1
Q
Which are stronger Intermolecular or Intramolecular forces?
A
Intramolecular forces are physical and stronger
2
Q
What determines physical properties?
A
intermolecular forces determine physical properties
3
Q
How do intermolecular forces affect physical properties?
A
- More polar = higher boiling point
- More electrons = higher london dispersion forces
- Bigger molecule = higher LDF making it harder to break
4
Q
What does n, l, ml and ms mean?
A
- n: shell
- l: subshell
- ml: orbital
- ms: direction of spin
5
Q
What is the Pauli Exclusion principle?
A
No two electrons can have the same 4 quantum numbers + Electrons cannot spin the same direction in an orbital
6
Q
What is the Aufbau principle?
A
Electrons are added to the lowest possible energy orbital available in an atom or ion before being added to higher ones
7
Q
What is Hunds rule?
A
The positive electron occupies each orbital first before going back and filling the second electron space with a negative electron.
8
Q
Why do we emphasize the valence electrons in an atom when discussing atomic properties?
A
Valence electrons are responsible for properties like bonding
9
Q
What is the Anion rule for electron configuration?
A
Add the electrons needed
Ex. O: 1s2,2s2,2p4
O-2: 1s2,2s2,2p6
10
Q
What is the Cation rule for electron configuration?
A
Remove electrons from the orbital with the highest n value
11
Q
What are excited electrons?
A
electrons that have gained energy and have jumped to a higher energy orbital (total number of electrons stay the same)
12
Q
What is the formal charge?
A
hypothetical charge of an atom within a molecule
13
Q
What does isoelectric mean?
A
same number of electrons
14
Q
How does Quantum Theory explain ionic bonding?
A
Transfer of electrons from one orbital to another
(from the metal to the non-metal)
15
Q
How does the valence bond theory explain how covalent bonds are formed?
A
The model theorizes that a covalent bond forms when two orbitals overlap to produce a new combined orbital containing two electrons of opposite spin.
16
Q
Where is the shared electron pair most likely to be found?
A
The shared electron pair is most likely to be found in the space between the two nuclei of the atoms forming the bonds.
17
Q
Does orbital overlapping result in an increase or decrease in energy?
A
This overlapping results in a decrease in the energy of the atoms forming the bond. (having an orbital with only one electron is a higher energy state)
18
Q
What is hybridization?
A
Hybridization is the process of forming hybrid orbitals of at least two different orbitals (must be done for bonding)
- Creating a hybrid orbital where all the electrons are of the same energy level
19
Q
What is a sigma bond?
A
a bond created by the end-to-end overlap of atomic orbitals
20
Q
What is a pi bond?
A
a bond created by the side by side (or parallel) overlap of two un-hybridized p orbitals (one from each neighboring atom).
21
Q
what does a double bond contain? triple bond?
A
- double bond: 1 sigma 1 pi
- Triple bond: 1 sigma 2 pi
- both are partial hybridization
22
Q
What is an expanded octet?
A
An expanded octet is an exception to the octet rule where a central atom in a Lewis structure has more than eight electrons in its valence shell.
- For hybridized orbitals, must use d orbitals in the hybrids
23
Q
What is the VSEPR Theory?
A
A model used to predict the 3-dimensional geometry of molecules based on the repulsion of the bonding and non-bonding electrons in the molecule.
24
Q
What is the assumption in the VSEPR theory?
A
Atoms in a molecule are bound together by pairs of electrons 🡪 bonding pairs
25
How do lone pairs position themselves on atoms in molecules?
- Pairs of electrons around any particular atom position themselves as far apart from each other as possible (as to minimize the repulsion between bonding and non-bonding pairs)
- Lone pairs occupy slightly more space than bonding electron pairs (so they push bonding pairs away, decreasing their bond angle by 2.5°)
26
How is shape of a molecule determined?
The shape is determined by the number of bonding and non-bonding electrons in the molecule. Lewis diagram must be drawn first.
27
What is the difference between electron and molecular geometry?
- Electron geometry is the general shape of electron groups but is often not the shape of the molecule
- Molecular geometry is the position of only the atoms in the molecule (not bonding pairs)
28
What are vectors?
A vector is a bond dipole used to represent polar covalent bonds pointing towards the more electronegative atom.
- to obtain final resultant vector, add vectors
29
What are the 4 types of solids?
