Glosario UNCChem /Estequiometría
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Estequiometría or Problemas resueltos
-
A
- aceleración
- Medida de la velocidad de reacción en el transcurso del tiempo. el
uso más común es el de la aceleración
debida a la gravedad cuya constante gravitacional es según la
situación terrestre de unos 9.8 m/s2.
- ácido
- Compuesto que cede iones H+ en solución.
- ácido,a
- Describe una disolución con una elevada concentración de iones H+.
- anión,es
- Iones con carga negativa (Cl-, SO4(2-))
- ánodo
- electrodo que cede electrones en las reacciones red-ox por oxidación.
- area
- Medida de una superficie epresada en unidades de longitud al cuadrado.
- asociatividad
- Una propiedad que compara un estado tal que: (A+B)+C=A+(B+C) y (A*B)*C=A*(B*C)
- atmósfera,s
- Unidad más común usada para medir presiones. Casi igual al bar y al Kg/cm2
- átomo
- El objeto más pequeño que reúne las propiedades de un elemento. Compuesto a su vez de electrones(carga -) en su corteza y de protones(carga +) y de neutrones en su núcleo
- número atómico
- Número de protones o de electrones en un elemento.
- número de Avogadro
- Número de molécules en un mol 6.023 * 1023 moléculas/mol.
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B
- base
- Sustancia que cede iones (OH-) en solución.
- básico
- Que tiene las propiedades características de un base
- átomo de Bohr
- Bohr hizo contribuciones significativas sobre el átomo. Descubrió la linea espectral--
la razón por la que sólo a ciertas longitudes de onda son emitidos cuando los átomos cambian de nivel.
- soluciones buffer o tampón
- soluciones que resisten los cambios en su pH, cuando se les añade pequeñas cantidades devácidos o bases.
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C
- catalyst
- Substance that speeds up a chemical process without actually
changing the products of reaction
- cathode
- Electrode where electrons are gained (reduction) in redox reactions.
- cationes
- Ion with a positive charge.
- central atom
- In a Lewis structure, usually the atom that is the most
electronegative.
- carga
- Describes an object's ability to repel or attract other objects.
Protons have positive charges while
electrons have negative charges.
Like charges repel each other while opposite charges, such as
protons
and electrons, attract one another.
- cambios quimicos
- Processes or events that have altered the fundamental structure of
something.
- ecuación químic
- An expression of a fundamental change in the chemical substances.
- closure
- A mathmatical term which says that if you operated on any two real
numbers A and B with
- +,-,* or /, you get a real number
- propiedades coligativas
- Properties of a solución that depend only on the number of particles
dissolved in it,
not the properties of the particles themselves. The
main colligative properties
addressed at this web site are boiling point
elevation and freezing point depression.
- combustión
- When substances combine with oxygen and release energy.
- commutativity
- A math property which states: A+B=B+A and A*B=B*A
- compuesto
- Two or more atoms joined together chemically, with covalent or ionic
bonds.
- concentración
- The amount of substance in a specified space.
- ácido conjugado
- A substance which can lose a H+ ion to form a base.
- base conjugada
- A substance which can gain a H+ ion to form an acid.
- enlace covalente
- When two atoms share at least one pair of electrons.
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D
- isótopo hijo
- In a nuclear equation the compound remaining after the parent
isotope (the original
isotope) has undergone decay. A compound
undergoing decay, such as alpha decay,
will break into an alpha particle
and a daughter isotope.
- decay
- Change of an element into a different element, usually with some
other particle(s)
and energy emitted.
- decimal
- The number of digits to the right of the decimal point in a number
- denso
- A compact substance or a substance with a high density.
- densidad
- Mass per unit volume of a substance.
- dipole-dipole forces
- Intermolecular forces that exist between polar molecules. Active
only when the
molecules are close together. The strengths of
intermolecular attractions increase
when polarity increases.
