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Chem 105 Fall '14 > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

Solution

A

homogeneous mixture (uniform) of two or more substances

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2
Q

Solute

A

component of a solution that is present in lesser quality than the solvent

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3
Q

solvent

A

solution component presented in the largest quality

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4
Q

aqueous solution

A

when the solvent is water

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5
Q

electrolytes

A

formed from solutes that are soluble ionic compounds that disassociate in solution to produce ions that behave as charge carriers; they conduct energy

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6
Q

true solution

A

homogeneous mixture with uniform properties throughout

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7
Q

pure substance

A

has only one component (ie water)

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8
Q

true substance

A

has more than one substance; and is homogeneous throughout solution (particles are not large enough to scatter light)

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9
Q

colloidal susbention

A

has solute particles distributed throughout a solvent; but it is not completely homogeneous **larger particles, not identical, particles participate.

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10
Q

whats the difference between a solution particle and precipitant?

A

1nm = solution particles

particles larger than 200nm are precipitates

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11
Q

suspension

A

heterogenous mixture that contains particles much later than colloid suspension (overtime particles settle at bottom and form second phase)

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12
Q

solubility

A

how much solute can dissolve in a given volume of solvent

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13
Q

what affects the solubility?

A
  • polarity of solute & solvent-like goes with like (more similar the more they dissolve & greater distance, the less soluble the solute)
  • temperature- increased temp increased solubility (usually)
  • pressure (little affect on solids & liquids)
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14
Q

saturated solute

A

when a solution contains all the solute that can be dissolved at a particular temperature **increased temp, you can dissolve more- decreased temp it will dissolve less

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15
Q

supersaturated solute

A

as solute is cooling, the excess solute may remain in a solution only for a portion of time before the excess will fall to the bottom… It is unstable

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16
Q

What is a dynamic equilibrium?

A

When an excess solute is added to solvent, it begins to dissolve & contains until it establishes a “dynamic equilibrium btwn dissolved and undissolved.

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17
Q

What is Henry’s Law?

equation?

A

the number of moles of a gas dissolve in a liquid at a given temp to proportionally to the pressure of gas…
-solubility is directly proportional to pressure of gas in atmosphere… temp must stay the same
Equation:
M=kp (at fixed temp)

**solubility increases at lower temp, decreases at higher temp.

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18
Q

concentration:

A

the amount of solute dissolved in a given amount of solution. Has a profound effect on properties of solution.

  • Physical- melting point & boiling point
  • Chemical- solution reactivity
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19
Q

How do you calculate the mass to volume percent of a concentration?

A

concentration= m (amount of solute in g)/ v (amount of solution in mL) X 100 —which will give the percent of concentration

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20
Q

How do you calculate the mass to mass percent of a concentration?

A

percent of mass/mass = (g solute)/(g of solution) X 100

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21
Q

How do you calculate the parts per thoustand (ppt) and parts per million of a concentration %?

A

PPT= g solute/g solution X 10 to the third

PPM= g solute/ g solution X 10 to the sixth

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22
Q

Molarity

A

M = moles of solute/L solution

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23
Q

What is the equation for a dilution?

A

M1V1=M2V2

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24
Q

what are the 4 colligative properties?

A

1: Vapor Pressure Lowering
2: Freezing point Depression
3: Boiling point elevation
4: osmotic pressure

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25
Q

calculating molality?

A

molality= mol solute/kg solvent

26
Q

diffusion

A

net movement of solute or solvent molecules from an area of high concentration to an area of low concentration

27
Q

concentration gradient

A

the area where the concentration decreases over distance

28
Q

selective permeable membrane

A

a membrane that only allows small molecules to pass through freely, larger molecules & highly charged ions are restricted to cross

29
Q

semipermeable membranes

A

a membrane that allows a solvent but not the solute to diffuse from one side to the otehr

30
Q

osmosis

A

is the diffusion of a solvent (water) through a semipermeable membrane in response to a water concentration gradient.

31
Q

osmotic pressure

A

the pressure that must be exerted to stop the flow of water across a semipermeable membrane by osmosis

32
Q

osmolarity

A

the molaritry of particles in solution

33
Q

hypotonic solution

A

a solution that has a lower osmolarity

34
Q

hypertonic solution

A

a solution with a greater osmolarity

35
Q

what is the calculation for an equivalent?

