CHEM 115

Limiting Reactant

Reactant completely consumed in reaction, limits how much reaction can take place

Theoretical Yield

Calculated greatest amount of product that could be produced by a reaction based on amount of limited reactant

Actual Yield

The amount of product that is actually made

Percent Yield

Actual/Theoretical Yield x 100%

Solvent

Substance of greatest quantity, often a liquid

Solute

Substance dissolved in Solvent

Electrolyte

Solute that produces ions when dissolved in a solvent, capable of conducting electricity.

Nonelectrolyte

Solute that does not ionize in water, when dissolved forms nonconducting solution

Solvation

Clustering of solvent molecules around solute particles

Strong electrolytes

Solutes in solution (near) completely as ions

ex. water soluble compounds

Weak electrolytes

solutes that exist as neutral molecules in solution, only partially form ions

Chemical Equilibrium

relative numbers of each type of ion/molecule are constant in a reaction

precipitation reaction

Reactions that result in insoluble product

Precipitate

insoluble solid formed by reaction in solution

Solubility

the ability of a substance to dissolve in a solvent.

Insoluble

substance w/ solubility <0.01 mol/L

Exchange (Metathesis) Reactions

reactions that involve the swapping of cations/anions b/n 2 reactants, forming 2 new compounds

AX+BY → AY+BX

AgNO3+KCl → AgCl+KNO3

Molecular Equation

Chemical equation where formula for each substance is written (reactants & products)

Complete ionic equation

equation written w/ all soluble strong electrons shown as ions

Spectator ions

ions that appear in identical forms on both sides of complete ionic equations, play no direct role in reaction can be cancelled out in reaction

Acids

Proton donors, Substances that ionize in aqueous solutions to form hydrogen ions (essentially just a proton)

Monoprotic vs. diprotic acid acid

Monoprotic - one H+ per molecule of acid

Diprotic - two H+ per molecule of acid

Bases

substances that accept H+ ions, produce hydroxide ions (OH-) when dissolved in water

Strong/Weak acids/bases

acids/bases completely ionized or partially ionized based on strong/weak electrolytes

Neutralization reaction

Where acid reacts with base, products have no property characteristics with either, making them ‘neutral’

Redox (Reduction-Oxidation) reactions

Reaction where electrons are transferred from on reactant to another

Oxidation

Loss of electron, molecule becomes more positive

Reduction

Gain of electrons, molecule becomes more negative

Oxidation number/state & rules

+or- # assigned to molecule
reflects ± character of atom

Monatomic - same as charge

Neutral & Polyatomic ions - hypothetical charge (dividing up electrons among atoms)

• sum all atoms neutral = 0

• sum of oxidation numbers in polyatomic = charge

Elemental form - 0

Nonmetals - usually negative, sometimes positive

Reaction b/n metal & acid or metal salt pattern

A + BX → AX+B

Zn (s) + 2HBr (Aq) → ZnBr2 (Aq) + H2(g)

Mn (s) + Pb(NO3)2(aq) → Mn(NO3)2(aq) +Pb(s)

Displacement Reaction

Reaction where ion in solution is displaced/replaced through oxidation of element

Activity Series

List of metals in order of decreasing ease of oxidation

Used to predict outcome of reactions b/n metals & metal salts/acids

Active vs. Noble metals

Metals most easily oxidized vs. stable metals that form compounds less readily

Concentration

Quantity of solute in solvent

Molarity

expresses concentration of solution as moles of solute in liter of solution

moles solute/volume of solution in L

Dilution

Process of creating a less concentrated solution by adding more solvent

Titration

Process of reacting solution of unknown concentration to known concentration

Standard Solution

Solution of known concentration

Equivalence Point

Point in titration where added solute reacts completely w/ solute present in solution

Indicator

substance added to a solution that changes color when added solute reacts w/ solute in solution

ex. acid/base indicator that changes based on pH

Chemical Reaction to do Work

work = force * displacement

Thermodynamics 1 Law

Energy cannot be created nor destroyed, only converted into different forms

System

Limited & well-defined part of the universe used to analyze energy changes

Surroundings

Everything that is outside studied system in thermodynamics

Open vs. Closed vs. Isolated system system

Energy & matter can be exchanged with surroundings vs. exchange energy but not matter vs. neither energy or matter is exchanged

Internal energy (E)

energy of system that is sum of all kenetic & potential energies of components of system

Endothermic

System absorbs heat delta H = positive

Exothermic

heat exists system delta H = negative

State Function

Property of system determined by specifying systems state/condition (ie. temp, pressure, etc.)

