DAT - General Chemistry Flashcards

Terms Definitions
F-
Fluoride
H-
Hydride
Cu2+
Cuprous
ClO3--
Chlorate
SO4^2-
Sulfate
NO3-
NItrate
Units of Coulomb
J/V

(Joules/Volts)
Bronsted-Lowry Acid
Species that DONATES protons.
Gamma Decay
NO CHANGE

Emission of gamma-particles, which are HIGH energy photons. Carry NO charge and simply lower the energy of the emitting nucleus without changing the mass number or the atomic number.

Daughters A and Z is same as parents.
Sublimation
Solid to gas (e.g dry ice)
Types of Systems
1. Isolated
2. Closed
3. Open
Raoult's Law
Vapor-Pressure Lowering

When solute B is added to pure solvent A, the vapor pressure of A above the solvent decreases.

If the vapor pressure of A above pure solvent A is designated P-(A) and the vapor pressure of A above the solution containing B is P(A), the vapor pressure decreases as follows:

Delta P = P-(A) - P(A)
Titration
Procedure used to determine the molarity of an acid or base.

Accomplished by reacting a known volume of solution of unknown concentration with a known volume of solution of known concentration.
Bronsted-Lowry Base
Species that ACCEPTS protons.

e.g. NH3 and Cl-

Not limited to aqueous solutions.
Colligative Properties
Physical properties derived solely from the number of particles present, not the nature of those particles.
Isochoric?
∆V=0 (Same Volume) so work=0, ∆E=Q
What is the Ideal Gas Law?
PV=nRT
Neutralization Reactions
Specific type of double displacements which occur when an acid reacts with a base to produce a solution of SALT and WATER.
Calculating Half-life
(t 1/2) =

(1/2)^n

n = half-lives.
Critical Point
Tip between liquid and gas phases.

Temperature and pressure above which no distinction between liquid and gas is possible.
Boiling point
Temperature at which the vapor pressure of the liquid equals the external pressure.
Sigma Bond
When orbitals overlap head to head.
Dipole-Dipole Interactions
Polar molecules tend to orient themselves such that the positive region of one molecule is close to the negative region of another molecule.

Are present in solid and liquid phases but become negligible in gas phase.

Tend to have higher boiling points than nonpolar species of comparable weiht.
Molality =?
Molality = mol solute/ kg solvent
Ideal Gas Law
Combines the relationships outlined in Boyle's, Charles', and Avogadro's Principle to yield an expression which can be used to predict the behavior of a gas.

PV = nRT
R = 8.22 x 10-2 L-atm/(mol-K)
Delta H
To find enthalpy change, one must substract the enthalpy of the reactants from the enthalpy of the products.

delta H(rxn) = H products - H reactants

Positive H = endothermic
Negative H = exothermic
Polar Covalent Bonds
Bond is partially covalent and partially ionic.
Covalent bonding
Electron pair is shared between two atoms.

Atoms can share more than one pair of electrons. One, two, and three electron pairs are said to be joined by single, double, and triple bonds, respectively.

Can be characterized by bond length and bond energy.
Electrons
Carry a charge equal in magnitude but opposite in sign to that of protons.
Electron configuration
The pattern by which subshells are filled and the number of electrons within each principal level and subshell.

In electron configuration notatn, the first number denotes the principal energy level, the letter designates the subshell, and the superscript gives the number of electrons in that subshell.

e.g. 2p^4 = four electrons in the second (p) subshell of the second principal energy level.
In a galvanic Cells, the anode is labeled...
Negative
Charge of a single electron
1.602 x 10^-19 Coulombs
Atomic Radius
Equal to one-half the distance between the centers of two atoms of that element.

Atomic radius decreases across a period from left to right and up a given group.

Atoms with largest atomic radii will be located at bottom of groups, and in Group 1.
Triple Point
Intersection of the three lines is called triple point. At this temperature and pressure, unique for a given susbtance,....

All three phases are in equilibrium.
Ionization Energy (IE)
or Ionization potential, is energy required to completely remove an electron from a gaseous atom or ion.

Removing an electron always requires input of energy.

Ionization energy increases from left to right across a period and up a group.
Rate-determining step
Slowest step in a proposed mechanism, because overall reaction cannot proceed faster than that step.
Zero-order reactions
Has a CONSTANT rate, which is INDEPENDENT of the reactant's concentrations.

