General Chemistry 1 Flashcards
(121 cards)
1
Q
What is accuracy?
A
A measurement giving the Actual value for a sample with a limited deviation
2
Q
What is precision?
A
The repeatability of a set of measurements on the same sample
3
Q
Why is glass preferred in labs?
A
Inert, strength, transparency, heat resistant
4
Q
What are examples of calibrated glassware?
A
Graduated cylinder, graduated pipet, volumetric pipet , volumetric flask
5
Q
What does the shape of the meniscus tell you?
A
Meniscus is convex when the molecules of liquid are attracted to each other. Meniscus is concave when the liquid is attracted to the sides of the cylinder
6
Q
What is a pH meter?
A
Made of glass probe and electronic meter, uses difference in voltage to calculate PH, sample must be at known temperature
7
Q
How is litmus paper used?
A
Can be used to determine pH, paper is red under acidic conditions, paper is blue under basic conditions, paper is purple at neutral pH
8
Q
What are the two types of laboratory balances?
A
Standard laboratory balances and analytical balances (with sliding doors)
9
Q
What is calorimetry?
A
Way for chemist to measure energy content of a substance
10
Q
What are atoms composed of?
A
Subatomic particles; protons neutrons and electrons
11
Q
What are isotopes?
A
Atoms of the same element with different masses due to a different number of neutrons
12
Q
What are key points from Dalton’s hypothesis?
A
- All elements are made of very small particles called atoms (atoms of a given element are identical in size, mass and chemical properties)
- All compounds are composed of atoms of more than one element
- Chemical reactions involve only the separation, combination, or rearrangement of atoms, it does NOT result in the creation or destruction of atoms
13
Q
What is atomic number and what is atomic mass number?
A
Atomic mass number is total amount of protons and neutrons. Atomic number is total number of protons
14
Q
E=hf
A
E= energy value of a quantum h= Planck constant (6.626 x10^34 j .s) f = frequency of radiation
15
Q
L = NH/2 π
A
N= principal quantum number H= Planck constant L = angular momentum of an electron
16
Q
E=hc/λ
A
λ = wavelength of radiation
C= 3x 10^ 8 m/s
h=Planck constant
E= energy of electron
17
Q
What is an orbital?
A
A representation of the probability of finding an electron within a given region
18
Q
What is the Heisenberg uncertainty principle?
A
States that it is impossible to simultaneously determine an accurate momentum and the position of an electron
19
Q
What is the pauli exclusion principle?
A
No two electrons in a given atom can have the same set of 4 quantum numbers
20
Q
How do you calculate the maximum number of electrons in an electron shell?
A
2n^2
21
Q
What is the azimuthal/second quantum number?
A
Designated by the letter l, tells us shape of the orbitals and refers to the sub shells or sub levels that occur within each principal energy level, can range from 0 to n-1
22
Q
What sub shells do L= 0, 1, 2, 3 mean?
A
S, p, d and f subshells respectively
23
Q
How do you calculate the maximum number of electrons that can exist within a sub shell?
A
4L+2
24
Q
What is the magnetic/ third quantum number?
A
Designated with ml, this number describes the orientation of the orbital in space, possible values range from l to -l including 0
25
What is the fourth/spin quantum number?
Denoted by ms, has 2 spin orientations either 1/2 or -1/2
26
What is Aufbau’s Principle?
Subshells are filled from lowest to highest energy and each subshell will fill completely before electrons begin to enter the next one
27
What is Hund’s Rule?
In subshells that contain more than one orbital, orbitals are filled such that there is a maximum number of half filled orbitals with parallel spins
28
What does paramagnetic and diamagnetic refer to?
- If a material has unpaired electron, a magnetic field will align the spins of these electrons and weakly attract the atom to the field, and these materials are said to be paramagnetic
- Materials that have no unpaired electrons and are slightly repelled by a magnetic field are said to be diamagnetic
29
What is periodic law?
The chemical properties of the elements are dependent in systemic way upon their atomic numbers
30
What are A and B elements?
- The A elements are the representative elements which have either s or p sublevels as their outermost orbitals
- The B elements are the non representative elements including the transition elements and lanthanide and actinide series , which have partly filled d or f sublevels
31
What is effective nuclear charge (Zeff)?
The net positive charge from the nucleus, as felt by an electron
32
What are the periodic trends for Zeff?
Down a given column the outermost electrons become less tightly bound to the nucleus because the number of filled principal energy levels (which shield the outermost electrons from attraction by the nucleus) increases downward within each group
THEREFORE Zeff is at a max at the top right of the periodic table
33
What are the periodic trends for atomic radii?
