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MASS ACTION EXPRESSIONS

products ÷ Reactants = [A]s[B]v ÷ [C]u[D]t
s, v, u, t are in expontential form
ONLY INCLUDE GASES AND AQUEOUS COMPOUNDS IN A Keq EQUATION
If K = 1 the concentration of products and reactants are equal
If K > 1 the concentration of products is less than the the concentration of the reactants
If K < 1 the concentration of products is greater than the concentration of the reactions
ex: 2NO2 <=> N2O4
At equilibrium, the concentration of NO2 is 0.2M and the concentration of N2O4 is .8M. Find the Keq and tell if the reaction or product is favored K = [0.8M] ÷ [.2M] = 20M; more reactants

Le CHATLIERS PRINCIPLE: If a system at equilibrium is 'stressed' the system will respond in such a way to minimize the stress
ex: N2 + 3H2 <=> 2NH3 Add H2 equilibrium shifts to the right
If the pressure is higher, the reaction shifts to the side with the fewer moles of gas. If the pressure is lower, the reaction will shift to the side with the larger number of moles.

Changing the Pressue of a reaction
When the pressure increases, the reaction shifts to the side with fewer moles of gas
When the pressure decreases, the reaction shifts to the side with greater moles of gas

Ex: CH3OH <=> 2H2 + CO2

if you add C3OH, the reaction will shift to the right
PRACTICE:
1. What will happen if you add CO?
2. What will happen if you remove H2?


Solubility Product Equilibria (Ksp)

solubility product constant- the product of the molar concentrations of its ions in a satured solution, each raised to the power that is the coefficient of that ion in the balanced chemical equation

Ex: NaCl(s) <=> Na(aq) + Cl-(aq)
Ksp= [Na+] [Cl]
What happens if KCl is added?
K+(aq) + Cl-(aq), there is a common ion between Cl-(aq)


Acids and Bases

  • Acids- anything that can donate a proton
  • Bases- anything that accepts a proton
Ex: HCl + H20 => H3O + Cl
HCl is the acid because it lost a proton, and H2O is the base because it gained a proton
After losing a proton, the acid species becomes the conjugate base and after gaining a proton, the base species becomes the conjugate acid.

PRACTICE:
1. NH3 + H20 => NH4+ + OH-
What is the acid and what is the base?
2. CH3COOH + NH2- => NH3 + CH3COO-
What is the acid and what is the base?
What is the conjugate acid and the conjugate base?

Predicting Acidity
H-Cl
Hydrogen is "loose" because it is 2.1 compared to Cl's 3.0, making it a stronger acid

Acid Strength
2 Scales: 1. Ka/Pka
2. pH
If Ka is large, the acid is stronger
If Ka is smaller, the acid is weaker

pKa= - log Ka
THE LARGER THE Ka VALUE= WEAKER
THE SMALLER THE Ka VALUE= STRONGER

PRACTICE:
1. Find the pka of an acid whose ka is 1.8 x 10E-5
2. Find the pka of an acid whose ka is 2.9 x 10E-15

PH= - log
Ex: For H20, pH= - log (1 x 10E-7) = 7

PH SCALE

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Nuetralizing Acids (or bases)
- an acid is nuetralized when the color disapears
- to figure out the strength of an acid use the equation M1 V1 = M2 V2




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1. Homeostasis: your bodie's equilibrium
2. Amphoteric: capable of acting as an acid or a base
3. Vinegar is an acetic acid
4. Acidus refers to sour and bases refers to bitter
5. H30+ makes the acid stronger
6. Titration- measuring amount of base needed to go into nuetralize


ANSWERS (in order)
1. shift to the left
2. shift to the right

1. NH3 is the base and H20 is the acid
2. CH3COOH is the acid, NH3 is the conjugate acid
NH2 is the base, CH3COO is the conjugate base

1. pka = 4.74
2. pka = 14. 5