Thus rate law is: rate = k

Units = Msec-1
What is the hybridization and bond angle of a molecule with 4 electron domains?
SP3, 109.5˚
Mixed-order reactions
Has a fractional order; e.g., rate = k[A]^1/3
Molecular formula
Gives the exact number of atoms of each element in the compound, and is usually a multiple of the empirical formula.
Atomic Emission Spectra
Used as a fingerprint for the element.

Because each element can have its electrons excited to different distinct energy levels. When these electrons return to their ground states, each will emit a photon with a wavelength characteristic of the specific transition it undergoes.
A zero order reaction has the form...
r = k
The first law of thermodynamics is best summed in the two words:

a. energy constant
b. energy changing
c. energy increasing
d. energy decreasing
e. disorder constant
a. energy constant
Yields
Yield of a reaction is the amount of product predicted or obtained when the reaction is carried out.

It can be determined or predicted from the balanced equation.
In gamma decay, the atomic number and mass number
Remain unchanged
Isotope
For a nucleus of a given element with a given number of protons, the various nuclei with different numbers of neutrons.
In beta- decay, the atomic number (Z)...
increased by one
Chemical Kinetics
Study of the rates of reactions, the effect of reaction conditions on these rates, and mechanisms implied by such observations.
Equivalent Weight
Useful to define a measure of reactive capacity.

Equivalents = Weight of Compound / Gram Equivalent Weight

Gram Equivalent Weight = Molar Mass / n

n = either number of hydrogens used per molecule of acid in reaction, or the number of hydroxyl groups used per molecule of base in reaction.
Closed system
When it CAN exchange ENERGY, but NOT matter with the surroundings, as with a steam radiator
Azimuthal Quantum Number
- second quantum number or angular momentum
- designated by letter l
- Information about the SHAPE
- Refers to the subshells or sublevels that occur within each principal energy level.
- For any given n, the value of l can be any integer in the range of 0 to n - 1.
- Four subshells corresponding to l = 0, 1, 2, and 3 are known as the s, p, d, and f subshells.
- Maximum number of electrons that can exist within a subshell is given by equation 4l + 2.
What is the basic building block of matter, representing the smallest unit of an element?
An atom
Le Chatelier's Principle
Used to determine the direction in which a reaction at equilibrium will proceed when subjected to stress, such as change in concentration, pressure, temperature, or volume.
What is the mole ratio of this equation?
N2(g) + 3 H2(g) -> 2NH3(g)
1:3:2 Ratio
Calculation of Electromagnetic energy of photons
E = hc/wavelength

h = Planck's constant
c = velocity of light (3.00 x 10^8 m/s)
wavelength = wavelength of radiation.
Heat of vaporization
Enthalpy change of a liquid to gas, Delta H (vap).
Electron at Ground State
electron is in its lowest energy state.
(n + l) rule
Indication of which subshell is lower in energy and will fill first.

e.g. 3d, n = 3 and l = 2, so (n + l) = 5
Which of the following will effect Keq?

a. decrease in T
b. increase in T
c. decrease in P
d. A & B
e. A & C
d. A and B
Molecular Weight
Sum of the atomic weights (in amu) of the atoms in the molecule.
Ka x Kb = Kw = 1.0 x 10^-14
Remember this.
What is the expression for the equilibrium constant for the following reaction?

2 H2 + N2 --> 2 NH3
Solution:

Kc = [NH3]^2 / ([H2]^3[N2])

Note: remember that exponents of the concentrations of teh reactants and products are equal to their stoichiometric coefficients in the equilibrium expression, but NOT kinetic rate law.
NaF(aq) + Ba(NO3)2(aq) --> ?
Net Ionic Eqation for reaction:

2F- + Ba^2- --> BaF2
Pauli Exclusion Principle
No two electrons in a given atom can possess the same set of four quantum numbers.
Representative elements
- A elements, which have either s or p sublevels as outermost orbitals.
Reactant Concentrations in regards to Reaction Rate.
Greater the [reactants], the greater the number of effective collisions per unit time.

Therefore, the reaction rate will infrease for all but zero-order reactions.
What is the percent yield for a reaction in which 27 g of Cu is produced by reacting 32.5 g of Zn in excess CuSO4 solution?
Answer: 84%

Solution:
The balanced equation is as follows:
Zn + CuSO4 --> Cu + ZnSO4

Calculate the theoretical yield for Cu:
32.5 g Zn x (1 mol Zn/65 g) = 0.5 mol

0.5 mol Zn x (1 mol Cu/1 mol Zn) = 0.5 mol Cu

0.5 mol Cu x (64 g /1 mol Cu) = theoretical yield (32 g)