Atomic radius decreases across a period from left to right and increases down a given group
From left to right across a period as electrons are added to the outer energy shell, the electrons get pulled closer to nuclear because Zeff increases as well
34
What are the trends for ionic radius for cations and anions?
- Usually cations (positive ions) will be smaller than the corresponding neutral atoms because they have fewer electrons and less repulsion among the remaining electrons
- Anions (negative ions) will be larger because more number of electrons and more repulsion
35
What is ionization energy?
- The energy required to completely remove an electron from a gaseous atom or ion
- The first ionization energy is the energy required to remove one valence electron and then the second ionization energy is the energy needed to remove a second valence electron
- Usually the second ionization energy is greater than the first unless the removal of the second electron would give it a fully filled or half filled valence shell
36
What are the periodic trends for ionization energy?
- Ionization energy increases from left to right across a period as Zeff increases
- Moving down a group, the ionization energy decreases as Zeff decreases
37
What is electron affinity and what are their trends?
- The energy change that occurs when an electron is added to a gaseous atom and it represents the ease in which the atom can accept an electron
- The higher the Zeff, the greater the electron affinity will be
- Positive electron affinity represents energy release when an electron is added to an atom OR negative electron affinity represents a release of energy ( FIRST USED MORE TIMES/COMMON)
- Group 2 (alkaline earth metals) have low electron affinity values because elements are relatively stable and s subshell is full
- Group 7 halogens have high electron affinities because the addition of an electron results in a completely filled shell
- Group 8 (noble gases) have electron affinities that are close to 0 because have full shells and cannot readily accept electrons
38
What is electronegativity?
A measure of the attraction an atom has for electrons in a chemical bond, the greater the atoms electronegativity the greater its attraction for bonding electrons
39
What is the periodic trend for electronegativity?
- Elements with low Zeff will have low electronegativities because their nuclei do not attract electrons strongly, while elements with a high Zeff wil have high electronegativity because of the strong pull the nucleus has on electrons
- Electronegativity increases from left to right across periods and decreases from top to bottom down a group
40
What are the types of elements?
Metals, nonmetals and metalloids
41
What are some properties of metals?
- Usually shiny solids, usually have high melting points and densities
- Can be deformed without breaking
- Malleable (can be hammered into shapes)
- Ductile (able to be drawn into wires)
- Good conductors of heat and electricity (few valence electrons)
- Large atomic radius, low ionization energy and low electronegativity
42
What are some properties of nonmetals?
- Poor conductors of heat and electricity
| - High ionization energies and electronegativities
43
What are some properties of metalloids?
- Densities, boiling points and melting points fluctuate
- Have characteristics of both metals and nonmetals since they lie in the middle
- Boron, silicon, germanium,. Arsenic, antimony, and tellurium are metalloids
44
What is a cation and what is an anion?
Cation is a positive ion and anion is a negative ion
45
What are the Alkali Metals and what are their properties?
- Elements of Group 1
- Physical properties common to metals but their densities lower than metals
- Have largest atomic radius
- Metallic properties and high reactivity due to their low ionization energies, easily lose their valence electron
- Low electronegativities and react readily with non metals
46
What are the Alkaline Earth Metals and what are their properties?
- Elements of group 2
- Commonly form +2 cations
- Have low electronegativities and positive electron affinities
47
What are some properties of the carbon group?
- Family containing carbon, group 4, has non metals, metals and -metalloids
- All have 2 electrons in their outermost p subshells
- Participates in electron sharing, tends not to form ions
- Usually most stable with 4 covalent bonds
48
What is the pnictogens and what are their properties?
- Nitrogen and the elements below it in group 5
- Often form 3 covalent bonds per atom
- Nitrogen usually has a positive charge in organic reactions
49
What are the chalcogens and what are their properties?
- Group 6 (oxygen group)
- Needs 2 valence electrons to complete their outermost shell
- Fairly electronegative to form -2 anions but can also participate in covalent bonds (preferring to have 2 shared electron pairs and 2 nonbonded pairs)
50
What are the halogens and what are their properties?
- Group 7
- Highly reactive nonmetals with 1 valence electron needed to fill outermost shell
- Commonly form -1 anions
- Variable in their physical properties: can be solid, liquid or gas
- Chemical properties: high electronegativities
51
What are the noble gases and what are their properties?
- Group 8, also called inert gases
- Non Reactive because they have a complete valence shell
- High ionization energies and no electronegativity
- Low boiling points and are gases at room temperature
52
What are the properties of transition elements?
- Groups 1B to 8B are all considered metals
- Very hard and have high melting and boiling points
- D electrons are held loosely by the nucleus and are relatively mobile which contributes to the malleability and conductivity
- Low ionization energies and can exist in variety of positively charged forms or oxidation states
- Can form many different ionic or partially ionic compounds
- Dissolved ions can form complex ions with either water (hydration complexes) or with nonmetals forming highly colored solutions and compounds
53
What are intramolecular and intermolecular bonds?
