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MCAT Prep > General Chemistry > Flashcards

General Chemistry Flashcards

1
Q

Atomic number

A

number of protons, if this changes you have a new element

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2
Q

Mass number

A

total mass of protons plus neutrons

subtract atomic number from mass number to find the number of neutrons in a molecule

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3
Q

What are isotopes used for?

A

track chemical reactions

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4
Q

How to name elements with more than one cation (transition metals)

A

use roman numerals

use -ous prefix for smaller charge and -ic prefix for greater charge

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5
Q

Naming oxyanions

A

hypo- -ite (2 less)
-ite (1 less)
-ate (normal)
per- -ate (more)

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6
Q

Pauli Exclusion Principle

A

no two electrons in an atom can have exactly the same four quantum numbers

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7
Q

Ranking of orbitals, shells and subshells

A

Shells are periods (n=1, 2, 3 …)

Subshells are s,p,d,f (n=1 only has the s subshell)

Orbitals are within the subshells and can hold 2 electrons (s can have 1 orbital, p can have 3 orbitals)

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8
Q

Aufbau principle

A

electrons fill lower orbitals first

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9
Q

Hund’s rule

A

fill orbitals half full first

(everyone wants own seat on the bus)

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10
Q

Group 1 elements

A

alkali metals

highly reactive

good cations

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11
Q

Group 2 elements

A

alkaline earth metals

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12
Q

Group 6 elements

A

chalogens

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13
Q

Group 7 elements

A

halogens

often found as diatomic molecules to form complete valence shell

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14
Q

Trends with Zeff

A

increases across periodic table (more protons with no new shell electrons)

decreases down periodic table (more protons but also more shell electrons to block Zeff)

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15
Q

Trends with radius

A

decreases across periodic table since Zeff is increasing

increases down periodic table

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16
Q

Trends with electronegativity

A

increases across periodic table

decreases down periodic table

same as Zeff

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17
Q

Are anions bigger or smaller than neutral atom?

A

bigger

more electrons = more electrostatic repulsion

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18
Q

Are cations bigger or smaller than neutral atom?

A

smaller

less electrons = less repulsion and greater Zeff

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19
Q

Ionization energy

A

amount of energy to remove electron from atoms

first electron always the easiest to remove

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20
Q

Which bonds can lead to H-bonding?

A

-FH -OH and -NH bonds

especially electronegative bonds

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21
Q

Combustion reaction

A

a compound burns in the presence of oxygen

highly exothermic

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22
Q

Does a reaction with a +H make the surrounding area warmer or colder?

A

+H indicates an endothermic reaction

takes heat from the environment to drive reaction

makes the surrounding area colder

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23
Q

Does increasing temperature speed up all reactions?

A

No. Only speeds up endothermic reactions where heat acts like another reactant

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24
Q

Neutralization reaction

A

Acid + Base –> H2O + Salt

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25
Q

Intramolecular forces

A

ionic bonds, covalent bonds, metallic

bonds within a molecule

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26
Q

Intermolecular forces in order of increasing strength

A 
London dispersion forces
Dipole-dipole interactions
H-bonds
Ionic-dipole interactions
Ionic interactions
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27
Q

What is a stronger bond ionic or covalent?

A

ionic

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28
Q

Do larger or smaller molecules have greater London dispersion forces? Why?

A

Larger molecules. More probable for a temporary random dipole to form

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29
Q

what is a biological example of an intermolecular force?

A

peptide hormone temporarily associating with a membrane receptor

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30
Q

Which atoms do not follow the octet rule?

A

Sulfur and phosphorous can have expanded octet

Hydrogen is stable with 2 valence e

Helium has max 6 valence e

Boron has max 5 valence e

Be has max 4 valence e

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31
Q

Which molecule has greater bond angles water or methane?

A

Methane

Water has two lone pairs that make it’s bonds squish together

Methane can be in the tetrahedral formation with 109.5º between its bonds

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32
Q

Difference between trigonal planar and trigonal pyrimidal?

A

trigonal planar has no lone pairs

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33
Q

When do we see sp hybridization?

A

triple bonds

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34
Q

When do we see sp3 hybridization?

