Chemistry exam Flashcards
1
Q
What are John Dalton’s Billiard Ball model 5 proposals? Draw it.
A
- All matter is composed of tiny, indivisible particles called atoms
- all atoms of an element have identical properties
- atoms of different elements have different properties
- atoms of two or more elements can combine in constant ratios to form new substances
- in chemical ractions, atoms join together or separate from each other but are not destroyed
created in 1807
2
Q
What are J.J. Tompson’s Plum Pudding Model 5 proposals
A
- atoms contain negatively charged electrons
- electrons are evenly distributed through the atom
- atoms are neutral, so there must be positive charges to balence out the negative charges
3
Q
What is rutherfords gold foil experiment
A
A piece of gold foil was hit with high speed alpha particles, which have a positive charge. All of the atom’s positive charge and most of the atom’s mass were concentrated at a tiny point in the centre (the nucleus). The electrons surrounded the nucleus and occupied most of the atom’s volume, but they only made up a small fraction of the atom’s total mass.
4
Q
What are Chadwicks neutrons?
A
Chadwick discovered that the nucleus contains neutral particles (neutrons) as well as positively charged particles (protons)
5
Q
What makes the atoms of one element different from the atoms of another element?
A
The number of protons in the nucleus!
6
Q
Are the number of electrons is equal to the number of protons
A
yes
7
Q
what are isotopes
A
two versions of a element, when an element has multiple masses
8
Q
What is average atomic mass?
A
Average atomic mass is the weighted average mass of all isotopes of an element found in nature, taking into account their relative abundances.
9
Q
ChatGPT
Average atomic mass is the weighted average mass of all isotopes of an element found in nature, taking into account their relative abundances.
A
Therefore the atomic mass of germanium is 72.7 u
10
Q
What is mass spectrometer? and How does it work?
A
identify isotopes and their respective abundances
the sample is vaporized (converted to the gas phase by heating)
An electron beam bombards the vapors, which converts the vapors to ions
Because mass spectroscopy measures the mass of charged particles, only ions will be detected, and neutral molecules will not be seen.
11
Q
The disintegration of unstable isotopes is called…
A
radioactive decay
12
Q
Some isotopes are unstable and emit…?
A
nuclear radiation
13
Q
What are three types of nuclear radiation?
A
Alpha (α) particles: positively charged particles with the same structure as the nucleus of a helium atom
Beta (β) particles: negatively charged particles identical to electrons
Gamma (γ) rays: a form of high energy electromagnetic radiation
14
Q
What are radioisotopes
A
Isotopes that decay to produce nuclear radiation
15
Q
How to calculate electrons and neutrons?
A
Mass number = protons + neutrons
electrons = protons
16
Q
All elements in a column (group) have the same number of
energy levels or valence electrons
A
valence electrons
16
Q
All elements in a row (period) have the same number of…
energy levels or valence electrions
A
energy levels
17
Q
does the number of energy levels stay the same in a group or period
A
period
18
Q
What are sheilding electrons?
A
The electrons in the energy levels between the nucleus and the valence electrons
19
Q
How many sheilding electrons are in fluorine?
A
shielding electrons
20
Q
What is the trend of sheilding slectrons
A
The # of shielding electrons stays the same within a period (except for increasing gradually and erratically across transition metals)
21
Q
Does the number of valence electrons stay the same in a group or a period?
A
group
22
Q
What is ENC
A
Effective nuclear charge: The charge felt by the valence electrons after you have taken into account the number of shielding electrons that surround the nucleus.
23
Q
What is the ENC trend
in a group and period
A
Left-to-right in a period:
The number of protons increase, but the number of shielding electrons stays the same, thus the effective nuclear charge felt by the valence electrons increases
Top-to-bottom in a group:
As you go down a group, the increase in the nuclear charge is cancelled out by the increase in shielding electrons and the effective nuclear charge stays the same
24
What is the atomic radius?