Bonds that hold atoms together as molecules and includes ionic and covalent bonds.
Intermolecular forces are weaker and between molecules
54
What is ionic bonding?
One or more electrons from an atom with a smaller ionization energy are transferred to an atom with a greater electron affinity and the resulting ions are held together by electrostatic forces
55
What is covalent bonding?
An electron pair is shared between 2 atoms
56
What is a polar covalent bond?
A bond that is partially covalent and partially ionic
Differences in electronegativity from 0.4-1.7, bonding pair pulled toward the element with the higher
57
What are properties of ionic and covalent compounds?
Ionic compounds have higher melting and boiling points and can conduct electricity in the liquid/aqueous state but not in solid state
Covalent compounds have weaker intermolecular forces, and lower melting points, and do not conduct electricity in liquid state
58
What is bond order?
The number of shared electron pairs between 2 atoms
59
What is bond length?
Bond length is the average distance between the two nuclei of the atoms involved in the bond; as the number of shared electron pairs increases, the 2 atoms are pulled closer together leading to a decrease in bond length
60
What is bond energy?
The energy required to separate 2 bonded atoms
61
How do you calculate formal charge?
valence electrons - (number of sticks +number of dots)
62
What are resonance structure?
2 or more non-identical lewis structures for same molecule but actual structure is a resonance hybrid
63
What is dipole moment and how do you measure it?
Dipole moment is a measure of the polarity of a molecule, vector quantity measured in debye units (coulomb meters) and is equal to charge times distance between 2 partial charges u=qr
64
What is a coordinate covalent bond?
The shared pair of electrons comes from the lone pair of one of the atoms in the molecule, typically found in lewis-acid base compounds
65
What is a Lewis acid and what is a Lewis base?
A lewis acid is a compound that can accept an electron pair to form a covalent bond
A lewis base is a compound that can donate an electron pair to form a covalent bond
66
What shape are s and p orbitals
Spheres and dumbbells
67
What is a bonding orbital and what is an anti bonding orbital?
- If 2 atomic orbitals are in phase with each other, a bonding orbital is formed
- If 2 atomic orbitals are completely out of phase with each other, an antibonding orbital is formed
68
What is a sigma bond?
When 2 orbitals of different atoms overlap, the resulting bond is called a sigma bond
69
What is a pi bond?
When parallel p orbitals interact a pi bond is formed
70
What are the intermolecular forces in order of highest to lowest strength?
Intermolecular forces: Dipole-ion interactions, hydrogen bonding, dipole-dipole interactions and london dispersion forces
71
What are considered the Vanderwaal Forces?
Dipole dipole and London dispersion forces
72
What is a compound?
Pure substance composed of two or more elements in a fixed proportion
73
What is a molecule?
A molecule is a combination of two or more atoms held together by covalent bonds and is the smallest unit of a compound that still displays the properties of that compound
74
What is the Laws of Constant Composition?
All samples of a given compound will contain the same elements in identical mass ratios
75
What is the empirical formula and what is the molecular formula?
- The empirical formula gives the simplest whole number ratio of the elements in the compound
- The molecular formula gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula
76
What is the limiting reagent and what is the excess reagent?
- Limiting reactant limits the amount of product that can be formed in the reaction and it will be consumed first
- The other reactant is the excess reactant
77
What is the theoretical yield and what is the actual yield?
- The theoretical yield is the amount of product that can be predicted from a balanced equation assuming that all of the limiting reactant has been used and no competing side reactions have occurred
- Actual yield is the amount of product isolated from the reaction experimentally
78
What is the rate determining step?
The slowest step in a proposed mechanism is called the rate determining step because the overall reaction cannot proceed faster than that step
79
What is chemical kinetics?
The study of the rates/or speed of reactions
80
What is the reaction rate and what are it’s units?
- The reaction rate is the change of concentration of reactant or finished product with respect to time
- Rate is expressed in the units of moles per liter per second (mol/LxS) or molarity per second
- Rate is positive for products being produced and negative for reactants being consumed
81
What is the rate constant?
The rate constant (k) is defined as a constant of proportionality between the chemical reaction rate and the concentration of the reactants
82
What is the order of the reaction and the reaction order?
- The exponents are called the orders of the reaction and they are equal to the stoichiometric coefficients of the rate determining step
- The overall order of a reaction (reaction order) is defined as the sum of the exponents
83
What is the collision theory of chemical kinetics?
Collision theory of chemical kinetics: states that rate of reaction is proportional to the number of collisions per second between the reacting molecules
84
What constitutes an effective collision?
