MCAT Chemistry Flashcards
Which particle is more massive: proton or neutron?
Neutron
What is an element’s MASS NUMBER?
sum of the protons and neutrons
What is the symbol, i.e. letter, for MASS #?
A
what is an atomic mass unit? Specifically, what is its actual definition?
What is it’s numerical value?
Unit used to describe the mass of atoms, molecules, and particles. One amu is exactly one-twelfth the mass of a carbon-12 atom, which is ~ 1.66 x 10-24 grams (g)
[Kaplan mcat gen chem]
what is the unit for atomic mass?
amu
what is ‘atomic mass’?
mass of an atom compared to mass of carbon-12 atom
What is ‘atomic weight’ or ‘molecular weight’?
weight, in grams, of 1 mole of an atom or molecule
[NOTE: Kaplan treats atomic mass & atomic weight as two different terms, while EK and college chem textbook uses them interchangeably]
what is another name for an ‘a.m.u.’?
dalton
What is the SI abbreviation for an amu?
u
what is another name/term for atomic weight?
Molar mass
What is a mole?
(What substance in nature is the mole based on?)
It’s the number of particles in a 12-gram sample of carbon-12.
In a periodic table, which groups are called the “periods”? Are the columns referred to as periods, or are the horizontal rows referred to as periods?
Horizontal rows
What is each vertical column in a periodic table called?
Each column called be called a ‘group’ or ‘family’
What are the three main categories that all the elements can be grouped into?
Metals,
non-metals, and
metalloids
What are metalloids?
Elements that share the characteristics of metals and nonmetals
How many groups are there in the periodic table?
18
What 4 characteristics of metals should u know for MCAT (according to EK)?
Metals are:
lustrous,
malleable,
ductile,
and thermally and electrically conductive
What does ‘malleable’ mean?
Easily hammered into thin strips
what does ductile mean?
Easily stretched, easily drawn into wires
Which group are the alkali metals?
Group 1
which group # are the alkaline earth metals?
2
which group # are the halogens?
17
in the periodic table, how is the atomic mass for element determined/derived?
The atomic mass for a given element in the table is actually the weighted average of all the naturally occurring isotopes of the element
What are transition metals??
Groups 3-12 on the periodic table
What are chalcogens?
Group 6A (group 16) elements
what are the most famous of the chalcogens?
Oxygen and sulfur
which of the noble gases are liquid at room temp?
none
True/False:
the mnemonic I Brought Clothes From Old Navy Home refers to the halogens
False!
I, Br, Cl, F are halogens, but O, N, and H are NOT halogens! However, all of these are diatomics!
Do larger or smaller atoms make stronger pi bonds?
Smaller atoms (p. 5, EK Chem)
When transition metals form subshells, which subshell loses electrons first?
S subshell
After the s subshell of a transition metal loses electrons, which subshell loses electrons next?
D subshell
What law/equation do you use to find the force exerted by the nucleus on the outermost electron?
Coulomb’s law
How do you write Coulomb’s law as an equation?
F = *k ** q1 * q2
r2
Do ions with the same exact # of electrons have increasing or decreasing radii as the Z of the nuclei increase?
Decreasing radius with increasing Z, given that the # of electrons stays the same for all the elements being compared
What is Zeff?
Effective nuclear charge
What is effective nuclear charge?
the net positive charge experienced by an outer electron in a multi-electron atom.
What is the equation for Zeff?
Zeff = Z − S
where:
Z is the number of protons in the nucleus (atomic number)
S is the average number of electrons between the nucleus and the electron in question (the number of nonvalence electrons).
How do you use Zeff?
Plug in Zeff for one of the q values, rather than plugging in the actual # of protons
In the periodic table, Zeff (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
Increases,
increases
In the periodic table, Atomic radii (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
(p. 7, EK)
Increases,
decreases
what is the name given to the energy required to detach an electron from a neutral atom in the gaseous state?
Ionization energy
X + energy → X+ + e-
In the periodic table, ionization energy (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
Decreases, increases
What is electronegativity?
The tendency of an atom to attract an electron and thereby form a bond with another atom
What is the name given to the system that’s used to measure electronegativity?
the Pauling scale
What is the highest electronegativity value?
4 (or sometimes 4.1)
which element(s) have the highest electronegativity?
F
What are the electronegativity values for the noble gases?
The noble gases have no electronegativity value
In the periodic table, electron affinity (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
decreases,
increases
How does ‘dipole moment’ relate to electronegativity?
The greater the difference in electronegativity between 2 bonded atoms, the greater the dipole moment
In the periodic table, metallic characteristics (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
increase,
decrease
What is a dipole moment?
Dipole moment is the measured polarity of a polar covalent bond.
Dipole moment refers to the quality of a system to behave like a dipole.
What is electron affinity?