Atomic radius of an atom is the distance from the nucleus to just beyond the outermost electrons (valence electrons)
25
Atomic radius trend and explaination (group and period)
Left-to-right in a period:
More protons in the nucleus for same number of energy levels = the ENC increases, stronger attraction between nucleus and electrons = smaller atomic radius
Top-to-bottom in a group:
Number of energy levels increases = weaker attractive force due to increasing number of shielding electrons = larger atomic radius
26
What is the ionic radius
Size of atom after ion formation depends on whether a cation (+) or anion (-) was formed
27
Ionic radius trend (cation and anion)
Cations are always smaller than their original neutral atoms
Anions are always bigger than their original neutral atoms
28
What is ionization energy
Ionization energy is the amount of energy required to remove an electron from an atom or ion in the gaseous state
29
ionization energy trend (period and group)
Ionization energies increase left-to-right across a period
ENC increases, so valence electrons are more strongly attracted to the nucleus, and thus more energy is required to remove an electron from the atom
Ionization energies decrease top-to-bottom in a group
Atomic radius increases, so the attraction between the valence electrons and nucleus becomes weaker, and thus less energy is required to remove the first valence electron
30
Electron affinity
Electron affinity is the energy change that occurs when an electron is accepted by an atom in the gaseous state
When an electron is added to a neutral atom in the gaseous state, energy is usually released
You can think of electron affinity as the amount of energy an atom (or ion) is willing to pay to buy another electron
31
electron affinity trend (group and period)
Electron affinity decreases top-to-bottom in a group
Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron
Electron affinity increases left-to-right across a period
ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron (noble gases are the exception)
32
electronegativity
describes the ability of an atom to attract electrons when bonded, combining ionization energies, electron affinity, and some other measures of reactivity
33
electronegativity trend (period and group)
Electronegativity generally decreases top-to-bottom in a group
Electronegativity increases left-to-right across a period
34
Metallic Reactivity trend
Reactivity increases top-to-bottom in a group
ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 allows metals to readily give up electrons
Reactivity decreases left-to-right in a period
ENC increases, electrons are added to same shell and held tightly = more difficult for metals to give away electron
35
Non metallic reactivity
Reactivity decreases top-to-bottom in a group
ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 harder for non-metals to gain an electron
Reactivity increases left-to-right in a period
ENC increases, electrons are added to same shell and since electronegativity increases across a period, non-metals will react to gain electrons
36
when are atoms the most stable
Atoms are most stable when the have a FULL valence energy level
37
what is an ion
when an atom gains or loses an electrion
37
Draw a lewis dot diagram for chlorine
38
Draw a lewis dot diagram for sodium
39
draw an ionic compound for sodium and chlorine
40
what is an ionic bond
the electrostatic force of attraction between a positive ion and a negative ion
41
what are the 4 physical properties of ionic compounds
Ionic compounds have relatively high melting points because their ions are held together by strong electrostatic forces (ionic bonds)
Ionic compounds are hard, but brittle. Held together by the attraction of oppositely charged ions (electrostatic forces)
Resistant to being stretched or compressed
Dissolve in water. When an ionic crystal is placed in water, water molecules surround each ion and separate it from the crystal
high conductivity of electricity. When an ionic compound is dissolved in water (ie. it’s aqueous form), the result is an electrolyte
The dissolved ions are able to move freely, and thus to carry electric charges, through the water
42
What is the structure of ionic compounds
The ions in an ionic compound are locked in a regular structure called a crystal lattice
43
What are all the diatomic molecules
HOFBrINCl
43
what are lone pairs
Non-bonded pair of electrons
44
Draw a lewis dot structure of cluorine compound
45
5 properties of molecluar compounds
State at room temp: Solid, liquid, or gas
Physical properties: Solids can be soft, waxy, flexible, or crystalline
boiling/melting point: Lower than ionic
solubility in water: Some good, some poor
electrical conductivity: Low or none
45
What are the rules for drawing lewis structures
Rule 1: The central atom is usually the least electronegative atom (or largest bonding capacity)
Rule 2: Other atoms surround the least electronegative atom
Rule 3: Count the total number of valence electrons, including charges
Rule 4: Place electron pairs between each atom to represent a single covalent bond, then distribute the remainder of the electrons around the surrounding atoms (except hydrogen) to satisfy octet rule.