Ionic, metallic (metals cu), molecular (non-metals polar and non-polar), and covalent network (metalloids/carbon)
30
What are ionic crystals made up of and it's properties?
- consisting of 3D arrangement of positive and negative ions in a crystal lattice structure
- Hard but brittle (if struck, becomes distorted and repel)
- high melting points (due to very strong electrostatic forces)
- Soluble in water and conducts electricity in liquid (ions conduct better)
31
What is the structure of metallic crystals?
- solids with closely packed atoms held together by electrostatic interactions and free moving electrons
32
What is the electron sea model theory?
- states that the electrons in a metallic crystal move freely around the fixed positively charged nuclei
33
What is metallic bonding?
bonding that holds the nuclei and electrons of metal together
34
How are metallic ions pack closely together?
Pack as close as possible because of strong electrostatic forces between the ions and the free moving electrons
35
What are the properties of metallic crystals?
- Have low ionization energy and easily give up electrons
- Sheen due to mobile valence electrons absorbing and emitting light
- malleable due to the electron sea allowing electrons to slide over each other
- Electrical conductivity due to free moving electrons (when metal is connected to a battery)
- hardness due to the electron sea surrounding nuclei producing strong electrostatic attractions that hold nuclei together
36
What are molecular crystals made of?
- composed of individual molecules held together by intermolecular forces
- can be polar or non-polar
37
What are the properties of molecular crystals?
- low melting point due to intermolecular interactions
- little hardness due to intermolecular forces
- bad with electrical conductivity when composed of non-polar molecules, some (not all) polar compounds when dissolved can ionize
38
What are covalent network crystals?
atoms form covalent bonds in an interwoven network (ex. diamond, graphite, silicon carbide)
39
What are the properties of covalent network crystals?
- Very high melting points
- Extreme hardness
- insoluble
- not good conductors of electricity
40
Compare diamond and graphite
- diamonds: huge network of C-C linkage (all 4 carbon bonds are equal in strength)
- Graphite: carbons only use 3 electrons to bond with adjacent carbons
- has a layer of carbon that isn't bonded
- unused electrons can move freely (explains why graphite can conduct electricity)
- layers are held together by weak LDF + can slip over each other (weak in 3D but strong in 2D)
41
Compare glass and quartz
- have the same chemical formula but glass lacks long-range, regular crystalline structure of quartz making it weak
42
What is the Bose-Einstein condensate?
Bose–Einstein condensate (BEC) is a state of matter that consists of a pile of atoms all in the same place at the same time and exists only at temperatures within a few billionths of a degree of absolute zero, which is 0 K or −273.15 °C.
43
What is organic chem?
study of organic compounds which are based on carbon backbones (hydrocarbons)
44
What are the characteristics of carbon molecules containing single bonds?
- saturated
- nonreactive because of strong bonds (hard to break)
45
What are the characteristics of carbon molecules containing double and triple bonds?
- unsaturated: the double and triple bonds are easier to break since additional electrons in the bond are more loosely bound to the nuclei
- more reactive
46
What is an organic compound vs inorganic?
Organic:
- carbon bonded to carbon, hydrogen, oxygen, nitrogen, sulfur and/or phosphorus
Inorganic:
- substance lacking carbon-hydrogen bonds
47
What are isomers?
molecules that have the same molecular formula but their atoms are in a different arrangement
48
What are the types of hydrocarbons?
- saturated: hydrocarbons only contain single bonds
- unsaturated: hydrocarbons containing carbons double or triple bonded
- cyclic: hydrocarbon chains that form rings
- Aromatic: compounds containing only carbon and hydrogen based on aromatic benzene ring
49
What are functional groups and main components?
Functional groups: groups of atoms attached to the hydrocarbons
- Carbon-carbon multiple bonds
- Carbon and more electronegative atoms singlely bonded: stronger intermolecular forces, higher melting and boiling points
- Double bonded carbon and oxygen: higher melting and boiling points
50
What is an Alkane and what are the physical properties?
A hydrocarbon with only single bonds between carbon atoms.
Physical properties:
- non-polar/not water-soluble since attractive forces between alkane molecules>between alkane and water
- soluble in other non-polar solvents
- contain mostly LDF (weak)
- highly branched chain molecules have lower boiling points than straight chains because they have less surface area
51
What are Alkenes what are the physical properties?