A

Four bonds

Ex: in a methyl group

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35
Q

When do we see sp2 hybridization?

A

ex: a carbonyl group

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36
Q

What is the hybridization of the central carbon in CO2?

A

sp

has two regions of electron density

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37
Q

If pH is greater than pKa what happens?

A

since the solution is more basic, the molecule is in conjugate base form and deprotonated

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38
Q

If pH is less than pKa what happens?

A

since the solution is more acidic, the molecule is in conjugate acid form and protonated

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39
Q

What are the common diatomic molecules?

A

Have No Fear Of Ice Cold Beer

hydrogen, nitrogen, flourine, oxygen, iodine, chloride, bromine

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40
Q

What do most oxidizing agents generally include?

A

Cr and O

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41
Q

What is an example of a weak oxidizing agent?

A

PCC

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42
Q

What are examples of reducing agents?

A

NaBH4, NaH, LiAlH4

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43
Q

When can reducing agents be biochemically used?

A

to break disulfide bonds

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44
Q

What is hydrogen’s general oxidization state?

A

+1

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45
Q

What is oxygen’s general oxidization state?

A

-2

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46
Q

What is the carbonyl carbon’s oxidization state in carboxylic acid?

A

+3

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47
Q

When do redox reactions occur?

A

when at least one specie’s oxidization state changes

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48
Q

When glucose is converted into two molecules of pyruvate during glycolysis what happens?

A

the carbon is oxidized

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49
Q

How do titrations work in general?

A

1) take a known volume of solution and use add another substance of a known concentration to it
2) when substance starts changing color, you know that moles of the added substance = moles of substance of interest
3) can set M1V1 = M2V2, where V2 is how much volume of the known substance was added
4) solve for concentration of the unknown substance

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50
Q

What is true at the equivalence point of a titration?

A

at the equivalence point moles are equal

*the vertical line portion

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51
Q

What is true at the half equivalence point of a titration?

A

pH = pKa

*middle of horizontal line

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52
Q

What are titrations used for?

A

to find an unknown concentration in solution

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53
Q

What is the change in enthalpy equal to?

A

the heat of a reaction

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54
Q

What are standard conditions?

A

25ºC, 300K, 1 atm

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55
Q

What is the enthalpy of formation of Cl2?

A

0 kJ/mol

no heat needed to produce pure elements

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56
Q

Do you need energy to create bonds?

A

no

energy is released when bonds are formed

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57
Q

Do you need energy to break bonds?

A

yes

need to put energy in to break bonds

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58
Q

What is Keq equal to?

A

products / reactants

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59
Q

What happens when Keq is >1?

A

products are favored

∆G is negative (spontaneous) in the forward direction

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60
Q

What happens when Keq is <1?

A

reactants are favored

∆G is positive (nonspontaneous) in the forward direction

61
Q

What happens when Keq =1?

A

We are at equilibrium at ∆G = 0

62
Q

What is Q?

A

the equilibrium at any point

63
Q

What happens when Q

A

have too many reactants, equilibrium shifts to the products

64
Q

What happens when Q>Keq?

A

have too many products, equilibrium shifts to the reactants

65
Q

Is the thermodynamic or kinetic product favored at high temperatures?

A

the thermodynamic product

have enough energy to overcome activation barrier and create the more stable product

66
Q

Is the thermodynamic or kinetic product favored at low temperatures?

A

the kinetic product

don’t have enough energy to form the more thermondynamically stable product so we make the less stable, kinetic product

67
Q

Relationship between pressure and boiling point

A

lower pressure means a lower boiling point because it is easier for liquid molecules to “spread out” into gas phase

68
Q

analyte

A

compound/molecule being investigated

69
Q

Avogadro’s number

A

6e23 atoms (or units) per one mole

70
Q

What are ways (5) that an enzyme can catalyze a reaction?

A

1) stablize the T-state
2) change the orientation of a molecule
3) weaking bonds within reactants
4) increase frequency of collisions
5) donate ED to the reactants

71
Q

heterogenous catalysts

A

in a different phase than the reactants

often a solid phase catalyze will absorb liquid/gas reactants

72
Q

homogenous catalysts

A

in the same phase as the reactants

73
Q

In endothermic reactions, are the products or the reactants higher in energy?

