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General Chemistry Flashcards

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MCAT flashcards
1
Q

What does paramagnetic mean?

A

the atom has unpaired electrons

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2
Q

What does diamagnetic mean?

A

the atom has only paired electrons

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3
Q

Where do the electrons get removed from when forming a cation?

A

the subshell with the highest n value

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4
Q

What is the maximum number of electrons allowed in a single atomic energy level in terms of the principal quantum number n?

A

2n^2

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5
Q

What is the maximum number of electrons that can fill a subshell?

A

4l + 2 (l=quantum number l)

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6
Q

What does mass number (superscript) refer too?

A

the number of protons and neutrons in an atom/isotope

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7
Q

What are representative elements?

What are nonrepresentative elements?

A

representative: elements with their valence electrons in either orbitals s or p
nonrepresentative: transition elements, elements with their valence electrons in orbitals s and d or s and f

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8
Q

How do anions and cations affect ionic radius?

A

the ionic radii of anions are larger

the ionic radii of cations are smaller

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9
Q

What three elements are the exceptions to the electronegativity trend and have negligible electronegativity?

A

The first three noble gases: He, Ne, Ar

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10
Q

Which is larger, first or second ionization energy?

A

second ionization energy is always larger than first ionization energy because removing an additional electron requires one to overcome a significantly larger electrostatic force

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11
Q

What property explains why metals are used for making wires that conduct electricity?

A

metals have valence electrons that can move freely

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12
Q

What type of ions do alkali earth metals form?

A

divalent cations (+2)

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13
Q

What is the order of increasing energy for subshells?

A

s<p></p>

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14
Q

What periodic trend determines whether a covalent bond is polar or nonpolar?

A

The polarity in a covalent bond is determined by differences in electronegativity between the two atoms involved.

nonpolar: the electron pair is shared equally
polar: the electron pair is shared unequally

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15
Q

What is the equation for formal charge?

A

formal charge = #valence electrons - #dots - #lines

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16
Q

What is bond strength?

A

bond strength is defined by the electrostatic attraction between nuclei and electrons; multiple bonds (higher bond order) increases strength

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17
Q

What is bond length?

A

bond length is a consequence of bond strength. The stronger the bond, the shorter it is

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18
Q

What is bond energy?

A

bond energy is the minimum amount of energy needed to break a bond. The stronger the bond, the higher the bond energy.

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19
Q

For what values of ∆EN will a nonpolar covalent bond form?

A

0 to 0.5

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20
Q

For what values of ∆EN will a polar covalent bond form?

A

0.5 to 1.7

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21
Q

For what values of ∆EN will an ionic bond form?

A

1.7 or higher

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22
Q

What number of regions of electron densities apply to which geometric shapes?

A

2: linear
3: trigonal planar
4: tetrahedral
5: trigonal bipyramidal
6: octahedral

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23
Q

What is a coordinate covalent bond?

A

a two electron covalent bond where both electrons come from the same atom

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24
Q

What is the equation for gram equivalent weight?

A

gram equivalent weight = molar mass/n

n = the number of particles of interest produced or consumed per molecule of the compound in the reaction

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25
Q

What is the equation to determine how many equivalents in a compound are present?

A

equivalents = mass of compound (g)/gram equivalent weight (g)

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26
Q

What is the equation for normality?

A 
N = M x equivalents/mole
M = molarity
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27
Q

What is the difference between empirical and molecular formulas?

A

empirical formula gives the simplest whole-number ratio of the elements in the compound (CH).
molecular formula gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula (C6H6).

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28
Q

How do you calculate percent composition?

A

percent composition = mass of element in formula/molar mass x 100%

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29
Q

How to recognize a combination reaction?

A

A + B –> C

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30
Q

How to recognize a decomposition reaction?

A

A –> B + C

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31
Q

How to recognize a combustion reaction?

A

it will always produce carbon dioxide and water, and usually involves O2 and a hydrocarbon in its reactants

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32
Q

What is a neutralization reaction?