A hydrocarbon with at least one double bond between carbon atoms.
- Very similar to alkanes of the same molar mass
- Melting points, boiling points, solubility and densities are very much like those of comparable alkanes (ie. alkanes of the same number of carbon atoms)
- With two fewer H atoms, alkenes have a slightly lower boiling point than their comparable alkanes
52
What is an Alkyne what are the physical properties?
A hydrocarbon with at least one triple bond between carbon atoms.
- Very similar to alkanes of the same molar mass
- Melting points, boiling points, solubility and densities are very much like those of comparable alkanes (ie. alkanes of the same number of carbon atoms)
- With two fewer H atoms, alkenes have a slightly lower boiling point than their comparable alkanes
53
What is an alkyl group?
a carbon group that “branches off” of the main chain
54
What is an aldehyde and what are their properties?
- when the carbonyl group is attached to the end carbon
- Carbonyl group is polar
- lower boiling points/less soluble in water than alcohols
- more soluble in water than hydrocarbons
55
What is an aromatic hydrocarbon and properties?
A compound with a structure based on a benzene ring; a ring of 6 carbons and 3 alternating double bonds
- non-polar, with van der Waals forces (weak) of attraction London dispersion forces
- low solubility in water
- low melting and boiling points
56
What are the types of alcohol?
- Primary alcohol: the carbon the -OH group is attached to, is attached to only one other carbon atom
- Secondary alcohol: the carbon the –OH group is attached to, is attached to only two other carbon atoms
- Tertiary alcohol: the carbon the –OH group is attached to, is attached to only three other carbon atoms
57
What are aromatic alcohols?
an alcohol that contains a benzene ring (these are called phenols). they are used in preparation of plastics, drugs, etc.
58
What are the properties of alcohol?
- hydroxyl group is polar, allows for hydrogen bonding (soluble in water)
- higher melting/boiling points (LDF and hydrogen bonding)
- as the hydrocarbon chain increases in length, solubility in water decreases (More LDF -> non-polar)
59
What are organic halides and what are their properties?
A compound of carbon and hydrogen in which one or more hydrogen atoms have been replaced by halogen atoms
- carbon-halogen is polar
- increased polarity
- higher boiling/melting point
60
What are ethers and what are their properties?
Ethers are compounds where both sides of an oxygen is bound to an alkyl group
- much less polar (no HB)
- good solvents (mix with both polar/non-polar)
- lower melting/boiling points
- very flammable but chemically inert (stable at certain conditions)
61
What are aldehydes and their properties?
- when the carbonyl group is attached to the end carbon
- polar (D-D and LDF)
- Lower boiling points and less soluble in water than alcohols
- More soluble than hydrocarbons in water
- Mix with both polar and non-polar substances (solvents)
62
What are ketones and their properties?
- when the carbonyl group is attached to any of the carbons in the parent chain that is not an end carbon
- polar (D-D and LDF)
- Lower boiling points and less soluble in water than alcohols
- More soluble than hydrocarbons in water
- Mix with both polar and non-polar substances (solvents)
63
What is an oxidation reaction and how does it relate to aldehydes and ketones?
a reaction in which there is a gain of bonds to oxygen or loss of hydrogen atoms (loss of electrons)
- oxidizing agents like hydrogen peroxide, potassium permanganate are used in sulfuric acid for these reactions
- aldehydes and ketones can be prepared through controlled oxidation of alcohols
64
What happens when a primary, secondary and tertiary alcohol is oxidized?
- primary: aldehyde is produced (water byproduct)
- secondary: ketone is produced (water byproduct)
- tertiary alcohols do not undergo this type of oxidation (no hydrogen atom is available to remove)
65
What is hydrogenation in relation to aldehydes and ketones?
- carbonyl group undergoes additional reactions with hydrogen, happens at high temperatures and pressures with a metal catalyst
- aldehyde/ketone + H2 (g) -> alcohol
- reversal of oxidation and is called a reduction reaction
66
What are carboxylic acids and their properties?
- weak acids (ex. lactic acid, found in fruits)
- have distinctive odours
- combines both a carbonyl with an alcohol group
- Polar (H-B, D-D, LDF)
- Can be distiguished using litmus paper (turns orange)
- Higher melting points
67
How are carboxylic acids prepared?
