Chem class 2 Flashcards
explain the difference between σ and π
Sigma σ bonds are the result of end to end overlap of orbitals and make single bonds.
**Pi π ** bonds are the result of side to side overlap of open rules and result in double and triple bonds.
Sp hybridized carbon atoms
Have two groups bonded to them and have 180° bond angle between those groups
sp2
Carbon atoms have three groups bonded 120° apart
sp3
Carbons have four groups bonded 109.5° apart
Covalent bond
Is formed between atoms when each contributes one or more of its unpaired valence electrons. The electrons are shared by both atoms to help complete both octets.
Lewis base
Is a Nucleophile/ligand that donates a pair of electrons
Lewis acid
Except a pair of electrons and is a electrophile (electron loving)
Ionic bonds
Form between elements with large differences in electronegativity metals + nonmetals.
Strength of the bond depends on the charge and size of the ions, larger charges and smaller ions make the strongest ionic bonds.
what element can hydrogen bond
F, O, N
First law of thermodynamics
**The total energy of the universe is constant. **Energy may be transformed from one form to another, but it cannot be created or destroyed.
No transformation of energy is possible.
Thermodynamics
THE TRANSFORMATION OF ENERGY FROM ONE FORM TO ANOTHER.
Describe energy flowing in and out of the system
- When energy flows into a system from the surroundings, the energy of the system increases and the energy of the surroundings decreases.
- When energy flows out of a system into the surroundings the energy of the system decreases and the energy of the surrounding increases.
Enthalpy; H
Is a measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction that run at constant pressure.
When a bond is formed energy is released ∆H <0
Energy must be put into a bond to break it ∆H >0
∆H is know as HEAT of rxn
Exothermic
∆H is negative
**Products are in a lower energy state than reactants and the products have stronger bonds **
Endothermic
**∆H is positive
Products are in a higher energy state than the reactants and have weaker bonds.**
What contributes to the change in enthalpy of a chemical rxn?
Phase change
Formation of stronger intermolecular forces
Breaking covalent bonds
Standard conditions of temperature and pressure
298 K (25° C)
pressure is 1 atm
STP is 0°
Hess’s Law
A + B –> AB ∆H= - neg exo
Energy is released to make a bond
AB–> A + B ∆H= + pos end
Energy is needed to break a bond
Second law of thermodynamics
The disorder of the universe increases in a spontaneous process.
All processes tend to run in a direction that leads to Maximum disorder.
Entropy
The measure of disorder or randomness
S
∆S
Positive ∆S
I is when randomness increases or order decreases
AB–> A + B
Neg ∆S
If randomness decreases or order increases
A + B –> AB
Entropy rules
- Liquids have more entropy than solids
- Gases have more entropy than solids or liquids
- Particles in solution have more entropy than undissolved solids
- Two moles of a substance have more entropy than one mole
With the freezing of a liquid have a negative or positive ∆S?
negative
A gas undergoes condensation. What’s true about the process
∆H is negative and ∆S is negative
Third law of thermodynamics
Zero entropy. At absolute zero, thermal energy is absent and only the least energetic thermodynamics state is available to the system in question.
Lowest achievable temperature.
Gibbs free energy
∆G= ∆H-T∆S
∆G<0
Spontaneous in the forward direction
∆G>0
Nonspontaneous in the forward direction
∆G=0
Reaction is at equilibrium
-∆H +∆S -∆G
**Reaction is spontaneous **
+∆H +∆S -∆G
Reaction is spontaneous at high temperature
+∆H +∆S +∆G
Reaction is non-spontaneous at low temperature
-∆H -∆S +∆G
Reaction is non-spontaneous at high temperature
-∆H -∆S -∆G
Reaction is spontaneous at low temperature
+∆H -∆S +∆G
Reaction is non-spontaneous
Exothermic
Exergonic
negative
Products have lower free energy than reactants
Endothermic
Endergonic
Positive
Products have higher free energy than the reactants
Aside from mercury, why does all transition metal elements have higher melting points than Group I metals?
Transition metal elements can have both d and s electrons delocalized.
Metals readily absorb and conduct heat primarily because___________
the heat energy is absorbed by delocalized electrons as kinetic energy.
What is the shape of the nitrate ion?
Trigonal planar
An atom that has three groups of atoms and no lone pairs has a trigonal planar geometry.
What is the shape of the carbonate ion, CO3^2– ?
Trigonal planar
Coordination complexes
Coordination complexes are covalently bonded complexes between nonmetal ligands and a transition metal ion.
The shape of urea is
trigonal planar
Polar covalent bond has what characteristic?
ionic