A

neutralization reactions are a specific type of double-displacement reaction in which an acid reacts with a base to produce a salt, and usually water.

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33
Q

What is the percent yield equation?

A

percent yield = actual yield/theoretical yield x 100%

theoretical yield = the amount of product predicted

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34
Q

ammonium

A

NH4+ (+1)

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35
Q

acetate

A

C2H3O2- (-1)

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36
Q

cyanide

A

CN- (-1)

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37
Q

permanganate

A

MnO4- (-1)

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38
Q

thiocyanate

A

SCN- (-1)

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39
Q

chromate

A

CrO4 (-2)

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40
Q

dichromate

A

Cr2O7 (-2)

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41
Q

borate

A

BO3 (-3)

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42
Q

What is the rate determining step?

A

the slowest step in the mechanism

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43
Q

What is Arrhenius equation (collision theory)?

A 
k = Ae^-Ea/RT
k = rate constant
A = frequency factor
Ea = activation energy
R = ideal gas constant
T = temperature in kelvins
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44
Q

What does +ΔG mean?

A

endergonic = energy absorbed

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45
Q

What does -ΔG mean?

A

exergonic = energy given off

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46
Q

What effect does lowering the temperature have on the rate of a reaction?

A

it decreases the rate

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47
Q

What effect does adding a catalyst have on the rate of a reaction?

A

it increases the rate

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48
Q

What effect does doubling the concentrations of all the reactants have on the rate of a reaction?

A

zero-order: rate unaffected
first-order: rate doubled
second-order: rate multiplied by 4

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49
Q

What does it mean if Q < Keq?

A

ΔG < 0, reaction proceeds in the forward direction

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50
Q

What does it mean if Q = Keq?

A

ΔG = 0, reaction is in dynamic equilibrium

51
Q

What does it mean if Q > Keq?

A

ΔG > 0, reaction proceeds in the reverse direction

52
Q

If a reaction is endothermic (ΔH > 0) does heat function as a reactant or product?

A

a reactant

53
Q

If pressure is increased, will the reaction shift to the side of the equation with more or fewer moles of gas?

A

when the pressure of a system is increased, the system will react in the direction that produces fewer moles of gas

54
Q

What conditions factor formation of a kinetic product?

A

Kinetic products are factored at low temperatures with low heat transfer

55
Q

What conditions favor formation of a thermodynamic product?

A

Thermodynamic products are favored at high temperatures with high heat transfer

56
Q

On a reaction coordinate diagram, how would the kinetic pathway appear as compared to the thermodynamic pathway?

A

Kinetic pathways require a smaller gain in free energy to reach the transition state. They also have a higher free energy of the products, with a smaller difference in free energy between the transition state and the products.

57
Q

Define an isolated system

A

The system cannot exchange energy (heat and work) or matter with the surroundings; for example, an isolated bomb calorimeter

58
Q

Define a closed system

A

The system can exchange energy (heat and work) but not matter with the surroundings; for example, a steam radiator

59
Q

Define an open system

A

The system can exchange both energy (heat and work) and matter with the surroundings; for example, a pot of boiling water

60
Q

Define isothermal process

A

the system’s temperature is constant
ΔU = 0
Q = W

61
Q

Define a diabatic process

A

no heat is exchanged between the system and the environment; thus the thermal energy of the system is constant throughout the process
Q = 0
ΔU = -W

62
Q

Define isobaric process

A

the pressure of the system is constant

line appears flat in P-V graph

63
Q

Define an isovolumetric (isochoric) process

A

the volume of the system is constant
W = 0
ΔU = Q

64
Q

Define sublimation

A

when a solid goes directly into the gas phase

65
Q

Define deposition

A

when a gas goes directly into the solid phase

66
Q

What is the triple point on a phase diagram?

A

The point at which the three phase boundaries meet, this is the temperature and pressure at which the three phases exist in equilibrium

67
Q

What is the critical point on a phase diagram?

