Chemistry Review Flashcards

Flashcards for reviewing Chemistry lecture notes.

Internal Energy Transfer

Energy transferred as heat when the system and surroundings are at different temperatures, or as work when an object is moved by a force.

Increase in Internal Energy

Heat absorbed by the system (q > 0) or work done on the system (w > 0).

What is the equation for the change in internal energy (ΔE)?

q + w

What does it mean to say that energy is always conserved?

Energy cannot be created or destroyed, only changed from one form to another or transferred into or out of a system.

What does it mean to say that the internal energy of a system is a state function?

The same overall ΔE can occur through any combination of q and w.

What occurs during work of expansion?

Increase in volume.

What occurs during work of contraction?

Decrease in volume.

What does it mean to say that Enthalpy (H) is a state function?

Independent of how the change occurred.

At constant P, what does the value of ΔH equal?

ΔE plus the PV work

What is qp?

The heat released or absorbed during a chemical or physical change that takes place at constant pressure.

What is the sign convention for ΔH in an exothermic process?

ΔH < 0

What is the sign convention for ΔH in an endothermic process?

ΔH > 0

How do we calculate ΔH of a process?

By measuring the energy transferred as heat at constant pressure (qp).

Specific Heat Capacity (c)

The quantity of energy needed to raise the temperature of 1 g of the substance by 1 K.

What does a coffee cup calorimeter measure at?

Constant Pressure.

What does a bomb calorimeter measure at?

Constant Volume.

Thermochemical Equation

Shows a balanced reaction and its ΔH.

What amounts are specified in a thermochemical equation?

The amount of substance and the quantity of heat are thermochemically equivalent and form a conversion factor for finding the quantity of heat transferred when any amount of the substance reacts.

Hess's Law

Determine ΔH of any reaction by assuming that it is the sum of other reactions.

Standard States

A set of specific conditions used for determining thermodynamic variables for all substances.

Standard Enthalpy of Formation (ΔH°f)

The enthalpy change when 1 mol of a compound forms from its elements with all substances in their standard states.

Nature of Light

Electromagnetic radiation that travels in waves characterized by a given wavelength (λ) and frequency (ν).

What is the relationship between wavelength and frequency?

Wavelength and frequency are inversely proportional to each other.

What does λ ν equal to?

Speed of Light (c)

What wavelengths is the visible region between?

Wavelengths 750 nm (red) and 400 nm (violet).

Refraction

Change in a wave’s speed when entering a different medium.

Diffraction

Bend of a wave around an edge of an edge of an object.

Quantum Theory

Light exists as photons (quanta) whose energy is directly proportional to the frequency.

According to quantum theory, what energy does an atom have?

An atom has only certain quantities of energy (E = nhv), and it can change its energy only by absorbing or emitting a photon whose energy equals the change in the atom’s energy.

What does light emitted by electrically excited atoms of elements and refracted through a prism appear as?

Appears as separate spectral lines.

Rydberg equation

Used to determine the wavelength of a spectral line.

Bohr's Proposal

An electron moves in fixed orbits.

What principal was Bohr correct on?

An atom’s energy is quantized.

Spectrometry

An instrumental technique that uses emission and absorption spectra to identify substances and measure their concentrations.

Wave-Particle Duality of Matter and Energy

Matter and energy are no longer viewed as distinct entities.

de Broglie wavelength

An electron (or any object) has wavelike motion.

Where is Wave-particle duality of matter and energy observable at?

Wave-particle duality of matter and energy is observable only on the atomic scale

Uncertainty Principle

We can never know simultaneously the position and speed of an electron.

Atomic Orbital (ψ, wave function)

A mathematical description of the electron’s wavelike behavior in an atom.

Schrodinger equation

Converts each allowed wave function to one of the atom’s energy states.

Name the three quantum numbers that describe an atomic orbital.

n (size), l (shape), and m1 (orientation).

Fourth Quantum Number (ms)

Describes the electron's spin.

l = 0

Spherical (s) orbital.

l = 1

Three two-lobed (p) orbitals.

l = 2

5 multilobed (d) orbitals.

l = 3

Seven multilobed (f) orbitals.

In the special case of the H atom, what do the energy levels depend on?

Only on the n value.

Pauli Exclusion Principle

Each electron in an atom to have a unique set of four quantum numbers.

How many electrons can an orbital hold?

No more than two electrons, and their spins must be paired (opposite).

List the electrostatic interactions determine sublevel energy.

1. Greater nuclear charge lowers sublevel energy, making electrons harder to remove. 2. Electron-electron repulsions raise sublevel energy, making electrons easier to remove. Repulsions shield electrons from the full nuclear charge, reducing it to an effective nuclear charge, Zeff. Inner electrons shield outer electrons very effectively. 3. Penetration makes an electron harder to remove because nuclear attraction increases and shielding decreases. As a result, an energy level is split into sublevels with the energy order s < p < d < f

Aufbau Principle

One electron is added to an atom of each successive element in accord with the Pauli exclusion principle and Hund’s rule.