% yield = (27g/32g) x 100% = 84%
Three categories of Periodic Table
1. Metals (left side and middle)
2. Nonmetals (right side)
3. Metalloids or semimetals (along diagonal line between the two).
Energy Value of a Quantum
E = hf

h = proportionality constant known as Planck's constant = 6.626 x 10^-34 J-s.

f = (sometimes designated v) = frequency of radiation.
The oxide of a non-metal is?
An acid anhydride. Basic anhydrides are those metal oxides that react with water ex) K2O + H2O -> 2KOH
The second law of thermodynamics is best summed in the 6 words:

a. spontaneous processes experience an increase entropy.
b. spontaneous processes experience a decreased entropy.
c. disorder is constant and quiescent always.
d. disorder occurs during cool
a. Spontaneous processes experience an increase entropy.
Relation between EMF and the Equilibrium Constant (Keq)
Delta G = -RT ln Keq

Combining equations:

Delta G = -nFE = -RT ln Keq

OR

nFE = RT ln Keq
Percent Composition by Mass
Is the mass of the solute divided by the mass of the solution, multiplied by 100.
Four variables that define a gaseous samples
pressure (P), volume (V), temperature (T), and number of moles (n).

Pressure usually expressed in terms of atmospheres (atm)0 or millimeters of mercury (mm Hg or torr)

1 atm = 760 mm Hg = 760 torr

Volume in Liters or milliliters.

Temperature in Kelvin.
The element with the greatest electron affinity will be the better (oxidizing or reducing) agent?
Oxidizing - Oxidizing agents are reduced, meaning they gain electrons.
Le Chatelier's Principle: Changes in Pressure or Volume
In a system at constant temperature, a change in pressure causes a change in volume, and vice versa.

Change in pressure or volume in liquids/solids will have little or NO effect.

Reactions involving gases, however, may be greatly affected by changes in P or V, since they are highly compressible.

Pressure and volume are inversely related. Increase in pressure will decrease moles of gas present (decreasing volume).
A reaction is always spontaneous if....

a. change in gibbs free energy is zero
b. change in gibbs free energy is positive
c. change in gibbs free energy is negative
d. change in enthalpy is negative
e. change in entropy is negative
c. change in gibbs free energy is NEGATIVE
A vessel contains 0.75 mol of nitrogen, 0.20 mol of hydrogen, and 0.05 mol of fluorine at a total pressure of 2.5 atm. What is the partial pressure of each gas?
First calculate the mole fraction of each gas.

X(N2) = 0.75 mol/1mol

X(H2) = 0.20 mol/1mol

X (F2) = 0.05 mol/1mol

Then calculate the partial pressure:

P(A) = X(A)P(T)

P(N2) = (2.5 atm)(0.75) = 1.875 atm

P(H2) = (2.5atm)(0.20) = 0.5 atm

P(F2) = (2.5atm)(0.05) = 0.125 atm
Le Chatelier's Principle: Changes in Temperature
Heat can be considered as a product (exothermic rxn) or as a reactant (endothermic rxn).

Depending on reaction, if temp was increased or decreased, it would alter the equilibrium.
What are the written electron configurations for Nitrogen (N) according to Hund's rule?
Nitrogen = 1s^2, 2s^2, 2p^3
It has an atomic number of 7. According to hund's rule, the two s orbitals will fill completely, while the p orbitals will each contain one electron, all with parallel spins.
What is the molecular geometry of a molecule with 4 electron domains with 0 non-bonding e- pairs?
With 1 non-bonding e- pair?
With 2 non-bonding e- pairs?
0 -Tetrahedral
1 pair - Trigonal Pyramidal
2 pairs - Bent
Ka < 1, then pKa = ?
pKa > 1

smaller Ka = weaker the acid
therefore, the bigger the pKa the weaker the acid.
Maximum entropy is seen in a system when which of the following is occurring?

a. change in gibbs free energy is zero
b. change in gibbs free energy is positive
c. change in gibbs free energy is negative
d. change in enthalpy is negative
e. change in entr
a. change in gibbs free energy is ZERO.
If Kb = 1.0 x 10^-7, then what is the pKb?
1.0 x 10^-7, then pKb = 7
CaCO3(s) + 2HCl(aq) -> CaCl2 + H2O + CO2
Using 400g CaCO2(s)
What volume of 6M HCl is needed to completely react with 400g CaCO2(s)?
400g CaCO3 -> 4 mol CaCO3(s) -> 8 mol HCl
M=mol/V
V=mol/M
V= 8 mol HCl/ 6mol/L = 1.33 L HCl
/ 85
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