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Analytical Chemistry > Lecture - Midterm > Flashcards

Lecture - Midterm Flashcards

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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
State of rest or balance
Equilibrium
27
Reaction rates of forward and reverse reactions are generally not zero but-
Equal
29
Biological catalysts
Enzymes
30
Catalysts are ____________ in the course of the reaction
Not consumed
31
A _____ increase in temperature will double the reaction rate
10 degrees Celsius
32
* 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
Pressure and density
34
Equilibria that happen in phase transitions
Phase equilibria
35
Concerning the composition of a reaction mixture at equilibrium
Equilibrium aspect
35
Example of pressure and density
Density tower
36
* 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
Heat
37
For systems that are not equilibrium yet, the ratio calculated from the mass action law is called:
Reaction quotient or Q
39
The Q values of a closed system have a tendency to reach a limiting value called:
Equilibrium constant or K
39
A system has a tendency to reach an:
Equilibrium state
40
Isolated portion of the universe
System
41
Both reactants/products are present in concentrations which have no further tendency to change with time.
Chemical equilibrium
41
Anything outside the system
Environment
42
System is isolated from its environment that there is no energy or mass transferred into or out of the system
Closed system
43
Opposite of recombination
Dissocation
45
In measuring temperature, the thermometer must be at _________ as the system it measures
The same state
46
[true or false] Equilibrium states are reached for physical as well as chemical reactions
True
47
We read temperature of the thermometer when-
Heat transfer between the thermometer and the system stops
48
Equilibrium is dynamic in the sense that changes continue, but the net change is
Zero
49
Factors affecting equilibrium accdg to Le chatelier's law
* change in temperature * change in pressure * change in concentration
50
Strong acids
* HCl * HNO3 * H2SO4 * HBr * HI * HClO3 * HClO4
51
Problem: | A weak acid has a pKa of 4.994 and the solution pH is 4.523. What percentage of the acid is dissociated?
``` 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
If forward reaction is endothermic, an increase in temperature causes the system to shift in:
Forward direction
53
If forward reaction is exothermic, increase in temperature causes the system to shift in the:
Reverse direction
53
[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
True
54
Increase in pressure causes the system to shift in the direction of:
Fewer gas molecules
55
Decrease in pressure causes the system to shift in the direction of:
More gas molecules
56
The more viscous, the ______ the reaction rate
Slower
58
Factors related to chemical reactions that do not affect the position of equilibrium
* catalyst | * inert gases
58
* speeds up reverse reaction as well * net result is that changes in its concentration will not affect the equilibrium concentration of reactants and products
Catalyst
60
Solute that completely or almost completely ionizes or dissociates in a solution
Strong electrolyte
61
Strong electrolyte ---->
Cation + + Anion -
62
[true or false] | For strong electrolytes, a single reaction arrow shows that the reaction occurs completely in one direction
True
63
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
Dissocation
64
If the number of particles on each side of the reactions is equal, then a change in pressure:
Has no effect
64
Weak acids
* CH3COOH * HCOOH * HF * HCN * HNO2 * HSO4
65
Formula for %dissociation
%dissociation = H/HA x 100
66
Strong bases
* NaOH * KOH * Ba(OH)2
67
A-
Conjugate base
68
Weak Bases
* NH3 * CH3NH2 * C5H5N * NH4OH
69
A quantitative measure of the strength of an acid in solution.
Acid Dissociation Constant or Ka Or acidity constant Or acid-ionization constant
70
[true or false] | The larger the Ka value, the more dissociations of the molecules in solutions and thus the stronger the acid
True
72
The equilibrium of an acid dissociation can be written symbolically as:
HA A- + H+
73
Generic acid
HA
74
H+
Hydrogen ion or proton
75
In the case of aqueous solutions, exists as the hydronium ion or solvated proton
H+
76
Unit of HA
Mol/li
77
Mathematical model that explains and predicts behaviors of solutions in dynamic equilibrium
Law of Mass Action
77
In a closed system, changes continue, but eventually there is ______ over time
No net change
77
[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
True
77
Formula for conjugate base or H+ ion:
H+ = 10^-pH
78
Water vapor in the space above water eventually reaches ______
Equilibrium vapor pressure
79
What do you take off when you separate acids?
Hydrogen ions

Analytical Chemistry (3 decks)

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