A

Where the phase boundary between the liquid and gas phases terminates, this is the temperature and pressure above which there is no distinction between phases

68
Q

What are standard conditions? When are standard conditions used for calculations?

A

Kinetics, equilibrium, and thermodynamics calculations use standard conditions, which are 25°C (298 K), 1 atm pressure, and 1 M concentrations

69
Q

What is the definition of a state function? List five common state functions

A

State functions are properties of a system at equilibrium and are independent of the path taken to achieve the equilibrium; they may be dependent on one another
examples: pressure (P), density (p), temperature (T), volume (V), enthalpy (H), internal energy (U), Gibbs free energy (G), and entropy (S)

70
Q

What is the definition of a process function?

A

Process functions define the path between equilibrium states and include Q (heat) and W (work)

71
Q

Contrast temperature and heat

A

Temperature is an indirect measure of the thermal content of a system that looks at average kinetic energy of particles in a sample. Heat is the thermal energy transferred between objects as a result of differences in their temperatures

72
Q

Contrast specific heat and heat capacity

A

Specific heat (c) is the energy required to raise the temperature of one gram of a substance by one degree Celsius. Heat capacity (mc) is the product of mass and specific heat and is the energy required to raise any given amount of a substance one degree Celsius.

73
Q

Contrast constant-volume and constant-pressure calorimetry

A

A constant-pressure calorimeter (coffee cup calorimeter) is exposed to constant (atmospheric) pressure. As the reaction proceeds, the temperature of the contents is measured to determine the heat of the reaction. A content-volume calorimeter (bomb calorimeter) is one in which heats of certain reactions (like combustion) can be measured indirectly by assessing temperature change in a water bath around the reaction vessel.

74
Q

What is the specific heat of liquid water (in calories)?

A

cH2O (l) = 1 cal/g(K)

75
Q

Define endothermic and exothermic processes

A

Endothermic reactions involve an increase in heat content of a system from the surroundings (ΔH > 0), while exothermic reactions involve a release of heat content from a system (ΔH < 0)

76
Q

Rank the phases of matter from lowest to highest entropy

A

Solids have the lowest entropy, followed by liquids, with gases having the highest entropy

77
Q

Describe entropy in terms of energy dispersal and disorder

A

Entropy increases as a system has more disorder or freedom of movement, and energy is dispersed in a spontaneous system. Entropy of the universe can never be decreased spontaneously

78
Q

Name some characteristics that make the gas phase unique.

A

Gases are compressible fluids with rapid molecular motion, large intermolecular distances, and weak intermolecular forces

79
Q

A mercury barometer is primarily affected by atmospheric pressure. What would happen to the level of the mercury in the column if the barometer was moved to the top of a mountain? The barometer was placed ten meters under water?

A

At the top of a mountain, the atmospheric pressure is lower, causing the column to fall. Under water, hydrostatic pressure is exerted on the barometer in addition to atmospheric pressure, causing the column to rise.

80
Q

What are the conditions for STP?

A 
T = 273 K (0°C)
P = 1 atm
81
Q

What are the standard conditions?

A 
T = 298 K (25°C)
P = 1 atm
concentrations = 1 M
82
Q

What are the assumptions made by the kinetic molecular theory?

A

Assumptions in the kinetic molecular theory include: negligible volume of gas particles, no intermolecular forces, random motion, elastic collisions, and proportionality between absolute temperature and energy

83
Q

Hydrogen sulfide (H2S), methyl salicylate (C8H8O), and benzaldehyde (C7H6O) are released at the same time from across a room, in which order would one smell the odors?

A

hydrogen sulfide first, benzaldehyde second, and methyl salicylate last. Because all of the gases have the same temperature, they have the same kinetic energy; thus, the lightest molecules travel the fastest.

84
Q

In what way do real gases differ from ideal gases?

A

Real gas molecules have non negligible volume and attractive forces. Real gases deviate from ideal gases at high pressure (low volume) and low temperature.

85
Q

Which gas will exert a higher pressure under the same, non ideal conditions: methane or chloromethane?