X + e− → X− + energy
3 definitions:
1:
The energy released when an electron is added to a NEUTRAL atom that is in a gaseous state. (EK chem)
2:
EA is the amount of energy required to detach an electron from a singly charged negative ion;
An equivalent definition is the energy released when an electron is attached to a neutral atom or molecule. (wiki)
3:
EA is the energy change that occurs when an electron is added to a gaseous atom. EA represents the ease with which the atom can accept an electron. (suhail’s Kaplan p 25)
What is the relationship between Zeff and EA?
Direct relationship
In the periodic table, electron affinity (increases/decreases) going from top to bottom and (increases/decreases) going from left to right.
decreases,
increases
How many base units are there in the SI system?
7
list the 7 quantities being measured by the 7 base units of the SI system:
amount,
electric current,
length,
luminous intensity,
mass,
temperature,
time
What SI unit measures time?
second
which What SI unit measures temperature?
Kelvin
Which SI unit measures mass?
Kilogram
What SI unit measures luminous intensity?
Candela
What SI unit measures length?
meter
What SI unit measures electric current?
Ampere
What SI unit measures amount?
mole
What amount does the prefix Mega- denote?
106
What amount does the prefix Kilo- denote?
103
What amount does the prefix Femto- denote?
10-15
What amount does the prefix nano- denote?
10-9
What amount does the prefix pico- denote?
10-12
What amount does the prefix Deci- denote?
10-1
What amount does the prefix Micro- denote?
10-6
What amount does the prefix Centi- denote?
10-2
What amount does the prefix Milli- denote?
10-3
What is the difference between a molecular formula and an empirical formula?
Empirical formula only shows the lowest ratios between the atoms in the molecule;
molecular formula shows the actual number of atoms in the molecule
What’s up the suffixes –ic and –ous for Cations?
If an element can have more than one ionization state, the -ic was used for the cation with the greater positive charge, -ous for the cation with the **lesser **positive charge.
What’s up with the suffix –ic and –ous for Polyatomic Anions?
Polyatomic anions that come in multiple varieties are named depending on how many oxygens they have.
Which PAIs are named *–ate *and which are named -ite?
“-ate” is given to the PAI with more oxygens, -ite for the PAI with less
order the anion suffixes/prefixes from least oxygens to most:
per- , -ite, -ate, hypo-
hypo-ite,
- ite,
- ate,
per-ate
what is theoretical yield?
Amount of product made when a reaction runs to completion
what is the percent yield formula?
Why is the percent yield formula used?
In reality, a reaction may not run to completion before stopping. So the actual yield of a product will be less than the theoretical yield.
Formula for % yield is:
(actual yield/theoretical yield) * 100 = % yield
What does it mean when the symbol delta (∆) is present above the reaction arrow in a reaction equation?
delta means that heat is added to rxn
what does it mean when you see a reaction equation with two parallel arrows pointing in opposite directions?
It means the rxn can reach equilibrium
What does it mean when you see this symbol ∩ in a reaction equation?
It represents resonance structures
What are the two basic types of solids?
Crystalline and amorphous
What’s the difference between a crystalline solid and an amorphous solid?
Crystalline solids have a specific melting point, and a well-ordered structure of repeating units. These repeating units can each be atoms, molecules, or ions.
Amorphous solid can melt over a temperature range and has no repeating molecular structure.
What are polymers?
Solids that have repeating structural units at the molecular level, BUT can be amorphous solids or crystalline solids.
what determines whether a polymer is made into an amorphous solid or a crystalline solid?
Usually, rapid cooling of liquid polymers results in amorphous solids, slow cooling results in crystalline solids
what are biological examples of polymers?
DNA,
glycogen,
protein
what is ‘bond length’?
average distance between two nuclei in a bond, at which distance the potential energy of the system will be the lowest (an equilibrium between the tug of war created by like and unlike electrical charges)
what are the 4 types of crystals?
Ionic,
network,
metallic, and
molecular
what are network crystals?
they consist of an infinite network of atoms,
held together by polar and nonpolar bonds.
They are made up of atoms sharing their valence electrons.
what are examples of a network crystal?
Diamond,
graphite,
swarovski glass crystal (not like regular glass, which is also silicon dioxide but is an amorphous solid)
what are ionic crystals?
Solids that have oppositely charged ions held together by electrostatic force
what are metallic crystals?
Single-element metal solids that are held together by delocalized electrons
What are ‘molecular crystals’?
solids whose atoms/molecules are held together by weak intermolecular forces
molecular crystals are solids whose atoms/molecules are held together by weak intermolecular forces
what are the above weak intermolecular forces collectively called?
Van der Waals forces
What kinds of Van der Waals forces are there?
Hydrogen bonds,
dipole-dipole forces,
dispersion forces
(http://www.utas.edu.au/sciencelinks/chemincon/files/s1_grow/s1_soils/bonding/index.html#molecular)
In an atom, what is the name of the number assigned to each primary ‘energy level’ or ‘shell’ of electrons?
Principal quantum number
What is the symbol for the principal quantum #?
n
what is the symbol for the azimuthal quantum number?
ℓ
(lower case L)
which LETTER is assigned to label the first shell, or first energy level?
