Chem 17 (Lec) Reviewer /*Disclaimer: Sorry if may ibang maling stuff : (( Read the book na lang, it’s more accurate HAHA okay yun lang GOODLUCK SA EXAM <3 if may tanong rin, wala po akong alam sa chem 17 sorry di po ako ang tamang tanungan :D */
q=mc ∆ T where q is the quantity of heat, m is the mass of substance, c is the specific heat and
∆ T is the temperature change.
qsystem =
~*~*~*~*~*~*~ I.
Thermochemistry
Thermochemistry – reaction involving heat (also interacts with surroundings)
Law of conservation of energy!! The heat gained by a system is lost by its surroundings :D
Enthalpy ( ∆ H) – heat change associated
Calorimetry
with a given chemical reaction
heat of reaction (qrxn)- quantity of heat exchanged between a system and its surroundings when a chemical reaction occurs within system at CONSTANT TEMPERATURE.
+
ENDOTHERMIC
Heat is ABSORBED
EXOTHERMIC
Heat is RELEASED
∆ H -
∆ H
Bomb calorimeter- measures the heat evolved in a combustion reaction (an isolated system) Work (w):
w = -P ∆
Types of systems: Closed System Open System Isolated System
Can exchange ENERGY only Can exchange BOTH matter and energy Does not interact with surroundings
Energy (U) – capacity to do work
∆ U = q
1 atm L = 101.325 J **Ideal gas equation can be helpful in getting the volume
PV=nRT
Work (w) – force acting through a distance Heat- energy transferred between a system and its surroundings as a result of a temperature difference. Heat Capacity - the quantity of heat required to change the temperature of a system by one degree
1 cal = 4.184 J
First Law of Thermodynamics: The energy of an isolated system is constant.
U=q+w
+q - q
Heat is gained by the system Heat is released by the system © jgnoche 2015
+w -w
In phase transitions: (exchange of heat can be carried out reversibly)
Work is done to the system Worrk is done by the system
State Function – has a value that depends only on the exact condition or state in which a system is found and not on how that state was reached (not path dependent!) (ung mga capital letters like H, U, G, and S (HUGS!!) are state functions, unlike q and w na small letters lang) “Hess’s Law : if a process occurs in stages or steps, the enthalpy change for the overall process is the sum of the enthalpy changes for the individual steps” -
When a process is reversed, enthalpy reverses sign When the coeffecients are multiplied by n, the enthalpy is also multiplied by n. ( ∆ H is an extensive proerty)
II.
You just add all the
∆ H of the
individual steps. MAKE SURE THE EQUATIONS ARE BALANCED!!!!!! Spontaneous Changes: Entropy and Gibbs Free Energy
Spontaneous process – process occurs in a system left to itself. -
-
that
If a process is spontaneous, the reverse is nonspontaneous Nonspontaneous processes require the system to be acted on by an external agent Some spontneous occur very slowly and some very rapidly
Entropy (S) – the thermodynamic propert related to the way in which the energy of a system is distributed among the available microscopic energy levels. ‘Pag mas Entropy :))
magulo,
mas
mataas
ang
∆ S=
∆H T
Trouton’s rule: (may be used for most liquids)
87
∆ H vap kJ = mol T boiling pt .
Increase in entropy if: -
Liquid or solutions are formed from solids Gas are formed from solids or liquids Number of gas molecules increases Temperature increases
Third Law of Thermodynamics: the entropy of a pure perfect crystal at 0 Kelvin is zero. Gibbs Energy ( ∆ G)
∆ G=∆ H−T ∆ S
∆ G
The process is spontaneous
<0
∆ G
The process is nonspontanous
>0
∆ G
The process is at equilibrium
=0
Criteria for spontaneous change:
∆
∆
∆
H -
S +
G -
Result Spontaneous at all temperatures © jgnoche 2015
-
-
-
Spontaneous at low temperature Nonspontaneus at high temp Spontaneous at high temp Nonspontaneous at low temp nonspontaneous at all temp
+ +
+
+
+
-
+
Rate = k[A]m[B]n
(coeffecients
≠
exponents) k is the rate constant, and the larger its value, the faster a reaction goes. If exponent is 1, reaction is first order. If 2, second order... and so on -Zero order: there is no effect on the initial rate of the reaction
∆ G=∆ G° −RT ln Q
-First order- initial rate of reaction doubles
∆ G °=−RT ln K
-Second order-the initial rate of the reaction quadruples
ln
K 2 −∆ H ° 1 1 = − K 1 8.314 ( R ) T 2 T 1
(
)
-Third order- the initial rate of the reaction increases 8x.