A

According to the van Der Waals equation, if a is increased while b remains negligible, the correction (n^2a/V^2) gets larger, and the pressure drops to compensate. Therefore, methane will behave more ideally than chloromethane because a is smaller for methane. The real pressure of methane will thus be higher (closer to ideal).

86
Q

If methane and isobutane are placed in the same size container under the same conditions, which will exert the higher pressure (consider both as having negligible attractive forces)?

A

Isobutane is larger and will thus have a larger correction term for the size of the molecule, b. This makes the term V - nb smaller. The pressure or volume must rise to compensate. Because the two gases are in the same size container, isobutane must exert a higher pressure.

87
Q

Describe the process of solvation

A

Solvation refers to the breaking of intermolecular forces between solute particles and between solvent particles, with formation of intermolecular forces between solute and solvent particles. In an aqueous solution, water is the solvent.

88
Q

Describe the differences between solubility and saturation

A

Solubility is the amount of solute contained in a solvent. Saturation refers to the maximum solubility of a compound at a given temperature; one cannot dissolve any more of the solute just by adding more at this temperature.

89
Q

What is one way in which solubility of a compound can be increased?

A

Solubility of solids can be increased by increasing temperature. Solubility of gases can be increased by decreasing temperature or increasing the partial pressure of the gas above the solvent (Henry’s law)

90
Q

Name two ions that form salts that are always soluble

A

Group I metals, ammonium, nitrate, and acetate salts are always soluble

91
Q

What is the equation for percent composition by mass?

A

mass of solute/mass of solution x 100%

92
Q

What is the equation for mole fraction (X)?

A

Xa = moles of a/total moles of all species

93
Q

What is the equation for molarity (M)?

A

M = moles of solute/liters of solution

94
Q

What is the equation for molality (m)?

A

m = moles of solute/kilograms of solvent

95
Q

What is the equation used for dilution?

A

MiVi = MfVf

i = initial
f = final
M = molarity
V = volume
96
Q

What is the normality (N) of a solution?

A

The normality (N) of a solution is equal to the number of equivalents of interest per liter of solution. An equivalent is a measure of the reactive capacity of a molecule. Most simply, an equivalent is equal to a mole of the species of interest - protons, hydroxide ions, electrons, or ions.

97
Q

What do comparisons of the ion product (IP) to Ksp tell you about the solution?

A

It determines the level of saturation and behavior of the solution:

IP < Ksp: the solution is unsaturated, and if more solute is added, it will dissolve

IP = Ksp: the solution is saturated (at equilibrium), and there will be no change in concentrations

IP > Ksp: the solution is supersaturated, and a precipitate will form

98
Q

Explain the common ion effect.

A

The common ion effect decreases the solubility of a compound in a solution that already contains one of the ions in the compound. The presence of that ion in solution shifts the dissolution reaction to the left, decreasing its dissociation.

99
Q

Explain the formation of a complex ion in solution.

A

The formation of a complex ion in solution greatly increases solubility.

The formation or stability constant (Kf) is the equilibrium constant for complex formations. Its value is usually much greater than Ksp

The formation of a complex increases the solubility of other salts containing the same ions because it uses up the products of those dissolution reactions, shifting the equilibrium tot he right (the opposite of the common ion effect)

100
Q

What is a colligative property?

A

Colligative properties are those that depend on the amount of solute present, but not the actual identity of the solute particles. Examples include vapor pressure depression, boiling point elevation, freezing point depression, and osmotic pressure.

101
Q

How are molality and molarity related for water? How are they related for other solvents?

A

Molarity (M) and molality (m) are nearly equal at room temperature. This is only because 1L solution is approximately equal to 1 kg solvent for dilute solutions (the denominators of the molarity and molality equations, respectively). For other solvents, molarity and molality differ significantly because their densities are not 1 g/ml like water.

102
Q

What are the equations for freezing point depression and billing point elevation?

A

Freezing point depression: ΔTf = iKfm

Boiling point elevation: ΔTb = iKbm

103
Q

What is the equation for osmotic pressure?