Rule 5: Replace electrons with lines to represent bonds and place square brackets around the final structure. Indicate the charge on the structure by placing the charge on the outside of the right square bracket.
45
What is a structural formula
lewis dot without lone pairs
46
Draw lewis dot for CH2O
47
calculate electronegativity for sodium and fluorine
ΔEN = 4.0 – 0.9
ΔEN = 3.1
48
How do you use EN to find the type of chemical bond
0-0.4 (nonpolar covalent)
0.41-1.69 (polar covalent)
1.7 (ionic)
49
what is polar covalent bond and non-polar covalent?
polar covalent bond: unequal sharing of electrons
non-polar covalent bond: equal sharing of electrons
50
what is a polar molecule?
A polar molecule is slightly positively charged at one end and slightly negatively charged at the other because of electronegativity differences
51
draw convention for HCl
52
Draw convention for water
53
what happens when a molecule is symmetrical
it lacks oppositely charged ends and so is NOT polar.
54
when do you use bent shape
2 bonding pairs (central atom)
2 lone pairs (central atom)
Polar molecule (if polar covalent bonds)
55
draw convention for carbon tetrachloride
56
when do you use trigonal pyramidal shape
3 bonding pairs
1 lone pair
Polar molecule
(if polar covalent bonds)
57
when do you use Linear Shape
2 bonding pairs
no lone pairs
Non-polar molecule
58
when do you use trigonal planar
3 bonding pairs
no lone pairs
Non-polar molecule
59
when do you use tetrahedral shape
4 bonding pairs
no lone pairs
Non-polar molecule
60
What are instramolecular forces
are forces which physically keep substances together (e.g., ionic and molecular bonds)
61
What are intermolecular forces
An intermolecular force is an attraction between molecules
62
how are ionic compounds held together
Ionic crystals are held together by electrostatic ionic bonds, which are much stronger than intermolecular forces
63
how does The strength of intermolecular forces determines physical properties of molecular compounds
As the intermolecular forces between molecules in a molecular compound increase, the compound’s melting point, boiling point, and surface tension also increase.
64
what are dipole-dipole forces
An intermolecular attraction between opposite partial charges of polar molecules; a hydrogen bond is a particularly strong version of a dipole-dipole force (polar molcules)
65
what are ion-dipole forces
An intermolecular attraction between partial charges of polar molecules and ions (polar and ions)
66
what are London Dispersion Force
A weak intermolecular attraction between all entities, including non-polar molecules and neutral atoms, due to temporary dipoles (all entities other than ionic crystals)
67
What is a special dipole-dipole force?
A dipole-dipole force is classified as a hydrogen bond if at least one of the dipoles involved arises from an H-F, H-O, or H-N bond (FON)
these bonds are much stronger than regualr dipole-dipole forces
68
why does the stronger intermolecular force = the higher its melting/boiling point
Why?
In liquids and (to a greater extent) gases, entities are able to freely move past one another
To achieve this, entities must have sufficient kinetic energy (as measured by its temperature) to overcome its intermolecular forces
For entities with strong intermolecular forces, this sufficient level of kinetic energy is higher – that is, they melt and boil at higher temperatures
69
What happens when water freezes
the molecules lose kinetic energy, and slow down
Hydrogen bonds start to arrange the molecules into a crystalline structure
This arrangement contains more space between the molecules than does the more random arrangement of liquid water molecules
70
why does water have high suface tension
The hydrogen bonds in water cause water molecules to hold strongly to each other, pulling together and resisting being broken apart.
This causes water to take a shape that has the smallest possible surface area, forming beads or droplets.
Other liquids don’t do this!
71
How to name ionic compounds
First part of the name comes from the cation
If cation is multivalent, must indicate charge after the name in brackets using Roman Numerals
Second part comes from the anion
If the anion is an element, its name is modified to end in –ide
If the anion is polyatomic, must determine correct name
72
How do you name polyatomic ions
x+1 (per____ate)
x (_____ate)
x-1 (____ite)
x-2 (hypo____ite)
73
How do you name hydrates?
regular name of compound and then amount of water molecules has a prefix
ex. nickel (II) chloride hexahydrate
74
What is a hydrate?
