Chem1605: Chap 7 8 5 6
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~~~~~ Chapter 7 ~~~~~~~
Reaction rates and Chemical Equilibrium
which is the study of the rates of a chemical reaction?
What's an effective collision?
a collision that results in a reaction.
For a reaction to take place between A and B, what needs to happen first?
- - One or more covalent bonds need to broken in A or B or both. This requires energy
- - Energy comes form the collision of A and B.
- - if the energy is large enough, bond will break and a reaction will happen, if the energy is too low, the molecules will bounce apart without reacting.
What is activation energy?
minimum energy necessary for a reaction to occur.
What does the energy of any collision depend on?
the speed. *head on collision offer more impact*
Even if two molecules collide with an energy greater than the activation energy, what else needs to happen for a reaction to occur?
the proper orientation of the molecules.
How is the frequency of collisions an important factor?
If more collisions take place, the chances that more of them will have sufficient energy and reaction will take place.
Why are reactions between ions in aqueous solution generally much faster than reactions between covalent molecules?
- -reactions involving aqueous solutions do not require bond breaking and have low activation energy.
- - reactions between covalent bonds require the breaking of the covalent bond and have higher activation energy.
What makes a reaction exothermic?
the amount of energy released in creating a new bond is greater than that required to break the original bonds.
Energy must be put into the system in order to get any back.
the ___ the activation energy, the ____ reaction; the ____ the activation energy, the ____ the reaction.
What is the tradition state and what happens when the reacting molecules reach this point?
- the "top of the hill".
- One or more original bonds are partially broken and one or more new bonds may be in the process of formation.
What happens to many reactions when the temperature goes up by 10*C?
the rate of reaction doubles.
what's a catalyst?
any substance that increases the rate of the reaction without itself being used up.
how do catalysts work? what happens without the catalyst?
allowing the reaction to take a different pathway, one with a lower activation energy. Catalysts provide a lower hill and with a lower activation rate, the reaction rate is faster.
Without a catalyst, the reactants would have to jump over a "higher hill" which means slower reaction time.
What is a general rule when writing an equilibrium expression?
pure solids, and pure liquids are not included earn writing an equilibrium expression.
Only concentrations of gases and solutes in solution are included.
How to know the position of the equilibrium?
- -Find out whether the number is larger or smaller than one.
- - If # > 1 ; equilibrium lies to the right
- - If # < 1 ; equilibrium lies to the left.
base: substance that produces OH- ions in aqueous solutions
For the reaction A + B ® 2 C, what is true?
B is consumed at the same rate that A is consumed
What can change the numerical value of the equilibrium constant of a particular reaction?
increasing the temperature
~~~~ Chapter 8 ~~~~~
Acids and Bases
According to Arrgenius, What's the definition of an acid and a base? How else can they be written?
Acid: substance that produces H3O+ ions in aqueous solutions. Can be written as Ka
Base: substance that produces OH- ions in aqueous solutions. Can be written as Kb
What happens when an acid dissolves in water?
-- What happens to HCl dissolves in water?
it'll react with the water to produce H3O+.
HCl(aq) + H2O (aq) -> H3O+ (aq) + Cl- (aq)
what happens when a base dissolves in water?
-- What happens to ammonium dissolved in water?
it'll produce OH- ions.
NH3(aq) + H2O (aq) -><- NH4+ + OH-
What is Arrhenius' definition of a strong acid?
one that reacts completely or almost completely with water to form H3O+ ions.
there are ___ common strong bases. which are all ______
six; metal hydroxides.
Know the 6 strong acids and bases!
~ pg. 241 ~
What causes these strong bases to be "strong bases" ?
When they dissolve in water they ionize completely to give OH- ions.
Is the strength of an acid or a base related to its concentration?
According to Thomas Lowry, what is the definition of an acid and a base?
Also, what's an acid-base reaction?
Acid: proton donor
Base: Proton aceptor
Acid-Base reaction: a proton-transfer reaction.
What's a conjugate acid-base pair?
when an acid transfers a proton to a base, the acid is converted to its conjugate base.
When a base accepts a proton, it is converted to its conjugate acid.
There are four steps to determine the position of an acid-base equilibrium.
What are they?
- 1. Identify the two acids in the equilibrium; one is on the left side of the equilibrium, and the other is on the right side.
- 2. Determine which acid is the stronger acid and which acid is the weaker acid.
- 3. Do step 2, but with the base now. Remember: the stronger acid gives the weaker conjugate base and the weaker acid gives the stronger conjugate base.
- 4. The stronger acid and stronger base react to give the weaker acid and weaker base. The position of equilibrium lies on the side of the weaker acid and weaker base.
if you are given the Ka for benzoic acid, how do you find the pKa?
pKa = - log pK
How do you determine the strength by comparing the Ka values and the pKa values.
If using the Ka values, the stronger acid has the larger Ka.
If using the pKa value, the stronger acid has the lower pKa
when strong acids react with active metals, what do they produce? What type of reaction is this?
- hydrogen gas and a salt.
- Redox reaction
What is produced when acids and metal hydroxides react with each other?
gives off salt and water
What happens when strong acids and metal oxides react with each other?
water and soluble salt is produced.
what is Kw called and what is its value?
- concentration of water.
- 1.0 x 10^-14
Kw = [H3+O][OH-]
what is the pH level of blood?
between 7.35 - 7.45
what's another way to write pH and pOH?
pH = pKA
pOH = pKB
There are 7 equations you need to know.
~write it down~
~~~~~~~ Chapter 5/6 ~~~~~~~~~~
Gases, Liquids and Solids / Solutions and Colloids
Where does the three states of matter fall onto when considering temperature?
high temp > med temp > low temp
gas > liquid > solid
what is the same between all three states? What's different?
- the attractive forces between the molecules.
- Kinetict energy
what is pressure commonly measured in?
millimeters of mercury. (mm Hg)
How many mm Hg is 1 atm (atmosphere)
760 mm Hg
What's Boyle's Law. What's the equation?
if pressure doubles, the volume decreases by one-half.
P1V1 = P2V2
What's Charle's Law? what's the equation?
as long as the pressure on a gas remains constant, increasing the temperature of the gas causes an increase in the volume occupied by the gas.
V1/T1 = V2/T2
What's Gay-Lussac's Law? What's the equation?
as the temperature of the gas increases, the pressure increases proportionately.
P1/T1 = P2/T2
What's the combined gas law equation?
P1V1/T1 = P2V2/T2
What's Avogadro's law? When is it valid?
- if the temperature, pressure and volumes of two gases are the same, then the two gases contain the same number of molecules, regardless of their identity.
- Valid for all gases.
What is the standard pressure and temperature which chemists have chosen?
1 atm for pressure and 0*C (273K) as standard temperature.
What's the ideal gas law equation?
PV = nRT
- where P = pressure of the gas in (atm)
- V = volume of the gas in Liters
- n = amount of gas in moles
- T = temperature in Kelvins
- R = constant for all gases called ideal gas constant.
How much atm is in a pressure (P) of a gas?How much liters (L) is in a volume (v) of gas?How much moles (mol) is in a gas (n)?
What's the temperature (T) in Kelvins (K) is the gas?
- P = 1.00 atm
- V = 22.4 L
- n = 1.00 mol
- T = 273 K
How do you find R?
- one mole of any gas at STP occupies a volume of 22.4 L.
R = 0.0821
- R = PV/nT
- = (1.00 atm)(22.4L)/(1.00mol)(273K)
- = 0.0821
What's Dalton's law of partial pressure?
PT = P1 + P2 + P3 + ....
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