Enthalpy

internal energy + product of pressure & volume of system

Pressure-Volume work

work involved in expansion/compression of gases

Enthalpy of Reaction

Enthalpy change that accompanies reaction

Calorimetry

Measurement of heat flow

Heat Capacity

Minimum amount of heat for an object to increase temperature by 1 K or C

Molar Heat Capacity

Heat capacity of 1 mole of a substance

Specific Heat (Capacity)

Heat Capacity of 1 gram of substance

Hess’s Law

If reaction is carried out in series of steps, delta H for the overall reaction= sum of enthalpy changes for individual steps

Enthalpy/Heat of Formation

Enthalpy change that comes with formation of substance from most stable form of its component elements

Standard Enthalpy Change

enthalpy change when all reactants and products are in standard states

Standard Enthalpy of Formation

Change in enthalpy for reaction that forms 1 mol of compound from its elements w/ all substances in standard states

Bond Enthalpy

Enthalpy change needed to break particular bond when substrate is in gas phase

Fuel Value

Energy released when 1g of substance is combusted

Electromagnetic Radiation

Radiant energy, form of energy that has wave characteristics & propagates through vacuum at characteristic speed of 3.00 × 10^8 m/s (speed of light)

Wavelength

Distance b/n two adjacent peaks in wave

Wavelength Frequency

Number of complete wavelengths/cycles that pass at a given point each second

Quantum

Smallest increment of radiant energy that may be absorbed or emitted

Photoelectric Effect

Emission of electrons from metal surface induced by light

Photon

Smallest increment of radiant energy

Spectrum

Distribution among various wavelengths of radiant energy emitted/absorbed by object

Spectrum containing radiation only of specific wavelengths

line spectrum

Ground state

Lowest energy state of an atom

Excited state

When electron of atom is in higher energy state

Momentum

Product of mass & velocity of object

matter waves

describes wave characteristics of a moving particle

Uncertainty principle

there is an inherent uncertainty in the precision with which we can simultaneously specify the position and momentum of a particle

Wave functions

Mathematical description of an allowed energy state for electron in quantum mechanical model of atom

Probability/Electron density

Probability of finding an electron at any particulat point in an atom

Orbitals

Describe spatial distribution of electron density

Electron Shell

Collection of orbitals that have the same value of n

subshell

Set of orbitals that have the same n and l values

node

points where wave function changes

Radial Probability Function

Probability that electron will be found at a certain distance from nucleus

Angular Node/Nodal Plane

Plane where electron density in atom/a molecule = 0, both atomic orbital and molecular orbitals can have nodal planes

Degenerate

Orbitals w/ same energy

Electron spin

Electrons have intrinsic property that causes each electron to behave as if it were a tiny sphere spinning on its own axis

Spin magnetic quantum number

quantum number associated w/ electron spin, may have values of +1/2 or -1/2

Pauli Exclusion Principle

No two electrons in an atom can have the same set of 4 quantum numbers n, 1, m1, and ms

Electron Configuration

Way that electrons are distributed among various orbitals of an atom

Orbital Diagram

Representation of atomic orbital drawn as a box w/ one or 2 hald arross representing elctrons

Hund’s rule

when filling degenerate orbitals, lowest energy is attained when number of electrons having the same spin is maximized

Core electrons

Inner shell electrons

Valence Electrons

Outer shell electrons that are involved in chemical bonding

Transition elements/metals

elements in which d orbitals are partially occupied

Lanthanide/rare earth elements

Element where the 4f subshell is only partially occupied

Actinide Elements

Element where the 5f orbitals are only partially occupied

Representative Elements

Element form w/n s&p blocks of periodic table

Electromagnetic Radiation

radiant energy, form of energy that has wave characteristics and that propagates through a vacuum at the characteristic speed 3.00 × 10^8 m/s

3 observations of how electromagnetic radiation & atoms interact

1) emission of light from hot objects (blackbody radiation)

2) emission of electrons from metal surfaces on which light shines (photoelectric effect)

3) emission of light from electronically excited gas atoms (emission spectra)

Planck Constant (h)

6.626 × 10^-34 J-s

Spectrum

Distribution among various wavelengths of the radiant energy emitted or absorbed by an object