A hydrate is an ionic compound that includes water molecules within its crystal structure
75
How do you name molecular compounds?
both elements need prefixes of (mono, di etc.)
last element needs a suffix of -ide
76
Why are acids unique
they act like molecular compounds until theyre dissolved in water, when dissolved they break apart into ions like an ionic compound
77
What are binary acids and how do we name them
if the formula of the acid does not includ oxygen
prefix: hydro-
suffix: -ic
then end with acid
78
What is an oxyacid and how do we name them?
when the formula does indxlude oxygen (polyatomics)
x+1: per___ic acid
x: ___ic acid
x-1:___ous acid
x-2: hypo___ous acid
79
What is the name of H2CrO5
perchromic acid
80
what are some indicators of a chemical reaction?
Change in colour
Energy is released or absorbed
A gas is produced
A precipitate forms
81
What is the law of conservation of mass
during a chemical reaction, the total mass of reactants equals the total mass of products
82
What is a complete combustion reaction and its products
The complete combustion of a hydrocarbon occurs when the oxygen supply is plentiful.
Complete combustion is the ideal way to burn a fuel because it releases the most energy from the fuel molecules
As a result, complete combustion produces the cleanest (least sooty) and hottest flames (blue)
always produces
CO2(g)+H2O(g)+energy
83
What is incomplete combusion and products
Incomplete combustion of hydrocarbons occurs when the supply of oxygen is limited
always produces
c(s)+CO(g)+(CO2(g)+H2O(g)+energy
84
complete combustion and incomplete for heptane
85
What are the concerns relating to incomplete combustion
1. Incomplete combustion releases only a portion of the energy that may be obtained from hydrocarbon fuels!
2. Soot particles from incomplete combustion are an inhalation hazard. Many of the chemicals in soot are toxic.
3.Carbon monoxide produced during incomplete combustion is also an inhalation hazard – the “silent killer”
86
what are the 5 types of synthesis reactions
1) Metal/Non-metal + Oxygen
2) Metal + Non-Metal
3) Metal Oxide + Water
4) Non-Metal Oxide + Water
5) Non-Metal Oxide + Metal Oxide
87
complete the reactions for CaO + H2O
88
how can acid rain and ocean acidification occur
through synthesis reaction of a non-metal oxide and water
89
what is an acidic oxide
An oxide that forms an acidic solution when dissolved in water; a non-metallic oxide
89
how do you conteract the effects of acid rain
by adding a metal oxide to lakes to produce synthesis reaction of a base, which reacts with the acid to produce water
90
what is a basic oxide
An oxide that forms a basic solution when dissolved in water; a metallic oxide
91
what are 3 examples of indirect gas productoin
H2SO3(aq)->H2O(l)+SO2(g)
H2CO(aq)->H2O+CO2
NH4OH(aq)->NH3(g)+H2)(l)
92
what is avogadro's constants number
NA = 6.022x10^23
93
calculate atoms of lithium knowing 3 moles of Li
94
calcualte molar mass
sum of the molar masses of all entities
95
formula for mass given moles and molar mass
m=nM
96
According to the manufacturer, a typical can of cola contains 40.0 g of sucrose (C12H22O11). Calculate the amount of sucrose in 40.0 g.
97
Octane, C8H18, is a principal ingredient of gasoline. Calculate the mass (in kilograms) of 1.78x102 mol of a sample of octane.
98
How do you calculate number of entities
N=nNA
99
A sample contains 1.25 mol of nitrogen dioxide, NO2.
How many molecules are in the sample?
100
Calculate the number of molecules in a 4.00 mg sample of ammonia, NH3.
101
Find the number of carbon, hydrogen, and oxygen atoms in a 26.5 g sample of benzaldehyde, C6H5CHO.
102
what is the formula for mass percent
mass percent of element A = mass of element A/mass of compound AB x 100%
103
The tablet weighs 500.00 mg, and it’s chemical formula is C9H8O4
The carbon atoms make up 300.00 mg of the tablet
The hydrogen atoms make up 8.08 mg of the tablet
The oxygen atoms make up the remaining mass
104
Law of Definite Proportions
A compound always contains the same proportion of elements by mass
105
Determine the percentage composition of sodium sulfate, Na2SO4.