A

osmotic pressure = iMRT

104
Q

What is the equation for vapor pressure depression?

A

Raoult’s law: PA = XAP°A

PA = the vapor pressure of solvent A when solutes are present

XA = the mole fraction of the solvent A in the solution

P°A = the vapor pressure of solvent A in its pure state

105
Q

Compare and contrast the three definitions for acids and bases

A

Arrhenius) acid: dissociates to form excess H+ in solution, base: dissociates to form excess OH- in solution

Bronsted-Lowry) acid: H+ donor, base: H+ acceptor

Lewis) acid: electron pair acceptor, base: electron pair donor

106
Q

What is amphoteric?

A

an amphoteric species is one that reacts like an acid in a basic environment and like a base in an acidic environment (H2O)

107
Q

What is amphiprotic?

A

an amphiprotic species is one that can either gain or lose a proton

108
Q

What is the equation to simplify scientific notation log values?

A

p value = m - 0.n

Ex: If the Ka of an acid is 1.8 x 10^-5, then what is its pKa?
Soln: 5 - 0.18 = 4.82 (actual = 4.74)

109
Q

What is an amphoteric species?

A

An amphoteric species can act as an acid or a base

110
Q

If a compound has a Ka value&raquo_space; water, what does it mean about its behavior in solution? How does this compare with a solution that has only a slightly higher Ka than water?

A

High Ka indicates a strong acid, which will dissociate completely in solution. Having a Ka slightly greater than water means the acid is a weak acid with minimal dissociation.

111
Q

If a compound has a Kb value&raquo_space; water, what does it mean about its behavior in solution? How does this compare with a solution that has only a slightly higher Kb than water?

A

High Kb indicates a strong base, which will dissociate completely in solution. Having a Kb slightly greater than water means the base is a weak base with minimal dissociation.

112
Q

What is the mathematical relationship between Ka, Kb, and Kw?

A

Ka x Kb = Kw

113
Q

What species are considered the equivalents for acids and bases?

A

Acids use moles of H+ (H3O+) as an equivalent. Bases use moles of OH- as an equivalent.

114
Q

Calculate the normality of 2 M Al(OH)3 and 16 M H2SO4

A

6 N Al(OH)3

32 N H2SO4

115
Q

Describe the part of a titration curve known as the buffering region.

A

The buffering region occurs when [HA] ~ [A-] and is the flattest portion of the titration curve (resistant to changes in pH).

116
Q

Describe the part of a titration curve known as the half-equivalence point.

A

The half-equivalence point is the center of the buffering region, where [HA] = [A-].

117
Q

Describe the part of a titration curve known as the equivalence point.

A

The equivalence point is the steepest point of the titration curve, and occurs when the equivalents of acid present equal the equivalence of base added (or vice-versa).

118
Q

Describe the part of a titration curve known as the endpoint.

A

The endpoint is the pH at which an indicator turns its final color.

119
Q

For a reaction involving a strong base and a weak acid, what indicator would be best to indicate the endpoint of the titration?

A

one with a pKa = 9.7

120
Q

In which part of the pH range (acidic, basic, or neutral) will the equivalence point fall for the titration of a strong acid + weak base?

A

acidic range

121
Q

In which part of the pH range (acidic, basic, or neutral) will the equivalence point fall for the titration of a strong base + weak acid?

A

basic range

122
Q

In which part of the pH range (acidic, basic, or neutral) will the equivalence point fall for the titration of a strong acid + strong base?

A

neutral range (pH = 7)

123
Q

In which part of the pH range (acidic, basic, or neutral) will the equivalence point fall for the titration of a weak acid + weak base?

A

can have an equivalence point in the acidic, neutral, or basic range, depending on the relative strengths of the acid and base.

124
Q

What is the purpose of a buffer solution?

A

A buffer solution is designed to resist changes in pH and has optimal buffering capacity within 1 pH point from its pKa.

MCAT (9 decks)

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