Hund's Rule

Orbitals of equal energy become half-filled, with electron spins parallel, before any pairing of spins occur.

Valence electrons for main-group elements

Electrons involved in reactions are in the outer (highest energy) level only.

Valence electrons for transition metals

(n-1)d electrons are also considered valence electrons.

Because of shielding of d electrons by electrons in inner sublevels and penetration by the ns electron, the (n-1)d sublevel fills after what?

ns and before the np sublevels.

In Periods 6 and 7, what fills between the first and second (n-1)d orbitals?

(n-2)f orbitals fill between the first and second (n-1)d orbitals.

Elements within a group have what?

Similar outer electron configurations and similar chemical behavior.

Atomic Size

Half the distance between nuclei of adjacent atoms.

How does atomic size increase and decrease?

Increases down a main group and decreases across a period.

First Ionization Energy (IE1)

The energy required to remove a mole of electrons from a mole of gaseous atoms or ions.

How is First Ionization Energy (IE1) related to atomic size?

Inversely related to atomic size IE1 decreases down a main group and increases a period

Successive ionization energies of an element show what?

A very large increase after all valence electrons have been removed.

What does metallic behavior correlate with?

Large atomic size and low ionization energy.

How does metallic behavior increase and decrease?

Increase down a group and decrease from left to right across a period.

Why are Elements in Groups 1 and 2 strong reducing agents?

Lose electron readily.

Why are nonmetals in Groups 16 and 17 strong oxidizing agents?

Readily gain electrons.

Metal oxides are what?

Basic.

Nonmetal oxides are what?

Acidic.

How do oxides change across a period and down a group?

More acidic across a period and more basic down a group.

Many main-group elements form ions that are what?

Isoelectronic with the nearest noble gas.

Metals in Groups 13 to 15 what?

Lose either their np electrons or both their ns and np electrons.

Transition metals what?

Lose ns electrons before (n - 1)d electrons commonly and commonly form more than one ion

Why are Many transition metals and their compounds paramagnetic?

Atoms (or ions) have unpaired electrons.

Cations

Smaller than their parent atoms.

Anions

Larger than their parent atoms.

Ionic radius

Increases down a group.

Across a period, ionic radii what?

Generally decrease, but a large increase occurs from the last cation to the first anion.

What do Nearly all naturally occurring substances consist of?

Atoms or ions bonded to others.

Chemical Bonding

Allows atoms to lower their energy

Ionic Bonding

Metals atoms transfer electrons to nonmetal atoms, and the resulting ions attract each other and form an ionic solid.

Covalent Bonding

Most common between nonmetal atoms and usually results in individual molecules. Bonded atoms share one or more pairs of electrons that are localized between them.

Metallic Bonding

Many metal atoms pool their valence electrons into delocalized electron “sea” that holds all the atoms in the sample together

Lewis Electron-Dot Symbol

Shows valence electrons as dots surrounding the element symbol.

Octet Rule

Atoms lose, gain, or share electrons to attain a filled outer level of eight (or two) electrons.

In ionic bonding, what happens?

A metal transfers electrons to a nonmetal, and the resulting ions attract each other to form a solid.

Main-group elements what?

Often attain a filled outer level (either eight electrons or two electrons) by forming ions that have the electron configuration of the nearest noble gas

Ion formation by itself what?

Absorbs energy, but more than that quantity of energy is released when the ions form a solid.

High Lattice Energy of an Ionic Solid

The energy required to separate the solid into gaseous ions.

Lattice Energy

Determined by applying Hess’s law in a Born-Haber cycle

Lattice Energies

Increase with higher ionic charge and decrease with larger ionic radius (Coulomb’s law)

Ionic solids are what because of strong electrostatic attraction that keep ions in position?

Hard, conduct a current only when melted or dissolved, and have high melting and boiling points.

Ion pairs form when what?

In an ionic compound vaporizes

Covalent Bond

A shared, localized pair of valence electrons holds the nuclei of atoms together in a covalent bond, filling each atom’s outer level.

Bond Order

The number of shared paris between two atoms.

Bond Energy (strength)

The energy absorbed to separate the atoms; the same quantity of energy is released when the bond forms.

Bond Length

The distance between the nuclei of two atoms

For a given pair of atoms, bond order is what?

Directly related to bond energy and inversely related to bond length.

Molecular covalent substances

Soft and low melting because of the weak forces between the molecules, not the strong bonding forces within them.

Network covalent solids

Hard and high melting because covalent bonds join all the atoms in the sample.

Most covalent substances what?

Have low electrical conductivity because their electrons are localized and ions are absent.