A 
eq/l = (eq/mol ion) (mol ion/L)
then goes to....
M= (mol ion/L)
then to...
eq/L = (eq/ mol ion)M
36
Q

what are the three basic laws about thermodynamics?

A

1: Energy cannot be created nor destroyed (only converted from one form to another)
2: the universe spontaneously tends towards increasing disorder or randomness
3: The disorder of a pure, perfect crystal @ absolute zero (O Kelvin) is zero

37
Q

heat flow

A

transfer of the thermal energy to the surroundings

38
Q

system

A

only contains the process that is under study

39
Q

surroundings

A

encomposed as the rest of the universe (energy can either be lost from the system to the surroundings or energy can be gained by the system from the surroundings.)

40
Q

The first law of thermodynamics?

A

energy of the universe is constant (cannot be created nor destroyed)

41
Q

exothermic

A

energy leaves the system during chemical reactions (gives off heat)

42
Q

endothermic

A

energy enters system during chemical reactions (takes in heat, to break bonds)

43
Q

enthalpy

A

term used to represent heat (delta H)

  • delta H + = if energy is absorbed in a reaction (endothermic)
  • delta H - =energy is released in reaction, exothermic
44
Q

entrophy

A

measure of the randomness of a chemical system (delta S)

  • delta S + = exothermic & spontaneous
  • delta S - = endothermic & nonspontaneous
45
Q

which one has greater entrophy?
He (s) or Na (s)

H2O(l) or H2(g)

A

Na

H2O liquid

46
Q

what is the 2nd law of thermodynamics?

A

everything in the universe is spontaneous & tends toward increasing disorder or randomness (entropy)

47
Q

free energy

equation?

A

delta G; represents the combined contribution of the enthalpy and entropy values for a chemical

formula: delta G = (delta H) - (T) X (delta s)

  • delta G + = always spontaneous
  • delta G - = never spontanous
48
Q

calorimetry

A

the measurement of heat energy changes in a reaction

49
Q

calorimeter

A

device that measure heat changes in calories

50
Q

specific heat

equation?

A

SH of a substance is defined as the number of Calories of heat needed to raise the temp of 1g of substance 1 deg of C.

We need to know SH; mass of solute, temperature change
Q= (m) X (delta T-change in temp) x (SH)

51
Q

what is the SH of water?

A

I Cal/g degree of C

52
Q

activation energy

A

the minimum amount of energy required to initiate a chemical reaction

53
Q

activated complex

A

an extremely unstable, short lived intermediate complex

54
Q

what factors affect reaction rates?

A

1: structure of reacting species (opposite charges react faster, same charges have no reaction & if it is already dissociated than it has a low activation energy)
2: molecular shape & orientation
3: concentration of reactant (increased concentration, increased rate)
4: temperature of reactants (temp increase = rate increase)
5: physical state of reactants (how far apart the particles are/how often them collide ( liquids>gas>solid)
6: presents of a catalyst (increases reaction rate)

55
Q

higher kinetic energy rate order:

A

liquids>gas>solid

56
Q

equilibrium reactions

A

chemical reactions that do not go to completion; represented by reactants only:
rate= k(r) –depending on if it is first order or second order the (r) will be to that power

**once it reaches an equilibrium then it will be balanced.

57
Q

reversible reaction

equation?

A

a process that can occur both ways

keq = products/reactions

**comes from a balanced equation; the product or reactant can be to a specific power depending on how many ions of that particular

58
Q

dynamic equilibrium

A

when the rate of the forward process in a reversible rate is exactly balanced by the rate of the reverse process.

ie: N2 + 3H2 = 2NH3
rate r= kr [N2] [H2] to the third power
rate f= kf [NH3) to the second power

(product over reactant)

59
Q

what happens when you have a

larger k constant?
smaller k constant?

A

larger - more products

smaller- more things stay in reactant form

60
Q

what is LeChaletier’s principle?

A

if a stress is placed on a system that is at equilibrium, the system will despond by altering the equilibrium composed in such a way to minimize stress.
ie:
product introduced - shift to the right
reactant introduced - shift to the left

Chem 105 Fall '14 (4 decks)

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