106
what is the empirical formula
An empirical formula shows the simplest whole-number ratio of elements in a compound
107
what is teh molecular formula
A molecular formula shows the exact number of each type of atom in a molecular compound
108
Determine the empirical formula of a compound that contains 50.85% carbon, 8.47% hydrogen, and 40.68% oxygen.
109
The formula for hydrated magnesium sulphate is MgSO4 ∙ x H2O, where x represents the number of moles of water per mole of MgSO4. 8.86g of this hydrate is heated and all of the water is lost, leaving 4.33g of MgSO4 remaining.
a) Calculate the percent, by mass, of water in MgSO4 ∙ x H2O [1 decimal value]
b) Find the value of x in MgSO4 ∙ x H2O
110
Consider the following reaction:
P4(s) + 5 O2(g) 🡪 2 P2O5(g)
What amount of oxygen is required to produce 0.250 mol of the product?
111
what is stoichiometirc amount
A stoichiometric amount is an amount of reactants that is in the same proportion as the reactant coefficients in the balanced chemical equation
112
4 NH3(g) + 5 O2(g) 🡪 4 NO(g) + 6 H2O(g)
Determine the limiting reagent if 0.34 g of NH3 combines with 1.00 g of O2.
113
what are the 4 steps to solving a stoichiometry problem
1. Convert masses to moles
2. find limiting
3. use moles of limiting to find moles of product
4. convert moles of product to mass of product
114
theoretical yield
is the mass of product predicted based on the stoichiometry of the chemical equation
115
actual yield
is the mass of product actually collected during an experiment or industrial process
116
what are some reasons why actual yield in less than theoretical yield
Reaction reversibility (Some reactions have a competing reverse reaction)
The experimental procedure (Regardless of how careful chemists are, they inevitably lose small quantities of material in most investigations!)
Impurities
Competing side reactions (competing reactions prevent some of the reactants from being converted into products)
117
percentage yield
numerical value of Comparing the actual yield in a reaction to the theoretical yield gives an indication of how efficient or successful the reaction is at converting reactants into products
percentage yield = actual yield/theoretical yield x 100
118
Using the given masses of reactants, we calculate that 106 g of CH3OH should be produced in this reaction. However, when we go do the reaction, we measure only 102 g of CH3OH product. What is the percentage yield of the reaction?
119
what is percent error? and its formula
Percent error is the difference between the experimental value and the theoretical value, as a percentage of the theoretical value
120
what is hydration
As the ions leave the crystal form, they become surrounded by a sphere of water molecules
121
what is dissociation
The process in which ions separate from ionic crystals, becoming individual ions, is called dissociation
122
describe like dissolves like
Solutes dissolve in solvents of similar polarity
molecular compounds must be polar to dissolve in water (due to hydrogen bonding)
non-polar molecules cna dissolve in non-polar solvants (due to londan dispersion forces)
123
what are surfactants
These are special molecules that encourage polar and non-polar molecules to mix
They have both a polar and a non-polar part
124
formula for amount concentration
c=n/V (in L)
125
what is a solvant
The substance doing the dissolving
125
what is a solute
The substance being dissolved
126
saturated solution
A solution that contains the maximum quantity of solute, otherwise known as its solubility
127
how do you make a supersaturated solution
A super saturated solution is prepared by dissolving the solute in water at a high temperature, then allowing the solution to cool
As the temperature drops, the solubility drops, but the extra solute doesn’t crystalize from the solution immediately – the solution becomes supersaturated
The extra solute stays dissolved until something disturbs the system
A tap on the flask or dropping a single crystal of solute into the solution can initiate crystallization!
The “seed crystal” provides a surface onto which excess solute can crystallize
127
unsaturated solution
A solution that contains less than the maximum quantity of solute
127
supersaturated
under special circumstances, you can force a solution to dissolve more solute than it normally would
128
why do soft drinks bubble and fizz when theyre opened
The solubility of a gas in a liquid increases as the pressure of the gas is increased
When you open the can/bottle, the pressure drops, so the CO2 comes out of solution, which results in bubbling/fizzing
129
how to calculate percent concentration
1. percentage v/v
c=v/v x100
2. C=w/v=m/v
3.c=m/mx100
130
A 250 mL sample of tap water is found to contain 12 ppb of an antibiotic. Determine the mass of the antibiotic in the sample.