A

the products

have to add energy to get to the products

74
Q

rate law

A

mathematical expression for the relationship between reactant concentrations and the rate of a reaction

75
Q

What is the example of a zero order reaction?

A

an enzyme that is saturated

the rate is not dependent on the reactants, dependent on the enzymes since saturated

76
Q

What rates are important for determine a rate law?

A

the initial rates of a reaction

77
Q

How do you find Zeff?

A

subtract the shell electrons from the number of protons

78
Q

What signifies a better oxidizing agent?

A

more likely to reduce

79
Q

Why does reduction happen at the cathode?

A

a molecule can gain electrons from the negatively charged cathode

80
Q

What should not be included in Keq?

A

pure liquids and solids

81
Q

Does temperature affect equilibrium of exothermic reactions?

A

Yes

temperature is a product in exothermic reactions

so decreasing the temperature, will shift the reaction towards the products

82
Q

If you only have the total sample mass can you determine the molecular formula?

A

no

can only find the empirical formula

need the molecular mass to find the molecular formula

83
Q

How can you find the yield of a product using stoich?

A

1) convert starting grams to moles
2) divide moles of regants by coefficient
3) after step 2, the smaller number is the limiting reagant
4) determine how many moles of product you will have
5) solve for total mass of product

84
Q

examples of amorphous solids

A

glass, gel, plastic

have less structure than crystalline solids

85
Q

molecular solids

A

a type of crystalline solid held together by intermolecular forces

86
Q

network solids

A

a type of crystalline solid held together by covalent bonds

87
Q

viscosity

A

resistance of liquid to flow

higher viscosity = slower flow

88
Q

what is surface tension created by?

A

intermolecular forces between water molecules at surface

89
Q

cohesive forces versus adhesive forces

A

cohesive forces are between the same molecules

adhesive forces are between different molecules

90
Q

formula and units for pressure

A

pressure = force/area

Pa = N/m2

91
Q

fusion

A

solid to liquid phase transition

92
Q

sublimation

A

solid to gas phase transition

93
Q

deposition

A

gas to solid phase transition

94
Q

What is happening on flat lines of a heat curve?

A

on the flat lines a phase transition is happening. so look at change in enthalpy

95
Q

What is happening on the sloped lines of a heat curve?

A

adding heat to same phase

use Q=mc∆T formula

96
Q

Balmer series

A

hydrogen emission lines corresponding to transitions from higher levels to n=2

in the visible spectrum

97
Q

Lyman series

A

hydrogen emission lines corresponding to transitions from higher levels to n=1

in the UV wavelengths

98
Q

Order of wavelengths from shortest to largest

A 
gamma rays
X rays
UV
visible light
infrared 
microwave
radiowaves
99
Q

What does kinetic molecular theory tell us?

A

gas particles are in constant motion and exhibit perfectly elastic collisions

100
Q

2 assumptions of ideal gases

A

1) gas particles have no volume

2) gas particles experience no attraction or repulsion

101
Q

When do gases behave more like “ideal gases”?

A

at high temperatures, high volumes, and low pressures

102
Q

What units does temperature need to be in when working with gases?

A

Kelvin

K = ºC + 273

103
Q

Molar volume

A

1 mole of gas occupies 22.4 L at STP

104
Q

STP versus thermodynamic conditions

A

STP (gas): T=273K

Thermodynamic: T= 298K

105
Q

If we have two ideal gases of the same moles at STP, will the two gases occupy the same volume? Why?

A

yes, because ideal gases act as if they do not have their own volume

106
Q

Do real gases have greater or lower pressure/volume than ideal gases at STP?

A

real gases have lower pressure/volume at STP since real gases can attract each other, resulting in lower volume

107
Q

Do real gases have greater or lower pressure/volume than ideal gases at extreme conditions?

A

greater pressure/volume at extreme conditions

108
Q

What would effuse first CO2 or H2?

A

H2 since it is smaller

Graham’s law predicts this

109
Q

If you decrease the volume of a reaction vessel, how would the equilibrium shift?