K
What are the letters that follow K?
I.e., what are the letters assigned to the 2nd, 3rd, 4th shells?
L, M, N
What is the overall term/name of the mini-levels within each shell?
Subshell or
sublevel
what is the term/name of the number assigned to each subshell?
Azimuthal quantum number
how many subshells or sublevels exist for the known atoms/elements?
4
what are the names/terms (letters) assigned to these subshells or sublevels?
s
p
d
f
What is the formula that tells you the MAXimum # of electrons that can fill a given shell/energy level?
2n2
What is the equation that tells you the relationship between azimuthal quantum number and principal quantum number?
ℓ = n - 1
what is the name of an area within the atom where an electron can probably be found?
orbital
what is the relationship between an orbital and a sublevel?
Orbital is the subdivision of a sublevel
What is the Heisenberg principle?
It is impossible to know both the position and momentum of an electron at the same time
how many electrons does an orbital hold?
2
what is the Magnetic quantum number?
name of the number assigned to an orbital
what is the number assigned to each individual electron in an atom?
Electron spin quantum number
what is the symbol for an electron spin quantum number?
ms
What is the Pauli exclusion principle?
no two electrons can have the same four quantum numbers
what are the possible electron spin quantum numbers?
1/2
and
-½
what is the Aufbau principle?
A lower-energy subshell is completely filled, before electrons are placed in the next, higher subshell.
What is Hund’s rule?
In the same subshell, Electrons will not completely fill any orbital until:
1: All the orbitals within that subshell contain at least one electron, AND
2: the unpaired electrons in the subshell have parallel spins
when talking about electron spins, what does it mean to say that 2 electrons have ‘parallel’ spins?
They have the same spin (such as ½ and ½, or -1/2 and -1/2)
Why do electrons follow Hund’s rule? Why do electrons prefer empty orbitals to half-filled orbitals? (Kaplan gen chem. Page 30)
Because a mutual repulsion must be overcome for 2 electrons with like charges to exist in the same orbital.
What was Planck’s quantum theory?
EM energy is quantized/discontinuous.
EM energy comes in discrete bundles / units / packets that are related to the frequency of the EM wave.
How is Planck’s quantum theory explained in equation form?
E = hf
What is de Broglie’s formula?
λ = h/mv
what did de Broglie’s equation show?
Electrons and other moving masses exhibit wave characteristics
what phenomenon in nature showed us that light is made up of photons?
The photoelectric effect
who’s famous for the photoelectric effect?
Einstein
specifically, how was the photoelectric effect observed? What specific phenomenon was used by Einstein to demonstrate the photoelectric effect?
Light shining on a metal causes the emission of electrons
how does the photoelectric effect demonstrate the quantized nature of EM?
Einstein showed that light is made up of particles
with regards to the photoelectric effect, what is the ‘work function’?
the work function of a metal is the minimum amount of energy required for the metal to eject an electron when it is hit by a photon
what is the symbol for the work function?
Φ
In the Photoelectric effect, what formula shows us the KE of the ejected electron?
KE = hf - Φ
what is hf in the work function formula?
The KE of the photon that ejected the electron
what are the exact values for temp and pressure at STP?
0 deg Celsius,
1 atm
at STP, what is the avg distance between gas molecules? (EK, p 23)
35 angstrom
what is the mean free path?
Distance traveled by a gas molecule between collisions
what is the mean free path of oxygen at STP?
1600 angstrom
can a nonpolar gas and a polar gas mix homogeneously?
YES
Gas can mix regardless of polarity differences
can gases of different densities possibly separate according to their density? [WITHOUT centrifuges]
If temp is low enough, gravity can cause denser (colder) gases to settle beneath less dense gases
what is the name of the concept/theory that relates to ideal gases?
Kinetic Molecular Theory of Gases
describe an ‘ideal gas’ as put forward by the Kinetic Molecular Theory.
(hint: there are 4 characteristics)
(p. 24, EK chem)
gas molecules have zero volume;
gas molecules exert no forces of attraction or repulsion towards each other;
gas molecules make completely elastic collisions with each other and their container, thus neither gaining nor losing any energy;
the avg kinetic energy of gas molecules is directly proportional to the temperature of the gas.
what is the ideal gas law? Give the equation.
PV = nRT
What is P in the equation for ideal gas law?
Pressure
what is the unit for P (ideal gas law)?
atm
What is the V in the ideal gas law equation?
Give the unit, too.
Volume,
in Liters
what is n, in the ideal gas law eqn?
of moles of gas
what is T, in the ideal gas eqn?
give the unit.
Temperature in Kelvin
what is R in the ideal gas eqn? give the unit
the universal gas constant
(0. 08206 L*atm*K-1*mol-1 or
8. 314 J*K-1*mol-1)
what is the meaning of the term ‘standard molar volume’?
the volume that all gases will have at STP, IF …
they are acting as IDEAL gases
All gases will have the same volume, if they have the same ______, ______, and _______.
temperature,
pressure, and
of molecules