass

dividing the mass of an atom with the atomic mass unit

average atomic mass

value indicated in the periodic table, weighted average of the atomic masses of the known stable isotopes of an element based on percent isotopic abundances.

Avogadro’s number (N _{A )}

constant used to quantify the number of particles of an element (atoms, ions) or compound (molecules, formula units)

molecule

particle unit of covalent compounds

formula unit

particle unit of ionic compound

6.022 × 10 ²³

Amedeo Avogadro’s value; value of 1 mole

mole (mol)

term used to refer to the quantity of particles of a substance (atoms, ions, molecules, or formula units) that is equal to the Avogadro’s number

International Union of Pure and applied chemistry (IUPAC)

defined mole as the amount of substance of a system, which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12

equal

the number of moles of an atom is ___ to the atom’s subscript in the chemical formula.

concept of mole

relates the atomic scale to the macroscale of matter; from atoms to moles to grams to liters

amu

used in atomic scale

gram

used in molar scale

molar mass (MM)

mass of one mole of an element or compound, which is numerically equal to the atomic mass of the element, the molecular mass of a covalent compound, formula mass of a ionic compound

molar mass

obtained as the sum of the product of atomic masses and the number of atoms of every element comprises the compound

stoichiometric coefficients

numbers before the chemical formula or element symbol, which indicate the mole ratio among the reactants and products of a reaction

(aq) symbol

means aqueous solution - substance is dissolved in water

• change in color

• evolution of gas (formation of bubbles)

• evolution or absorption of heat (warming, cooling, formation of sparks or flame)

• formation of a precipitate (an insoluble solid)

• change in odor

a chemical reaction is always accompanied by a chemical change evidenced as any of the following

1. Synthesis (or Combination) Reactions

2. Decomposition (or Analysis) Reactions

3. Single Replacement (or Substitution) Reactions

4. Double Replacement (or Metathesis) Reactions

Basic types of chemical reactions

synthesis (combination)

two or more reactants combine to form a single product; can be a combination of nonmetal and metal, two nonmetals, or even be an addition of two compounds

decomposition (analysis)

reverse of synthesis reactions; involves only one reactant dissociating into two or more products

single replacement (substitution)

one element of a compound is replaced by a different element

single replacement reaction

a more active free metal can replace a less active one in a compound

free metal

from the activity series (increasing electronegativity), ____ can replace the ions of those below it from its compound

H_²

the only nonmetal listed in the activity series (increasing reactivity)

F > Cl > Br > I

reactivity series for halogens (nonmetal X replace nonmetal in a compound

double replacement (metathesis)

occurs when two ionic compounds exchange cations and anions with each other.

1. Neutralization

2. Precipitation

3. Reduction-oxidation or redox

Reactions involving aqueous solutions

neutralization reaction

involves an acid and base; follows a double replacement type where the products are salt and water

cation of the salt comes from the base; anion from the acid

precipitation

also a double replacement type, where an insoluble solid called precipitate is formed; involves two ionic compounds as reactants and forms a water-soluble salt as the other product.

solubility rule

the formation of AgCl or other precipitates can be predicted using this for ionic compounds

oxidation

process in which an atom loses an electron, resulting in an increase in the oxidation number of that atom.

reduction

process where an atom gains an electron, resulting in a decrease in its oxidation number.

oxidation number of an atom

indicates the number of electrons that have been removed or added to get to its new state.

transfer of electrons and changes in oxidation numbers

oxidation and reduction always come together, and always involve ____.

reducing agent

substance that is oxidized because it causes the reduction of the other substance.

oxidizing agent

substance that is reduced because it causes the oxidation of the reducing agent.

actual yield

is less than the theoretical yield, oftentimes

percent yield

the ratio between the actual yield and the theoretical yield

limiting agent

this substance is consumed completely in the reaction. once this is used up, the reaction no longer proceeds and so does the formation of products

excess reagent

the other reactant which will have some unreacted amount after the reaction.