Chemical Bonds, Accounting, and States of Matter

Covalent Bonds

nonmetallic, sharing of electrons; can share one, two, or three (single, double, triple bonds)

Binary Covalent

compounds named using prefix to denote the number of atoms (mono, di, tri, tetra, etc)

Electronegativity

measures an atom's attraction for the electrons in a bond

Polar Covalent Bonds

2 atoms with different electronegativities, electrons are pulled closer to the atom with a higher electronegativity

Bond polarity

represented by Lewis dot structure (higher electronegativity, more electrons on its element)

Electronegativity Difference

<0.5 Nonpolar covalent, 0.5-2.0 Polar Covalent, >2.0 Ionic

Polyatomic ions

covalently bonded atoms with a charge

Free Radicals

an atom/molecule with an unpaired electron (ex. NO, NO2, ClO2)

Molecular Shapes: VSEPR

Valence Shell Electron Pair Repulsion, predicts the shape of molecules and polyatomic ions based on repulsions of electron pairs on central atoms.

Chemical Equations

represent sentences and communicate chemical change

Reactants

present before reaction

Products

present after reaction

Coefficients

numbers used to balance the equation

Law of combining volumes

when all measurements are made at the same temperature and pressure, the volumes of a gaseous reactants and products are in small whole-number ratios

Avogadro's hypothesis

when measured at the same temp and pressure, equal volumes of all gases contain the same number of molecules

Avogadro's number

6.02 x 10^23

A mole (mol)

is the amount of substance that contains 6.02 x 10^23 particles

Formular mass/molecular mass

avg mass of a formula unit relative to that of a carbon-12 atom; sum of the atomic masses for all atoms in a formula

Molar volume of gas

one mole of any gas occupies a volume of 22.4 L at a standard temp and pressure (STP)

STP

is 1 atm of pressure and a temp of 0 C

Stoichiometry

quantitative relationship between reactants and products in a balanced chemical equation; the coefficients of the chem equ represent moles

Solution concentration

the amount of solute in a given solvent

Dilute solution

small amounts of solute in solvent

Concentrated solution

large amounts of solute in solvent

Molarity (M)

moles of solute per liter of solution

Percent Concentration

percent by volume = volume of solute/volume of solution x 100; percent by mass = mass of solute/mass of solution x 100

Melting Point

the temp at which a solid becomes a liquid

Vaporization

the process by which a liquid becomes a gas

Boiling Point

the temp at which the particles of a liquid escape and become a gas

Condensation

the process by which a gas becomes a liquid

Freezing

a liquid becomes a solid, occurs at freezing point

Sublimation

a solid changes directly from the solid to the gaseous state

Dipole forces

polar molecules are dipoles; oppositely charged ends attract each other

Hydrogen bonds

when a hydrogen atom is covalently bonded to a highly electronegative atom (like N, O, or F); can exhibit polar attraction

Dispersion forces/London dispersion forces

nonpolar molecules exhibit a dynamic induced dipole, the strength of which increases with molecular weight

Kinetic-Molecular Theory of Gas

1. The particles of a gas are in rapid, constant motion; 2. The particles of gas are tiny compared to the distances between them; 3. There is little attraction between the particles of a gas; 4. Collisions between gas molecules are perfectly elastic; 5. Temp is a measure of the average kinetic energy of gas molecules

Boyle's law

at a constant temp, the volume of a gas is inversely proportional to its pressure (V=1/P; V=a/P; PV=a)

Charles's law

at constant pressure, the volume of gas is directly proportional to its absolute temp (V=bT; V/T=b)

Avogadro's law

at fixed temp and pressure, the volume of gas is directly proportional to the amount of gas (V=cn; V/n=c)

Combined gas law

P1V1/T1 = P2V2/T2.

Acids

sour, litmus turns red, reactive with active metals to release hydrogen gas, react with bases to form water and a salt

Bases

bitter, litmus turns blue, slippery, reacts with acids to form water and salt

Arrhenius Theory

Acid—a molecular substance that ionizes in aq solution to form hydrogen ions (H+); Base—a substance that produces hydroxide ions (OH-) in aq solution

Bronsted-Lowry Theory

Acid—proton donor; Base—proton acceptor

Salts

ionic compounds composed of cations other than hydrogen and anions other than hydroxide

Neutralization

acid and base react together, water molecules and salt are the product; the amount of acid or base in a solution is determined by careful neutralization (titration)

pH

expresses acidity or basicity of a solution; means power of hydrogen

Conjugate acid-base pairs

compounds or ions that differ by one proton (ex. Cl- is the conjugate base of hydrochloric acid HCL)

Buffer solutions

contain a weak acid and its conjugate base; capable of maintaining nearly constant pH