Exam 2 Flashcards
Lectures 17-26
Osmosis
selective passage of solvent molecules through a porous membrane from a more dilute solution to a more concentration one
* solvent flows from more dilute solution to a more concentrated one
Osmotic pressure
pressure required to stop osmosis
Hypotonic solution
has a lower concentration of particles than the cell
What happens if a cell is placed in a hypotonic solution
water (solvent) rushes into cell, cell swells, and bursts
Hypertonic solution
has a higher concentration of particles than the cell
What happens if a cell is placed in a hypertonic solution
water moves out of the cell, causing it to shrink
Balancing equations (4 points)
- if only C, H, O in equation, balance it in that order
- balance a free element at the end
- balance a metal before a nonmetal
- don’t seperate polyatomic ions
Combustion
reactant: oxygen
product: CO2 and H2O
rate
how much a quantity changes in a given time
thermodynamics
whether free energy was released or absorbed
collision theory
collision frequency
collision energy
collision orientation
What are the 4 factors that affect rate?
- concentration of reaction
* direct - temperature
* direct - physical state
* 2 liquids = more collisions
* 1 solid 1 liquid = less - catalyst
* not consumed
* only small amount needed
orient molecules so correct orientation is greater
For each __ rise in temp, the rate of reaction __
10 degrees celcius
doubles
rate expression
gives relationship between the different rates of change of reactants and products of the same reaction
* reactions are negative
* products are positive
differential rate law
relationship between rxn rate and reacatant concentration
Which factor affects k?
temperature
Which factor does not change k?
concentration
How do you find order of the reaction?
add the exponents of the reactants
Sign for rate of appearance and disappearance
appearance=+
disappearance=-
Half-life
time it takes for half the substance to disappear
relationship between order for half life and concentration
0 - direct
1st - no relationship
2nd - inverse
zero order half life gets longer or shorter, why
half life gets shorter with time
rate is constant, so it takes shorter time to make substance disappear
For first order half life, which factors depend on concentration and which ones don’t
depend on concentration: rate *rate=k[A]
does not depend on concentration: k and half-life
Second order half-life gets longer or shorter, why
half-life is getting longer with time because it is dependent on collision, and lower concentration means less collusions
activation energy
minimum amount of energy to START a reaction * lowest activation energy is most stable and fastest
transition state
when molecules collide effectivelt, they form an activated complex
* partially broken and partially formed bonds
* unstable
* transitional species: partly between reactant and product
How do you find the overall order of the reaction?
add the exponents of the reactants
remember
- check if the equation is balanced
- don’t forget k in rate
- for elementary reactions (NOT overall reaction), the order can be determined from the coefficients
- if it says “second decay”, you have to do it twice
- include units for k
- some equations line up with y=mx+b
- make R into kJ if needed