- fuerzas de dispersión (tambien llamadas fuerzas de dispersión de London)
- Dispersion is an intermolecular attraction force that exists between
all molecules.
These forces are the result of the movement of electrons
which cause slight polar
moments. Dispersion forces are generally very
weak but as the molecular weight
increases so does their strength.
- disociación
- Breaking down of a compound into its components.
- distributivity
- A math property which states: A*(B+C)=(A*B)+(A*C)
- enlace doble
- When an atom is bonded to another atom by two sets of electron
pairs.
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E
- efusión
- Movement of gas molecules through a small opening.
- electrochemical cell
- Gives an electric current with a steady voltage as a result of an
electron transfer reaction.
- electrodos
- Device that moves electrons into or out of a solución by conduction.
- electrólisis
- Changing the chemical structure of a compound using electrical
energy.
- electromagnetic spectrum
- Complete range of wavelengths which light can have. These include
infared, ultraviolet,
and all other types of electromagnetic radiation,
as well as visible light.
- electrón
- One of the parts of the atom having a negative charge. Indivisible
particle with a charge of -1.
- electron geometry
- Structure of a compound based on the arrangement of its electrons.
- electronegativity
- Measure of a substances's ability to attract electrons.
- electrostatic forces
- Forces between charged objects.
- elemento
- Substance consisting of only one type of atom.
- empirical formula
- Formula showing the simplist ratio of elements in a compound.
- endotérmico
- Reaction that absorbs heat from its surroundings as the reaction
proceeds.
- energia
- Ability to do work.
- entalpía
- Change in heat.
- entropía
- Measure of the disorder of a system.
- equilibrio
- When the reactants and products are in a constant ratio. The forward
reaction and
the reverse reactions occur at the same rate when a system
is in equilibrium.
- constante de equilibrio
- Value that expresses how far the reaction proceeds before reaching
equilibrium.
A small number means that the equilibrium is towards the
reactants side while a
- large number means that the equilibrium is
towards the products side.
- expresiones de equilibrio
- The expression giving the ratio between the products and reactants.
The equilibrium
- expression is equal to the concentration of each product
raised to its coefficient in a
balanced chemical equation and multiplied
together, divided by the concentrat ion
of the product of reactants to
the power of their coefficients.
- punto de equivalencia
- Occurs when the moles of acid equal the moles of base in a solución.
- exotérmico
- Reaction that gives off heat to the environment.
- exponentiation
- Raising something to a power.
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F
- fuerza
- An entity that when applied to a mass causes it to accelerate. Sir
Isaac
Newton's Second Law of mation states: the magnitude of a force =
mass * acceleration.
- electrones libres
- Electron which is not attached to a nucleus.
- free energy
- The energy of a system that is available to do work at constant
temperature and pressure.
- frecuencia
- Number of events in a given unit of time. When describing a moving
wave, means the
number of peaks which would pass a stationary point in a
given amount of time.
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G
- contador geiger
- Instrument that measures radiation output.
- ley de Graham
- The rate of diffusion of a gas is inversely proportional to the
square root of its molecular weight.
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H
- vida media
- The amount of time it takes for half an initial amount to
disintegrate.
- Heisenberg principio de incertidumbre
- This principle states that it is not possible to know a particle's
location and
momentum precisely at any time.
- hidrógeno, enlace de
- Strong type of intermolecular dipole-dipole atttraction. Occurs
between
hydrogen and F, O or N.
- hidrolisis
- When water reacts with another substance and as a result the oxygen
in
water makes a bond with the substance.
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I
- ideales ley de los gases
- PV=nRT
Describes the relationship between pressure (P),
temperature (T), volume (V),
and moles of gas (n). It is not completely
accurate, and becomes less accurate
- as conditions become less ideal.
- identidad
- A math property which states: A+0=A and A*1=A.
- intermoleculares, fuerzas
- Forces between molecules.