- further controlled oxidation of an aldehyde results in the formation of a carboxylic acid
- the carbonyl group gains another oxygen to form a hydroxyl group on the terminal carbon
68
How do breathalyzer tests work?
- Chromate when in it's oxidized state is Cr+6 and the colour orange
- when air containing ethanol passes through, it oxidizes to form ethanoic acid
- oxidization reduces the chromate ion to Cr+3 which has a green colour
- more green means more alcohol in the breath
69
Why can't ketones be oxidized to form a carboxylic acid?
Since ketones are not on the terminal carbon, a carboxyl group cannot form of that part (octet is full)
70
What are esters and their properties?
- contain ester bonds (carbonyl group bonded to an O)
- responsible for fruit and flower odours
- esters are salts of carboxylic acids and alcohols
- the ester bond is less polar and less soluble in water/lower melting points than carboxylic acids
- gases at room temp, lower molecular mass
71
How are esters prepared?
- Formed by a condesation reaction between a carboxylic acid and an alcohol (called esterfication) with a byproduct of water and H2SO4 as a catalyst
72
What is hydrolysis (saponificaion and water) relating to esters?
- Saponification: esters being treated with an acid or base (usually NaOH) to split the ester into its acid and alcohol (name the acid a sodium salt)
- can use water to split the ester as well (a soap is not produced) (use H2SO4 as a catalyst)
73
What are amines and properties?
- derived from ammonia
- contain a nitrogen bound to an alkyl group and/or hydrogen atoms
- higher B/M points but lower than alcohols
- smaller amines are readily soluble in water due to H-B and D-D
- higher solubility in water when N-H bonding is present
74
How are amines prepared?
- made through the reaction between ammonia (NH3) with an alkyl halide which mades a primary amine
- this can be done further with the primary amine and another alkyl, a secondary amine is formed
- can be done further for a tertiary amine to be formed
75
What are amides and properties?
- carbonyl functional group bonded to a nitrogen atom
- forming and breaking of the bonds in amides relate to peptide bonds
- weak acids, generally insoluble in water
- slightly soluble in water when H-B is present in N-H bonds
- When N is bonded to two Hydrogens, higher BP and MP
76
How are amides prepared?
- carboxylic acid is reacted with ammonia or a primary/secondary amine (condesation and water is a byproduct) (h2So4 is a catalyst)
- Amides can be hydrolyzed in H2So4 to produce a carboxylic acid and an amine (reversal)
77
What are the reactions of alkanes?
- combustion reaction: hydrocarbons exposed to oxygen to produce CO2(g) and H2O(g)
- substitution reactions: hydrogen bonds being substituted for halogen atoms
78
What are the reactions of alkenes and alkynes?
- addition reactions: a hydrogen (hydrogenation) or halogen (halogenation) is added to the double or triple bond
*Markovikov's Rule: when hydrogen halides or water are added to alkenes/alkynes, hydrogen atoms are bonded to the carbon within the double/triple with the most hydrogen atoms (hydrohalogenation H-X or Hydration with water)
79
What are the reactions of aromatic hydrocarbons?
- Substitution *not addition*
- Benzene react with Br2 to which produces 3 possible isomers
- reacts with nitric acid in the presences of sulfuric acid to for nitrobenzene
- reacts with alkyl halides in the presence of an aluminum halide so the alkyl group attatches to the benzene ring
80
How are alkenes prepared from alkyl halides (elimination)?
- Alkyl halides can eliminate a hydrogen and a halide ion from adjacent carbon atoms and form double bonds
- The presence of a hydroxde ion (like NaOH) is required
81
What are the products of oxidizing an alcohol?
an aldehyde/ketone and water
82
What is an example of a reducing agent?
H2
83
What are polymers?
- long molecule made by linking of many smaller molecules called monomers
- can be made of one type or combination of different monomers
84
What are the types of polymers?
- Synthetic polymers: manmade, polymers that can be heated and moulded are called plastics, can be used to make fabrics (polyester)
- Natural Polymers: in living systems like cotton, wool, linen, Ex. polysaccharide
85
What is addition polymerization?
- reaction where alkene monomers are joined through multiple addition reactions to form the polymer
- Ex. Polyacrylamide gel (has cross-links)
86
What is polymer cross linking?
- polymer chains being linked together through cross linking to form networks
- more cross linking -> chains held tight together -> stronger, inflexible
87
What is condensation polymerization?
