chem exam 1

Chemistry

the study of the properties and behavior of matter

macroscopic

realm of ordinary-sized objects

Submicroscopic

realm of atoms and molecules

substance

matter with distinct properties and a composition that does not vary from sample to sample

Molecule

two or more atoms joined in a specific shape

diatomic molecules

H2, N2, O2, F2, I2, Cl2, Br2, Have No Fear Of Icee Cold Beer

elements in earth's crust

5 make up 90%

amount of named elements

118

elements in human body

3 make up 90%

mixtures

combination of two or more substances or components, the composition can vary unlike pure substances, exhibit the properties of the substances that make them

intensive property

independent of the amount of the substances present

extensive

depend upon the amount of the substance present

Energy

capacity to do work or transfer heat

isotopes

atoms of the same element with different masses and amounts of neutrons

subatomic particles mass

Pro and neu both have relative mass of 1, elec so small its ignored

atomic number

the number of protons in the nucleus of an atom, equals the \# of electrons

atomic weight

under the symbol of an element, the average mass found using all isotopes of an element weighted by their relative abundances; Isotope mass x fractional natural abundance+...

organization of periodic table

Elements in the same group have similar chemical properties; Rows- periods; Columns- groups

covalent/molecular compound

composed of molecules and almost always contain only nonmetals

Ions

an atom of a group of atoms that lost or gained an electron

Cation

formed when at least one electron is lost

Anion

Formed when at least one electron is gained

ionic compounds

generally formed between metals and nonmetals, electrons are transferred from the metal to the nonmetal, opposite charges attract, empirical formulas

polyatomic ion

A group of atoms that gains are loses electrons

Isomers

2+ molecules with the same chemical formula, but different structures

formula weight

the sum of atomic weights for the atoms in a chemical formula

solutions

homogeneous mixtures of two or more pure substances

solvent

present in greatest abundance

solutes

all other substances in a solution

aqueous solution

when water is the solvent

solvation

how all substances dissolve, surrounding of the solute by solvent

dissociation

Ionic compounds dissolve by water surrounding the separated ions

Molecular compounds dissolve in water

disperse in water, most remain intact, some form ions in water

electrolytes

a substance that dissociates into ions when dissolved in water

Ex: NaCl (s) forms Na⁺ (aq) and Cl^- (aq)

      CH₃CO₂H (aq) forms CH₃CO^- (aq) and H⁺ (aq)

strong electrolytes

dissociates completely when dissolved in water; equation has a single arrow, the solution is a strong conductor of electricity

HCl (aq)-> H⁺(aq)+ Cl^-(aq)

weak electrolytes

only dissociate partially when dissolved in water; equation indicates chemical equilibrium, a reaction goes both forward and backwards; double arrow

nonelectrolyte

may dissolve in water but does not dissociate into ions, the solution does not conduct electricity

Ex: C₆H₁₂O₆ (s) forms C₆H₁₂O₆ (aq)

       C₁₂H₂₂O₁₁ (s) forms C₁₂H₂₂O₁₁ (aq)

precipitation reaction

occur when two solutions containing soluble salts are mixed and an insoluble salt is produced; the solid is called a precipitate.

precipitate

the solid in a reaction

acids

substances that ionize in aqueous solutions to form H⁺, hydrogen ions; Strong acids completely dissociate in water, weak acids only partially

bases

substances that react with, or accept, H⁺ ions; increase concentration of OH^-, hydroxide ions, when dissolved in water; do not have to contain OH^- to be a base

strong bases

dissociate to metal cations and hydroxide anions in water

weak bases

only partially react to produce hydroxide anions

neutralization reaction

between an acid and a base;

ionic compound production

when the base is a metal hydroxide: water and salt

ionic compound written

if a weak electrolyte is involved it is not separated into ions

ionic compound carbonate or bicarbonate w/ acid reaction

the products are salt, carbon dioxide, and water

ionic compound sulfides

predicted results

oxidation and reduction

loss of electron; gain of electron

one cannot occur without the other, reactions are called redox reactions

concentration

the amount dissolved

molarity

one way to measure the concentration of the solution

titration

an analytical technique in which one can calculate the concentration of a solute in a solution