Coupled reactions- combining a pair of
∆ G and one
reactions, one with a positive with
negative
∆ G,
to
obtain
a
Zero-order Reactions A
→
products
Rate = k[A]0 = k = constant
spontaneous overall reaction.
[SEE Ellingham diagram in the lab reviewer] III.
Chemical Kinetics (Ch. 14)
Rate of reaction Given the reaction: aA + bB
[A]t = -kt + [A]o First-Order Reactions
→ gG + hH
(negative pag products kasi nagdidisappear sila poof) The Rate Law (Effect of concentration on reaction rates) The rate of the reaction above is:
ln [A]t = -kt + ln [A]o © jgnoche 2015
Second-Order Reactions
HALF 1/[A] LIFE!!!t
= kt + 1/[A]o
Zero-order
2) Transition State Theory
t1/2 =
[ A ]o 2k
t1/2 =
0.693 k
The hypothetical species that is believe to exist in a transitory state that lies between the reactants and products.
First Order
Second-order
t1/2 =
1 k [ A ]o
(makikita ang transition state sa peak ng graph (reaction profile) above) Arrhenius Equation
ln k =
−Ea RT
+
A is the collision frequency R= 8.314 J/mol K Ea is the activation energy
ln
K2 K1
=
Ea 1 1 − R T1 T2
(
)
Reaction Mechanisms (page 658)
Theoretical Models for Chemical Kinetics: 1) Collision theory Only a fraction of collisions produce reaction Activation Energy, Ea
1) 2) 3) 4)
Elementary Process Steady State approximation Pseudo-order reactions Application: smog and kinetics of environments
Catalysis 1) Homogenous Catalysis – all species in the reaction are in solution © jgnoche 2015
2) Heterogeneous Catalysis – the catalyst is in the solid state. Reactants from gas or solution phase are adsorbed. Active sites on the catalytic surface are important.
IV.
Chemical Equilibrium (Ch. 15) aA + bB
↔ cC + dD
rate forward = rate reverse rate forward = k[A]a[B]b rate reverse = k[C]c[D]d
k 1 [C ]c [ D]d = =K eq k 2 [ A ]a [B] b
attaining a new equilibrium that partially offsets the impact of the change. Recall:
∆ G °=−RT ln K
V.
Acid- Base Equilibrium (Ch. 16)
Acids and bases Arrhenius Theory- Acids give of H+ while bases give of OH-. However, this did not handle non OH- bases like NH3. Bronsted-Lowry Theory- Acids are proton donor. Bases are proton accepter. Lewis Theory- acids are species that accept electron. Bases donate electron pair.
Kc for molar concentrations
Autoionization of Water
Kp for gases partial pressure
H 2O
(l)
+ H 2O
(l)
↔ H3O+ (aq) + OH- (aq)
Kw = 1.0 x 1014 = [H3O+][OH-]
RT ¿ ¿ K p=K c ¿
K >>1 products are favored K <<1 reactants are favored
[H3O+] = [OH-] =1.0 x 107 *pH = -log[H3O+] pH of water = 7 (K varies depending on temperature, thus, pH also varies. PERO that doesn’t mean na nagiging acidic/basic ang water at some temperature. Neutral siya lagi pero nagiiba lang ung pH range YAY)
Factors affecting equilibrium: 1) Concentration 2) Pressure/volume 3) Temperature **catalyst does not effect equilibrium Le Chatelier’s PrincipleWhen an equilibrium system is subjected to a change in temperature, pressure or concentration of reacting species, the system responds by
For conjugate acids or bases:
K w =K a K b pH of salt solutions: © jgnoche 2015
-
Salts of strong acids and srong bases do NOT hydrolyze pH = 7 Salts of strong bases and weak acids hyrdolyze. pH > 7 Salts of strong acid and weak base hydrolyze. pH < 7 Salts of weak acids and weak bases depends on Ka and Kb.
