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Analytical Chemistry > Lecture - Midterm > Flashcards

Lecture - Midterm Flashcards

0
Q

Measure of change of concentration of reactants/ change in concentration of products per unit time

A

Reaction rate

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1
Q

Formula for pKa

A

pKa= -log10^Ka

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3
Q

Example of phase and surface area

A

Internal combustion and heat

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4
Q

Factors affecting the speed of reaction

A
  • Concentration of the reactant
  • Temperature effects
  • Phase and surface area
  • Solvent Viscosity
  • Presence of a Catalyst
  • Pressure and Density
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5
Q

Change of a substance into a new one that has a different chemical identity

A

Chemical reaction

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6
Q

Two aspects of mass action law

A
  • equilibrium aspect

* kinetic aspect

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7
Q

Concerning the rate equation for elementary reactions

A

Kinetic aspect

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8
Q

Ka is usually written as:

A

Ka= [A-] [H+]/ [HA]

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9
Q

Increasing the concentration of one or more reactants allows the reaction to go-

A

Quicker

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10
Q

The more molecules, the more ______ between molecules, the ______ rate of reaction

A
  • collisions

* faster

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11
Q

Example of solvent viscosity

A

Water and honey

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12
Q

Example of presence of a catalyst

A

Alcohol dehydrogenase facilitates the interconversion between alcohol and aldehydes or ketones with reduction of NAD +

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13
Q

Increasing temperature of a system increases the _______________ of its constituent particles

A

Average kinetic energy

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14
Q
  • increasing temperature of a system increases the average kinetic energy of its constituent particles
  • as the average kinetic energy increases, the particles move faster and collide more frequently per unit time and posses greater energy when they collide
  • both of these factors increase the reaction rate
  • a 10 degree Celsius increase in temeperature will double the reaction rate
A

Temperature effects

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15
Q

When 2 reactants are in the same fluid phase, their particles collide more frequently than when one or both reactants are solids (or when they are in different that do not mix)

A

Phase and surface area

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17
Q

A covered cup of coffee will not be colder than or warmer than the room temperature after it had been in there for a few hours

A

Equilibrium pertaining to flow of energy

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18
Q

Increase in concentration of one or more reactants, or decrease in concentration of one or more products causes the system to shift in the:

A

Forward direction

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19
Q

Forward reaction proceeds at the same rate as the reverse reaction

A

Chemical equilibrium

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19
Q
  • increasing the concentration of one or more reactants allows the reaction to go quicker
  • the more molecules, the more collisions between molecules,the faster rate of reaction
A

Concentration of the reactant

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20
Q
  • in highly viscous solvents, dissolved particles diffuse much more slowly than in less viscous solvents and can collide less frequently per unit time
  • thus, the reaction rates of most reactions decrease rapidly
  • the more viscous, the slower the reaction rate
A

Solvent viscosity

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21
Q

Speeds up the rate of reaction by lowering the activation energy barrier

A

Catalyst

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22
Q

A catalyst speeds up the rate of reaction by lowering the ________

A

Activation energy barrier

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23
Q

Addition of an inert gas to a system at equilibrium will cause an __________ within the reactor

A

Increase in total pressure

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24
Q

Problem: a 0.120 M solution of a generic weak acid (HA) has a pH of 3.26. Determine the Ka.

A 
Sol: HA  H+  +   A-
       Ka = [H] [A]/ [HA]
       [H+]=10^-pH
              = 10^ -3.26
              = 5.4954 x10^-4 M
       A=H
       [A-]=5.4954x10^-4 M
    Ka=[(5.4954x10^-4) (5.4954x10^-4)/ 0.120
    Ka= 2.52x10^-6
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25
Q

State of rest or balance

A

Equilibrium

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27
Q

Reaction rates of forward and reverse reactions are generally not zero but-

A

Equal

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29
Q

Biological catalysts

A

Enzymes

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30
Q

Catalysts are ____________ in the course of the reaction

A

Not consumed

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31
Q

A _____ increase in temperature will double the reaction rate

A

10 degrees Celsius

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32
Q
  • when you increase the pressure, the molecules have less space in which they can move
  • the greater the density of molecules increases the number of collisions
  • when you decrease the pressure, molecules don’t hit each other as often and the rate of reaction decreases
A

Pressure and density

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34
Q

Equilibria that happen in phase transitions

A

Phase equilibria

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35
Q

Concerning the composition of a reaction mixture at equilibrium

A

Equilibrium aspect

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35
Q

Example of pressure and density

A

Density tower

36
Q
  • Energy flowing from a high temperature object to a low temperature object
  • when the two objects are at the same temperature, there is no net flow of energy or heat
37
Q

For systems that are not equilibrium yet, the ratio calculated from the mass action law is called:

A

Reaction quotient or Q

39
Q

The Q values of a closed system have a tendency to reach a limiting value called:

A

Equilibrium constant or K

39
Q

A system has a tendency to reach an:

A

Equilibrium state

40
Q

Isolated portion of the universe

41
Q

Both reactants/products are present in concentrations which have no further tendency to change with time.