A

decreased volume means increased pressure

shift to side of reaction with fewer moles of gas to decrease pressure

110
Q

If you decrease the pressure of a reaction vessel, how would the equilibrium shift?

A

shift to side of reaction with more moles of gas to increase pressure

111
Q

Arrhenius acid

A

acids dissociate to form H+ ions

112
Q

Arrhenius base

A

bases dissociate to form OH- ions

113
Q

Bronsted-Lowry acid

A

an acid is a proton donor

114
Q

Bronsted-Lowry base

A

a base is a proton acceptor

115
Q

Lewis acid

A

an acid is an electron acceptor

116
Q

Lewis base

A

a base is an electron donor

117
Q

Difference between Bronsted-Lowry and Lewis definitions

A

Bronsted-Lowry definition refers to protons

Lewis definition refers to electrons

118
Q

Amphoteric species

A

can act as acids or bases

119
Q

Kw

A

equilibrium constant for the auto-ionization of water

120
Q

What is the formula for Kw?

A

Kw = [H3O+][OH-]

121
Q

What does Kw equal at standard conditions?

A

1*10^-14

122
Q

What happens to Kw if we raise the temperature?

A

Kw increases

auto-ionization of water is an endothermic process

123
Q

What do salts do to the boiling point of water?

A

they increase the boiling point

124
Q

What do salts do the freezing point of water?

A

they decrease the boiling point

125
Q

If the vapor pressure of a liquid decreases, what happens to the boiling point?

A

it increases since it takes more heat to get the vapor pressure up to the atmospheric pressure

126
Q

What are the four colligative properties?

A

1) vapor pressure reduction
2) boiling point elevation
3) freezing point depression
4) osmotic pressure

127
Q

What is vapor pressure?

A

pressure gas exerts above the liquid phase

128
Q

Vapor pressure change formula

A

P = XaPa

129
Q

As the mol fraction of solvent decreases what happens to the solvent’s vapor pressure?

A

it decreases since there are less moles of solvent compared to moles of solutes

130
Q

What is the boiling point elevation formula?

A

∆Tb=iKbm

131
Q

What is the freezing point elevation formula?

A

∆Tb=iKfm

132
Q

Molarity in water versus molality in water

A

Molarity in pure water is roughly equal to the molality

133
Q

What values have to be used for colligative properties?

A

molality and the number of dissolved particles!

134
Q

What is the standard reduction potential measured in?

A

Volts

135
Q

If the reduction potential is more positive?

A

the reduction is more likely to happen spontaneously

136
Q

What is true of all electrochemical cells?

A

anode is site of oxidation
cathode is site of reduction

electrons move from anode to cathode

137
Q

How to remember anode versus cathode

A

An Ox Red Cat

138
Q

Galvanic cell

A

spontaneous redox reaction is used to generate a positive potential difference that drives a current

Eºcell must always be positive

139
Q

Cathode and anode in galvanic cell

A

Cathode is positive since electrons move towards it spontaneously and anode is negative

140
Q

Daniell cell

A

a common galvanic cell

electrons pass through a wire

salt bridge allows spectator ions to travel between the half cells and balances charge

141
Q

Concentration cell

A

a type of galvanic cell

solutions aren’t separated

electrodes made out of the same material

2 regions have a concentration difference

142
Q

Electrolytic cells

A

electrical input is used to drive a nonspontaneous redox reaction

Eºcell is negative

143
Q

Anode and cathode in galvanic cell

A

Cathode is negative since electrons do not spontaneously go to it

anode is positive

144
Q

What type of cells are biological cells like SDS page?

A

electrolytic

negative charges move towards positive anodes

145
Q

Rechargable batteries

A

when discharging, battery acts like a spontaneous galvanic cell

when recharging, battery acts like a nonspontaneous electrolytic cell that requires energy

146
Q

Nernst equation

A

helps account for how electric potential of a cell is affected by temperature and concentration of reactants

E’cell = Eºcell - 0.06/z*log(Q)

147
Q

Relationship between Q and E’cell

A

As Q increases and products increase, E’cell decreases and is less spontaneous

148
Q

Relationship between ∆G and Eºcell

A

∆G= -nFEºcell

MCAT Prep (22 decks)

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