- intramoleculares, fuerzas
- Forces within molecules. Forces caused by the attraction and
repulsion of charged particles.
- inverso
- A math property which states: A+(-A)=0 and A*(1/A)=1
- ion
- Removing or adding electrons to an atom creates an ion (a charged
object very similar to an atom).
- ión-dipolo o dipolares, fuerzas
- Intermolecular force that exist between charged particles and
partially charged molecules.
- iónico, enlace
- When two oppositely charged atoms share at least one pair of
electrons but the electrons
spend more time near one of the atoms than
the other.
- ionización, energía de
- Energy required to remove an electron from a specific atom.
- ionizes
- When a substance breaks into its ionic components.
- isotopes
- Elements with the same number of protons but have different numbers
of neutrons,
and thus different masses.
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K
- kelvin
- The SI Unit of temperature. It is the degrees celsius plus 273.
- kinetic energy
- Energy an object has because of its mass and velocity. Objects that
don't move have
no kinetic energy. (Kinetic Energy=0.5*
mass*velocity2.
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L
- Le Chatlier's principle
- States that a system at equilibrum will oppose any change in the
equilibrium conditions.
- Lewis structures
- A way of representing molecular structures based on valence
electrons.
- limiting reagent
- The reactant that will be exhausted first.
- line spectra
- Spectra generated by excited substances. Consists of radiation with
only specific wavelengths.
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M
- mass number
- The number of protons and neutrons in an atom.
- mixture
- Composed of two or more substances, but each keeps its original
properties.
- molality
- The number of moles of solute (the material dissolved) per kilogram
of solvent
(what the solute is dissolved in).
- molar
- An term expressing molarity, the number of moles of solute/ liters
of solución
- molarity
- The number of moles of solute (the material dissolved) per liter of
solución.
- Used to express the concentration of a solución.
- mole
- A collection of 6.023* 1023 number of objects. Usually
used to mean molecules.
- molecular formula
- Shows the number of atoms of each element present in a molecule.
- molecular geometry
- Shape of a molecule, based on the relative positions of the atoms.
- molecular weight
- The combined weight (as given on the periodic table) of all the
elements in a compound.
- molecule
- Two or more atoms chemically combined.
- mole fraction
- The number of moles of a particular substance expressed as a
fraction of the total number of moles.
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N
- neutral
- An object that does not have a positive or negative charge.
- neutron
- A particle found in the nucleus of an atom. It is almost identical
in mass to a proton,
but carries no electric charge.
- nm
- An abbreviation for nano-meters. A nano-meter is equal to
10-9 meters.
- nucleus
- The central part of an atom that contains the protons and neutrons.
Plural nuclei.
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O
- octet
- In Lewis structures the goal is to make almost all atoms have an
octet.
This means that they will have access to 8 electrons regularly,
even if they
do have to share some of them.
- orbitals
- An energy state in the atomic model which describes where an
electron will likely be.
- oxidation number
- A number assigned to each atom to help keep track of the electrons
during a redox-reaction.
- oxidation reaction
- A reaction where a substance loses electrons
- oxidation-reduction-reaction
- A reaction involving the transfer of electrons.
- oxyacid
- When one or more hydroxide (OH) groups are bonded to a central atom.
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P
- parent isotope
- An element that undergoes nuclear decay.
- partial pressures
- The pressure exerted by a certain gas in a mixture.
- particle
- Small portion of matter
- percent composition
- Expresses the weight ratio between different elements in a compound.
- periodic table
- Grouping of the known elements by their number of protons. There are
many other
trends such as size of elements and electronegativity that
are easily expressed in terms of the periodic table.
- pH
- Measures the acidity of a solución. It is the negative log of the
concentration of the hydrogen ions in a substance.
- photons
- Massless packet of energy, which behaves like both a wave and a
particle.
- physical property
- A property that can be measured without changing the chemical
composition of a substance.