- monomers combined through multiple condensation reactions forming polymer
- each monomer MUST have two functional groups
- esters can form at both ends of monomers (called polyesters)
88
What are polyamides?
- repeating amide functional groups
- formed from one monomer with a carboxyl group at both ends, and one with amine group at both ends
- Ex. Kevlar
- Ex. Proteins: natural polyamide (amino acids)
89
Why are the signs for the rate of reactants and products different?
- since reactants are being consumed, their concentration is decreasing which makes it negative
- since products are being formed, their concentration is increasing which makes it positive
90
What is thermochemistry?
study of the energy changes with a physical, chemical and/or nuclear change of a system
91
What is kinetic and potential energy?
- Kinetic: energy of motion (anything moving has kinetic energy)
- Potential: stored energy due to the bonds or positon of object
92
What is a system and surroundings?
- system: sample being observed
- surroundings: all matter around the system capable of absorbing/releasing thermal energy
- interactions between the two involved exchange of energy/matter
93
What is the 1st law of thermodynamics?
total energy of the universe is constant
94
What are chemical systems and the 3 types?
- set of reactants and products undergoing transformations
1. Open: can exchange matter/energy with surroundings
2. Closed: can exchange energy but not matter
3. Cannot exchange anything (ideal)
95
What is the difference between heat and temperaure?
- Heat: amount of energy transferred between substances, systems, or surroundings
- Temperature: average kinetic energy of the particles in a system
96
What is the 2nd law of thermodynamics?
- when two objects are in thermal contact, heat is transferred from object with higher temp to object with lower til they are both the same temp
97
What is Calorimetry?
- experimental technique for measuring heat energy changes in chemical system
- calorimeter is used for measuring the heat of the reaction
98
What assumptions are made with calorimetry?
- thermal energy exchanged with the calorimeter cups, thermometer, lid can be ignored
- despite substance being dissolved in water, the properties of the water are not affected
- process takes place under constant pressure
99
What is specific heat capacity?
The specific heat capacity (c) is the amount of heat energy that is needed to raise the temperature of 1 gram of a substance 1oC (or 1 K).
- depends on type of substance/state of substance
100
What is enthalpy, enthalpy change and molar enthalpy?
- The total amount of thermal energy in a substance
- The energy released to or absorbed from the surroundings during a chemical or physical change
- Energy change (absorbed or released) per one mole of a particular reactant or product
101
What assumptions are made with calorimetry when finding molar enthalpy?
- No heat transfer between calorimeter & the outside environment
* Any heat absorbed/released by the calorimeter material is negligible
* A dilute aqueous solution is assumed to have the same density and specific heat capacity equal to that of pure water (D = 1.00 g/mL and c = 4.18 J/goC)
- The water of a calorimeter is considered the surroundings and the container in which the process occurs is the system
102
What are the 4 ways enthalpy changes can be represented?
- Part of a thermochemical equation
- By writing a chemical equation and stating its enthalpy change
- by stating the molar enthalpy of a specific reaction
- drawing an enthalpy change diagram
103
What does enthalpy change depend on?
- For physical and chemical processes, it depends only on reactants and products
- enthalpy change is independent of the process and number of steps to complete
104
What is Hess's Law?
- The value of ∆H for any reaction that can be written in steps equals the sum of the values of ∆H for each individual step in a multistep reaction (ie. it is an additive property)
change of the target equation.
105
What does the slowest step of a reaction tell you?
- the rate determining step (overall rate of the reaction depends on the slowest step)
- to speed up a reaction, focus on this step
- takes the longest and has the greatest Ea
106
What is an intermediate and catalyst?
- Intermediate: starts as product then used as a reactant
- Catalyst: starts as a reactant then produced as a product
107
what are the 2 requirements for reaction mechanisms?
- the equations for the elementary steps must sum to give the overall equation
- the reaction mechanism must agree with the experimentally determined rate law
108
What does "k" in the rate law represent?
indicates the speed of a reaction
- small k value = slow reaction
- large k value = fast reaction
109
What is an average and instantaneous rate?
- Average Rate – averages the change in [reactants] or [products] per unit of time over a given time interval (secant line)
- Instantaneous Rate is the rate of reaction at a particular point in time (tangent line)
- The rate of the reactant is expressed using a negative sign, whereas the rate of the product is expressed using a positive sign.