titrant

solution containing a known concentration of one reactant

analyte

solution containing reactants of unknown amount of concentration

standard solution

solution of known concentration; used to determine the unknown concentration of another solution

equivalence point

when the reaction is complete; based on the seen end point

indicators

added to cause a change in color near the equivalence point of titration

end point

the volume of titrant actually measured

thermodynamics

study of energy and its transformations

thermochemistry

study of chemical reactions and energy changes involving heat

Electrostatic potential energy

most important form of potential energy in changed particles

attraction between ions

opposites attract; bonds are formed- energy is released (E_el<0) bonds are broken- energy is consumed (E_el>0)

system

the portion of the universe we single out to study (represented by a chemical reaction)

open, closed, and isolated systems

can exchange heat and mass with its surroundings; only heat can be exchanged; heat and mass cannot be exchanged

positive and negative ΔE

system gains energy from the surroundings; system loses energy to the surroundings

internal energy of a system

the sum of all kinetic and potential energies of all components of the system; Generally don’t know it just how it changes

state functions

depends on present state of system not path to get to that state; ex- internal energy

enthalpy

represented as H; extensive; reverse reaction= opposite sign; the change depends on the states of reactants and products

calorimetry

the measurement of heat flow; we dk the enthalpy of the reactants and products so we use this to measure ΔH

heat capacity

the amount of energy(E) required to raise the temperature(T) of a substance by 1K (1*C)

specific heat

E needed to heat 1 gram of a substance by 1*C

molar heat capacity

E needed to heat 1 mole of a substance by 1*C

The enthalpy is associated with

breaking one mole of a particular bond in gaseous substance

bond enthalpy is always positive bc

Energy is required to break chemical bonds

The greater the bond enthalpy

the stronger the bond

Electromagnetic radiation

moves as waves through space at the speed of light

Wavelength λ

distance between corresponding points on adjacent waves

frequency

the number of waves passing a given point per unit of time 

Three observed properties associated with how atoms interact with electromagnetic radiation that cannot be explained by waves

Blackbody radiation- the emission of light from hot objects, Photoelectric effect- emission of electrons from metal surfaces on which light is shown, and Emission spectra- emission of light from electronically excited gas atoms

quanta

packets that energy comes in

As an electron changes energy states

energy is emitted or absorbed by the electron as a photon 

n_f>n_{i vs} n_f<n

a photon is absorbed, emitted

Quantum mechanics

mathematical treatment in which both the wave and particle nature of matter could be incorporated

uncertainty principle

the more precisely you know the momentum the less you know the position

n

principal quantum number; describes energy level; as it increases the orbital and electrons energy increase

l

Defines the shape(type) of orbital; range 0 to n-1

m

describes 3D orientation of the orbital; range -l to l; spinning up +½ down -½

orbital

a region of probability where an electron can be found

s orbital

L is 0; Sphere shape; # of peaks = n; L or # of nodes (zero probability of finding an electron) = n-1

p orbital

L =1 ; infinity sign shaped

d orbital

L = 2; An x or infinity + donuts

f orbital

L=3; Complicated shapes

Pauli exclusion principle

No two electrons in the same atom can have the same set of four quantum numbers, No two electrons in the same atom can have the exact same energy

electron configuration

the way electrons are distributed in an atom 

ground state

most stable organization and lowest possible energy

Hund’s rule

For a set of orbitals in the same sublevel there must be one electron in each orbital before pairing and the electrons have the same spin 

Valence electrons

Elements in the same group of the periodic table with the same number of electrons in the outermost shell 

core electrons (noble gases)

filled inner shell electrons

types of chemical bonds

Ionic (electrostatic attraction between ions), Covalent (sharing of electrons), Metallic (free electrons hold metal atoms together)

ionic bonding

between metals and nonmetals, very exothermic, 1 element readily gives up an electron (low ionization energy), Another element readily gains an electron (high electron affinity)