- pi bonds
- A type of covalent bond in which the electron density is
concentrated around the line bonding the atoms.
- Planck
- Planck contributed to the understanding of the electromagnetic
spectrum by realizing that the
relationship between the change in energy
and frequency is quantized according to the equation
delta E=hv where h
is Planck's constant.
- pOH
- Measures the basicity of a solución. It is the negative log of the
concentration of the hydroxide ions.
- polar molecules
- Molecule with a partial charge.
- potential energy
- The energy an object has because of its composition or position.
- pressure
- Force per unit area.
- principal quantum number
- The number related to the amount of energy an electron has and
therefore describing
which shell the electron is in.
- products
- The compounds that are formed when a reaction goes to completion.
- proportion
- An equality between two ratios.
- proton
- Particle found in a nucleus with a positive charge. Number of these
gives atomic number.
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Q
- quantum
- Something which comes in discrete units. Eg, money is quantized
(divided into units);
it comes in quanta (divisions) of one cent.
- quantum numbers
- Set of numbers used to describe an electron's position.
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R
- radiant energy
- Energy which is transmitted away from its source. eg, energy that is
emitted when
electrons transition down from one level to another.
- radiation
- Energy in the form of photons.
- radioactive
- Substance containing an element which decays.
- ratio
- The relative size of two quantities expressed as the quotient of one
divided by the other;
the ratio of a to b is written as a:b or a/b.
- reactants
- Substances initially present in a chemical reaction.
- reduction reaction
- A reaction in which a substance gains at least one electron.
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S
- salts
- Ionic compounds that can be formed by replacing one or more of the
hydrogen ions of
an acid with another positive ion.
- shells
- Where the electrons generally stay. There are 4 types of electron
shells: s, p, d and f shells.
- sigma bonds
- A type of covalent bond in which most of the electrons are located
in between the nuclei.
- single bond
- When an electron pair is shared by two different elements.
- SI Unit
- Stands for Systeme International d'Unites, a international system
which established a
0 uniform set of measurement units.
- solute
- What is dissolved in a solución eg, the salt in saltwater.
- solución
- Mixture of a solid and a liquid where the solid never settles out,
eg saltwater.
- solvent
- Liquid in which something is dissolved, eg the water in saltwater.
- specific heat
- The amount of heat it takes for a substance to be raised one degree
C.
- spontaneous reaction
- A reaction that will proceed without any outside energy.
- state property
- A state property is a quantity that is independent of how the
substance was prepared.
Examples of state properties are altitude,
pressure, volume, temperature and internal energy.
- states of matter
- Solid, liquid, gas and plasma. Plasma is a "soup" of diassociated
nuclei and electrons,
normally found only in stellar objects.
- stoichiometry
- The study of the relationships between amounts of products and
reactants.
- STP
- Standard temperature and pressure. This is 0oC and 1 atm.
- sublevel
- One part of a level, each of which can hold different numbers of
electrons.
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T
- term
- Each compound or element in a chemical equation.
- thermodynamics
- The study of heat and energy flow in chemical reactions.
- titration
- Reacting a solución of unknown concentration with a solución of a
known
concentration for the purpose of finding out more about the
unknown solución.
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V
- valence electrons
- The electrons in the outermost shell of an atom.
- van der Waals equation
- An equation for non-ideal gasses that accounts for intermolecular
attraction and the volumes occupied by the gas molecules.
- velocity
- Speed of an object; the change in position over time.
- volume
- Measures the size of an object using length measurements in three
dimensions.
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W
- wave
- A signal which propagates through space, much like a water wave
moves through water.
- wavelength
- On a periodic curve, the length between two consecutive troughs (low
points) or peaks (high points).
- weak acid
- Substances capable of donating hydrogen but do not completely ionize
in solución.
- weak bases
- Substances capable of accepting hydrogen but do not completely
ionize in solución.
- work
- Expression of the movement of an object against some force.
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