110
What are the ways reaction rates can be measured?
- collect gas from reaction and measure the volume and pressure changes as reaction occurs (faster reaction = greater change in pressure/volume)
- reactions involving ions have a greater conductivity (more ions formed = greater conductivity)
- reactants changing colour (colour intensity measured by spectrophotometer)
111
What are some factors affecting rate change?
Chemical nature of the reactants
Concentration of reactants
Temperature
Presence of a catalyst
Surface area
112
What is collision theory?
- For a reaction to occur the reactant particles must collide
- Only a certain fraction of the total collisions cause chemical change; these are called successful collisions
- correct orientation of reactants and sufficient collision energy/activation energy (Ea) needed
113
What is activation energy?
The minimum potential energy increase of a system required for molecules to react
- sufficient Ea needed to break existing bonds and form new bonds
114
What is transition state theory?
- used to explain what happens when molecules collide in a reaction
- It examines the change, from reactants to products
- The kinetic energy of reactants is transferred to potential energy (PE) as the reactants collide, due to the law of conservation of energy
- Transition state can be represented by a potential energy diagram (transition state is at the top of the hill)
115
what is the Maxwell-Boltzmann Distribution?
- The distribution of kinetic energy of entities
116
what are the Theoretical Effect of Chemical Nature of Reactant?
- The rate of any reaction partially depends on the chemical nature of the reactants
- Some molecules have bonds that are relatively weak and have small activation energy barriers which increases reaction rate
- can be colour changing
117
what are the Theoretical Effect of Concentration?
higher concentration of reactant = greater number of particles per unit volume = increase in likelihood of collisions = increased reaction rate
118
what are the Theoretic Effect of Temperature?
increased temperature causes molecules to collide both more often and with more force on average, making an individual collision more likely to be effective = increased reaction rate
119
what are the Theoretical Effect of Catalysts?
- Catalysts accelerate a reaction by providing an alternative lower energy pathway from reactants to products
- If the new pathway has a lower activation energy = a greater fraction of molecules possess the minimum required energy = reaction rate increases
- catalyst do Not increase # of collisions or increase kinetic energy of reactant entites
120
what are the Theoretical Effect of the Surface Area?
- reactants collide only at the surface where the substances are in contact
- Dissolving divides solid or liquid solute into the theoretical maximum number of separate particles, creating the maximum possible surface area. This is why so many reactions occur more quickly in solution
121
What is Standard Molar Enthalpy of Formation?
The quantity of heat energy released/absorbed when one mole of a compound is formed directly from its elements in their standard state (SATP)
122
What is an alternative equation for mass and moles?
- mass = density x volume
- moles = concentration x volume
123
What is a Dynamic equilibrium?
a balance between forward and reverse processes that are occurring simultaneously at equal rates (no observable change occurs)
124
What is Static equilibrium?
Irreversible reactions where reactants no longer turn into products
125
What is Chemical Equilibrium?
The state of a reaction in which all reactants and products have reached constant concentrations in a closed system
126
What is the Equilibrium position?
the relative concentrations of reactants and products in a dynamic system
127
What does the K value indicate in relation to 1?
- If K>1 🡪 The reaction proceeds towards completion. The concentration of the products is much higher than the concentration of reactants at equilibrium
- If K = 1 🡪 The concentrations of reactants and products are approximately equal at equilibrium
- If K<1 🡪 Very small amount of products are formed. The concentration of the reactants is much larger than the concentrations of products at equilibrium
128
Why are the concentrations of solids and liquids not included in the equilibrium expression law?
the concentrations of pure solids and liquids cannot change (are constant)
To simplify the equilibrium law equation, all constants are incorporated together with K
129
What is the quotient and what does its values mean?
- Q is used to figure out which direction the equilibrium will shift.
- If Q = K The system is at equilibrium
- If Q < K: The system will shift towards the products because not enough product has formed
- If Q > K: The system will shift towards the reactants because too much product has formed / passed equilibrium
130
What is the hundred rule?
divide initial concentration of reactants by k value
- if more than 100 then value can be ignored
- If less than 100 then the value cannot be ignored (% error is less than 5%)
131
What does it mean if K increase? decrease?