130
whats does pp mean
"parts per"
131
standard solution
solution for which the precise concentration is known
132
Suppose you want to prepare a standard copper (II) sulfate aqueous solution with a concentration of 1.0 mol/L, and you have a 200.0 mL volumetric flask. What mass of copper (II) sulfate do you need?
133
net ionic equation
ionic equation iwhtout spectator ions
134
total ionic equation
balenced chemical equation
134
dilution calculations
c1V1=c2V2
135
Arrhenius Theory of Acids & Bases
An ACID is a molecular compound that ionizes to produce hydrogen ions in water
A BASE is an ionic compound that dissociates to produce hydroxide ions in water
136
ionization
The formation of new ions from an uncharged molecule
137
how much does one pH unit represent
one pH unit represents a tenfold change in the acidity or basicity of a solution!
138
how to determine the stretngth of an acid
Strong acids completely ionize in water, weak acids partially ionize in water
138
dissociation
The separation of ions that already exist in a neutral compound
139
equivalence point
Where neutralization is completed
moles of base = moles of acid
140
titrant
known concentration
140
analyte
unknown concentration
141
endpoint
point during a titration when there is a sudden change in colour of the acid-base indicator
142
Several 10.00 mL samples of sulfuric acid solution of unknown concentration are titrated with a 0.100 mol/L solution of sodium hydroxide. Use the data in the table below from a titration to determine the amount concentration of the acid solution.
v=12.46667mL
143
Kinetic molecular theory
describes how indivdual entities move
states that entities are capable of virbrational, rotational, and translational motion
144
how does temperature affect kinetic energy
as temperature rises, entities move more rapidly (faster they move greater kinetic energy)
145
Termperature
measure of the average kinetic energy of te entities in a subtance
146
kelvin
termperaure units (t+273.15)
147
how does the kinetic energy of gases also contributes to the pressure they exert
when kinetic energy or temp., in increased, entities hit walls more frequently. this results in greater force per unit area
147
how does a solid become liquid and liquid become gas
A solid becomes a liquid when there is sufficient kinetic energy to overcome some of the attractive forces between the entities, allowing the entities to flow past each other
Similarly, a liquid becomes a gas when the kinetic energy further increases to the point where all the remaining attractive forces are overcome
148
what is Gay-Lussac's Law
temperature increases, pressure increased proportionally, when volume and amount of gas remains constant (linear graph)
148
how does volume affect pressure
with a fixed temperature and entities, and volume decreases, pressure increases. this results in entities hitting the walls more frequently
149
Boyles law
reciprocal relationship
states that a gas's pressure and volume are inversely proporational
149
Charles Law
As the temperature of a gas is increased, the volume of the gas increases proportionally, provided that the pressure and amount of gas remain constant
linear
150
What are the cahracterisitics of an ideal gas?
1. Its entities all have high translational energy, moving randomly in all directions in straight lines
2. When its entities collide with each other or with the container walls, the collisions are perfectly elastic (no loss in kinetic energy)
3. The volume of an ideal gas entity is insignificant (zero) compared to the volume of the container
4. There are no attractive or repulsive forces between ideal gas entities
5. Ideal gases do not condense into liquids when cooled
151
Can we always use Ideal Gas Law?
Gases behave most ideally at low pressures and high temperatures
When the pressure gets too high, attractive forces between entities become significant (can’t have those for an ideal gas!)
When the temperature gets too low, the entities move too slowly and again attractive forces become significant
So we need to be careful about using ideal gas law at high pressures and/or low temperatures
152
Dalton’s Law of Partial Pressures
The total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases: P(total)=P+P+P+P
153
Collecting gas over water
in the lab, if a gas is produced in a reaction, we often collect it by bubbling it through water
The problem with this is that water vapour gets mixed in with our gas product (P(total)-Pwater=P