A

Chemical equilibrium

41
Q

Anything outside the system

A

Environment

42
Q

System is isolated from its environment that there is no energy or mass transferred into or out of the system

A

Closed system

43
Q

Opposite of recombination

A

Dissocation

45
Q

In measuring temperature, the thermometer must be at _________ as the system it measures

A

The same state

46
Q

[true or false] Equilibrium states are reached for physical as well as chemical reactions

47
Q

We read temperature of the thermometer when-

A

Heat transfer between the thermometer and the system stops

48
Q

Equilibrium is dynamic in the sense that changes continue, but the net change is

49
Q

Factors affecting equilibrium accdg to Le chatelier’s law

A
  • change in temperature
  • change in pressure
  • change in concentration
50
Q

Strong acids

A
  • HCl
  • HNO3
  • H2SO4
  • HBr
  • HI
  • HClO3
  • HClO4
51
Q

Problem:

A weak acid has a pKa of 4.994 and the solution pH is 4.523. What percentage of the acid is dissociated?

A 
Sol: Ka=10^-pKa
           = 10^-4.994
           = 1.0139 x 10^-5
       HA  H + A
       Ka=[H] [A] / HA
       [H+] = 10^-pH
               =10^-4.523
               = 3.00x10^-5 M
       [A-]=3.00x10^-5 M
        1.0139x10^-5=(3.00x10^-5)^2\x
        X= 8.88x10^-5 M
    %dissociation=H/HAx100
                           = 3.00x10^-5/8.88x10^-5 x 100 = 33.8%
52
Q

If forward reaction is endothermic, an increase in temperature causes the system to shift in:

A

Forward direction

53
Q

If forward reaction is exothermic, increase in temperature causes the system to shift in the:

A

Reverse direction

53
Q

[true or false] in adding an inert gas, none of the partial pressures of reactants or products are changed, and so the equilibrium is not upset, and no shifting is needed to bring the system back to equilibrium

54
Q

Increase in pressure causes the system to shift in the direction of:

A

Fewer gas molecules

55
Q

Decrease in pressure causes the system to shift in the direction of:

A

More gas molecules

56
Q

The more viscous, the ______ the reaction rate

58
Q

Factors related to chemical reactions that do not affect the position of equilibrium

A
  • catalyst

* inert gases

58
Q
  • speeds up reverse reaction as well
  • net result is that changes in its concentration will not affect the equilibrium concentration of reactants and products
60
Q

Solute that completely or almost completely ionizes or dissociates in a solution

A

Strong electrolyte

61
Q

Strong electrolyte —->

A

Cation + + Anion -

62
Q

[true or false]

For strong electrolytes, a single reaction arrow shows that the reaction occurs completely in one direction

63
Q

Process in which molecules (or ionic compounds such as salts or complexes) separate or split into smaller particles such as atoms, ions or radicals usually in reversible manner

A

Dissocation

64
Q

If the number of particles on each side of the reactions is equal, then a change in pressure:

A

Has no effect

64
Q

Weak acids

A
  • CH3COOH
  • HCOOH
  • HF
  • HCN
  • HNO2
  • HSO4
65
Q

Formula for %dissociation

A

%dissociation = H/HA x 100

66
Q

Strong bases

A
  • NaOH
  • KOH
  • Ba(OH)2
67
Q

A-

A

Conjugate base

68
Q

Weak Bases

A
  • NH3
  • CH3NH2
  • C5H5N
  • NH4OH
69
Q

A quantitative measure of the strength of an acid in solution.

A

Acid Dissociation Constant or Ka
Or acidity constant
Or acid-ionization constant

70
Q

[true or false]

The larger the Ka value, the more dissociations of the molecules in solutions and thus the stronger the acid

72
Q

The equilibrium of an acid dissociation can be written symbolically as:

A

HA A- + H+

73
Q

Generic acid

74
Q

H+

A

Hydrogen ion or proton

75
Q

In the case of aqueous solutions, exists as the hydronium ion or solvated proton

76
Q

Unit of HA

77
Q

Mathematical model that explains and predicts behaviors of solutions in dynamic equilibrium

A

Law of Mass Action

77
Q

In a closed system, changes continue, but eventually there is ______ over time

A

No net change

77
Q

[true or false]

The larger the value of pKa, the smaller the extent of dissociation at any given pH that is, the weaker the acid

77
Q

Formula for conjugate base or H+ ion:

A

H+ = 10^-pH

78
Q

Water vapor in the space above water eventually reaches ______

A

Equilibrium vapor pressure

79
Q

What do you take off when you separate acids?

A

Hydrogen ions

Analytical Chemistry (3 decks)

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