- Increase in K means equilibrium has shifted to the product side (right)
- Decrease in K means equilibrium has shifted to the reactant side (left)
132
What is molar solubility?
amount of material able to dissolve in 1 mol of solvent per litre to create a saturated solution
133
What is Ksp?
- equilibrium constant of a dynamic equilibrium between a solute and a solvent in a saturated solution (sparingly/slightly soluble salts)
- Dependant on temperature
134
What is the common ion and how does it reduce solubility?
A common ion is an ion that is present in two different solutes. Its presence decreases
the solubility of the less-soluble substance because it shifts the equilibrium toward the
solid (left because supersaturated).
135
What does a larger and smaller Ksp value mean?
- smaller Ksp = less soluble in water
- larger Ksp = more soluble in water
136
What is the reaction quotient used for?
predict whether a precipitate will form or not when solutions are mixed for slightly soluble salts
137
What is the relationship between Qsp and Ksp?
- Qsp > Ksp: supersaturated solution. Too much product has been formed. equilibrium shifts to the left and a precipitate is formed.
- Qsp = Ksp: Saturated solution at equilibrium, no precipitate forms and no more solid dissolves
- Qsp < Ksp: unsaturated solution. Not enough reactant has been converted to product. equilibrium will shift to the right, no precipitate forms and more solid can dissolve.
138
What is Le Chatelier's Principle?
When a chemical system at equilibrium is disrupted by a change in a property, the system adjusts in a way to oppose the change. A new equilibrium is established, in which concentrations are different from their original value.
139
What is an application of Le Chatelier's Principle?
Chemical engineers strive to design processes where reactants are continuously added and products are continuously removed, so that the equilibrium is never allowed to establish. If the reaction is always moving forward, the process is always making more products.
140
How does collision theory relate to concentration changes?
more reactant is added, the concentration of reactant molecules per unit volume increases, collisions are more frequent/successful for the forward reaction (rate increases)
141
How does temperature change relate to Le Chatelier’s Principle?
- the equilibrium shifts to minimize the temperature change
- If the system is cooled, the system tries to warm itself and the equilibrium shifts in the direction to produce more heat
- If heat is added, the equilibrium shifts in the direction that absorbs heat (cooling).
142
How does gas volume change relate to Le Chatelier’s Principle?
- total number of gas reactants and the total number of gas products need to be considered.
- Le Chatelier’s principle suggests that the system will react in way to resist the change by shifting to a side with more or less mols to change pressue
143
How does collision theory relate to gas volume changes?
When the volume of the reaction vessel decreases, the concentration of each gas in the mixture increases = more collisions occurring in the forward reaction
144
What changes do not affect the position of equilibrium?
- Adding catalyst: only decreases amount of time to reach equilibrium (lowers Ea for forward and reverse reactions) (NO OTHER AFFECTS)
- Adding inert gases: they are nonreactive (noble gases) only used to change pressure of system and redirect particle movement
145
What is solubility?
the amount of solute dissolved in a given amount of solvent to create a solution
146
What is Arrhenius Theory of Acids and Bases?
- When acids and bases dissolve in water, they dissociate into their ions
- acids dissociates to produce hydrogen ions
- base dissociates to produce hydroxide ions
147
What are some common strong acids and bases?
- Acids: HBr, HCl, H2SO4, HNO3, HI, HClO4
- Bases: Ca(OH)2, NaOH, LiOH, Mg(OH)2, KOH, Metal Oxides (e.g. MgO, K2O, BaO, etc)
148
What are some common weak acids and bases?
- Acids: H2CO3, HF, HClO2, H3PO4, HCN, HNO2, HCOOH, CH3COOH, LiCOOH
- Bases: NH3, N2H4, C2H5N, Organic amines & amides
149
What are some limitations of the Arrhenius Theory?
- H+ does not exist on its own in solution, it becomes hydrated and turns into H3O+ (hydronium ion)
- Not all bases contain hydroxide ions (ex. ammonia (NH3) and oxides of the alkali metals (Na2O)
150
What is Bronsted-Lowry Theory of Acids and Bases?
- An acid is a substance from which a proton (H+ ion) can be removed (“proton donor”)
- A base is a substance that can remove a proton (H+ ion) from an acid (“proton acceptor”)
151
What is a conjugate acid-base pair?
- molecules or ions related to one another by the transfer of a proton
- Conjugate-base of an acid is the species that remains when a proton is removed from the acid
- Conjugate-Acid of a base is the particle that forms when the base received the proton from the acid
*pairs are always found on opposite sides of the arrow
152
What is amphoteric?