Factors affecting Solubility 1) 2) 3) 4) 5) 6)
Common ion effect Ionic strength Ion-pair formation Simultaneous equilibria Fractional precipitation pH
Strong Acids: HCl, HBr, HI, H2SO4, HClO4, HClO3, HNO3 Strong Bases: LiOH, NaOH, KOH, RbOH, CsOH, Mg(OH)2, Ca(OH)2, Sr(OH)2, Ba(OH)2, Common ion effect- describes the effect on an equilibrium by a second substance that furnishes the ions that can participate in that equilibrium. Buffer Solutions- two-component systems that change pH only slightly on addition of acid or base. The two components must not neutralize each other but must not neutralize strong acids and bases.
Molar solubility (s) =
√
m+ n
VII.
K sp mm n n
Complex Ions and Coordination Compounds (Ch. 24)
Recall the theories we studied: Valence bond shells lang yung reactions
theory – outermost nagpaparticipate sa
VSEPR – bond angles formed depend on lone pairs and bond formed (geometries) Hybridization – valence shells orbitals are hybridized to accommodate more electrons
Buffer Capacity - Amount of acid or base that a buffer can neutralize before its pH changes appreciably. Maximum buffer capacity exists when [HA] and [A ] are large and approximately equal to each other. Buffer Range
± 1 pH units around pKa
Werner’s Theory of coordination compounds- metal ions have two types of valency-primary and secondary, where the primary valency is said to be satisfied by negative ions only, and the secondary valency can be satisfied by positive ligand, negative or neutral molecule.
*higher concentration, higher buffer capacity Acid-base Indicators Neutralization Reactions and Titrations
VI.
Solubility (Ch. 18)
/* wala masyado dito kasi special form of equilibrium lang naman ang solubility (and mas maraming calculations than terms) :D*/
Ligands- lewis bases (meaning they donate electron pairs to central metal atoms) Monodentate ligand- uses one pair of electrons to form one point of attachment to the central metal atom or ion Bidentate ligand- uses two pairs of electrons to form one point of attachment to the central metal atom or ion. (e.g. ethylenediamine) © jgnoche 2015
Isomerism
Isomers (compound of the same chemical formula but with different properties) If di pa rin masyadong maget nomenclature, this one’s helpful:
yung
Structural Isomers (atoms are connected differently) Ionization Isomers (give different ions in solutions) Coordination (different ligand sets in anions and cations) Linkage (same ligand connected by different atoms)
Stereoisomers (same number and types of ligands; differ in the postion in space) geometric (diastereomers) (different arrangement around a metal ion cis/trans) optical (enantiomers) (nonsuperimpo sable mirror images)
Crystal Field Theory- bonding in a complex ion is considered to be an electrostatic attraction between the positively charged nucleus of the central metal ion and electrons in ligands. Focuses on the repulsions between ligand electrons and d electrons of the central ion. Splitting in octahedral complex ion:
© jgnoche 2015
ALL SQUARE PLANAR COMPLEX IONS ARE LOW SPIN (because square planar splitting is maximum) Magnetic Properties (Page 1088) Color
∆ o depends if ligands are weak field or
Acid-Base Reactions of Complex ions
strong field. VIII. To classify the ligands, the spectrochemical series is used:
Electrochemistry (Ch. 20)
Terms: Anode- electrode where oxidation occurs Cathode- electrode where reduction occurs
Weak field ligands are referred to as high spin whereas strong field ligands are referred to as low spin.
Cell diagram:
Splitting in tetrahedral complex ion:
ALL TETRAHEDRAL COMPLEX IONS ARE HIGH SPIN (because the tetrahedral splitting is small)
Splittin in square planar complex ion:
*take note of the flow of electrons Two kinds of electrochemical cells: 1) Galvanic or Voltaic cell- Spontaneous 2) Electrolytic Cellnonspontaneous (requires a power source)
∆ G °=−nF E ° cell F= 96 485 C/mol eNernst Equation:
Ecell =E ° cell−
0.0592 logQ © jgnoche 2015 n
RECOA – Reduction Cathode // Oxidation Anode Additional notes: E°cell is 0 for concentration cells. GEROA – Gain Oxidizing Agent
of
LEORA – Loss Reducing Agent
of
Electrons Electrons
Or RED CAT , AN OX
Reduction Oxidation
Cell notation is as easy as ABC (anode, bridge, cathode) /*marami pong kulang kasi po di ko na kinaya*/
© jgnoche 2015