A substance that acts as a Bronsted-Lowry acid in one reaction, and a Bronsted-Lowry base in a separate reaction
153
What are the key formulas?
pH = - log[H3O+(aq)]
[H3O+(aq)] = 10 – pH
pOH = - log[OH-(aq)]
[OH-(aq)] = 10 – pOH
pH + pOH = 14
Kw = [H3O+(aq)][OH-(aq)]
Ka x Kb = Kw (For an acid and it's conjugate base or vice versa)
154
How do salts containing group 1 and 2 cations affect pH?
- Salts that contain cations of group 1 or 2 (except for Be2+) of strong bases have no effect on pH
- The cations have no affinity for OH- ions (ie. they prefer to remain as ions in solution so they will not react with water)
155
How do salts containing anions of strong acids affect pH?
- Salts that consist of anions (like Cl- and NO3-) of strong acids have no effect on pH
- The anions have no affinity for H+ ions (ie. prefer to remain as ions)
156
How do salts containing cations that are conjugate acids of weak bases affect pH?
- Salts that consist of the cations (like NH4+ and N2H5+) that are conjugate acids of weak base form acidic solutions
- Salts that consist of certain metal cations (like Al3+, Fe3+, Sn2+) form acidic solutions
- Reacts with water to produce H30+
157
How are acidic salts formed?
Formed from the reaction between a strong acid and a weak base
158
How do salts containing anions of weak acids affect pH?
Salts that consist of anions (like CH3COO-) that are conjugate bases of weak acids form basic solutions
159
How are basic salts produced?
Formed from the reaction between a strong base and a weak acid
160
What is monoprotic, diprotic and triprotic acids?
- Monoprotic: acids only have one hydrogen ion
- Diprotic: acid has two hydrogen ions
- Triprotic: acid has three hydrogen ions
161
How are neutral salts formed?
Formed from the reaction between a strong acid and a strong base
162
How do metal and non-metal oxides affect pH?
- Metal Oxides: react with water to produce basic solutions. Example: MgO
- Non-metal oxides react with water to produce acidic solutions. Example: SO2(g)
163
How do strong and weak acids ionize in water?
- strong acids ionize completely in water
- weak acids ionize partially in water
164
What is percent ionization?
The percentage to which a weak acid/base ionizes is calculated as the percentage of [H3O+] or [OH-] that appears in solution once an equilibrium is established
165
What does the number for Kb value represent?
The smaller the Kb, the weaker the base
166
What is the relation between conjugate acids and conjugate bases with the reactants?
- The conjugate acid of a strong base is ALWAYS a weak acid
- The conjugate base of a strong acid is ALWAYS a weak base
167
What is the titration process?
A process used to determine the concentration of one solution by observing its reaction with a solution of known concentration (standard solution) until it reaches the equivalence point
168
What is an acid-base indicator, endpoint, Analyte and Titrant?
- Acid-base indicator: used to show when the equivalence point is reached (are weak acids but don't affect pH)
- Endpoint: point where the indicator changes colour
- Analyte: unknown concentration solution in the beaker
- Titrant: known concentration in the burette
169
What happens during the neutralization of a strong acid and strong base?
At the equivalence point, all of the H3O+ from the acid has reacted. The solution contains Na+ and Cl–, and neither of the ions reacts with water. The pH of the solution is due to the auto-ionization of water.
170
What happens during the neutralization of a strong acid and weak base?
The salt of a strong acid/weak base dissolves to form an acidic solution (pH < 7)
The ion from the salt which affects the pH forms an equilibrium with water
171
What happens during the neutralization of a weak acid and strong base?
- The salt of a weak acid/strong base dissolves to form a basic solution (pH > 7)
- The ion from the salt that affects pH forms an equilibrium with water
172
How do conjugate bases of strong acids affect pH?
Conjugate bases of strong acids are pH-neutral (they do NOT react with water).
173
How does the hundred rule relate to slightly soluble salts?
The Hundred rule is always valid for slightly soluble salts.
174
What is an easy way to predict if a salt solution is acidic, basic, or neutral?
If the ion comes from a strong acid or strong base → it is neutral.
If it comes from a weak acid or weak base → it affects pH.
12U Chemistry
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