An effective collision (one that leads to the formation of products) occurs only if the molecules collide with the correct orientation and sufficient force to break the existing bonds and form new ones
85
What is the activation energy?
The minimum energy of collision necessary for a reaction to take place is the activation energy or energy barrier
86
What is the transition state/activated complex?
Transition state: when molecules have effective collisions, old bonds are weakened and new bonds are beginning to form
The transition state (also called the activation complex) has greater energy than either the reactants or the products
87
What is enthalpy change?
- The enthalpy change of the reaction (delta H) is the difference between the potential energy of the products and the potential energy of the reactants
- A negative enthalpy change indicates an exothermic reaction (heat given off) while a positive enthalpy change indicates an endothermic reaction (where heat is absorbed)
88
What factors can affect reaction rate?
- The greater the concentrations of the reactants, the greater the number of effective collisions per time and the reaction rate will increase (except for zero order reactions)
- The reaction rate will increases as temperature increases, since it increases the average kinetic energy
- The medium a reaction takes place in can affect the rate of reaction, certain reactions proceed more rapidly in aqueous solution whereas other reactions proceed more rapidly in nonpolar solvents
- State of medium (solid, liquid or gas) can also have a significant effect
89
What are catalysts and what are some of the ways they work?
- Catalysts are substances that increase reaction rate without themselves being consumed, they lower the activation energy
- Catalysts may increase the frequency of collision between reactants, change orientation of reactants to have higher percentage of collisions, reduce intramolecular bonding with reactants etc
90
What are the types of catalysts?
A homogenous catalyst is a catalyst that is present in the same phase as the reactants. So for reactants that are in the gas phase, a homogenous catalyst is also a gas. A catalyst is heterogeneous if it is in a phase different from that of the reactants.
91
What are the types of systems and their properties?
Isolated: it cannot exchange energy or matter with the surroundings
Closed: It can exchange energy but not matter with the surroundings
Open: It can exchange both matter and energy with the surroundings
92
q=mc(deltaT)
Q is heat measured in calories or joules, m is mass, c is specific heat capacity and delta T is change in temperature
93
What is an isobaric process?
Process that occurs in systems at constant pressure, heat given off or absorbed is equal to the change in enthalpy of the system
94
What is an isochoric process?
Occur at constant volume, heat given off or absorbed equals the change in internal energy of the system and also equals that change in enthalpy of the system
95
What is an isothermal process?
Occurs when systems do not change temperatures, the change in internal energy as well as enthalpy is equal to 0 but heat does not equal 0
96
What is an adiabatic process?
Occurs when there is no heat exchanged between systems and their surroundings, change in internal energy is equal to work
97
What is bond dissociation energy?
The energy required to break a specific chemical bond in one mole of gaseous molecules
98
What is entropy and what is it’s units?
Entropy (s) is a measure of the disorder or randomness of a system and the units are energy/temperature which is J/K or cal/K
99
What is the 3rd law of thermodynamics?
The 3rd law of thermodynamics states that the entropy of a perfectly crystalline substance at 0K is 0
100
DELTAg= DELTAh- T(DeltaS)
Delta G= change in free energy of a system
T= absolute temperature in kelvin
Delta H= change in enthalpy
Delta s= change in entropy
101
What does the value of Keq tell you?
If Keq is larger than 1= more products and less reactants
If Keq is close to 1= equilibrium mixture and equal amounts of reactants and products
If Keq is less than 1= more reactants and less products
102
How do you compare Keq to Q?
If Q is less than Keq= greater concentration of reactants
If Q= Keq = reaction is in dynamic equilibrium and reactants and products are present in equilibrium proportions
If Q is greater than Keq = greater concentration of products
103
What is Le Chatelier’s Principle and what affects equilibrium?
- Le Chatelier's Principle: if an external stress is applied to a system at equilibrium, the system will attempt to adjust itself to partially offset the stress
- Changes in concentration
- Changes in pressure or volume (they are inversely related); when pressure increases the equilibrium will shift to the side with less moles
- Changes in temperature (also affects the value of Keq)
104
What is the common ion effect?
The quantity of a salt that can be dissolved is considerably reduced when it is dissolved in solution that already contains one of its ions rather than in a pure solvent-> reduction in solubility is called the common ion effect, wont change Ksp but will change molar solubility
105
What is a species?
A species is any group of similar organisms that are capable of producing fertile offspring
106
What is a population?
Population: group of organisms of the same species living in the same habitat
107
What is a biotic community and what is an ecosystem?
Biotic community is just the population while ecosystem includes the community and the environment
108
What is ecological succession? And what is primary and secondary succession?
- Ecological succession is the orderly process by which the structure of an ecological community evolves over time
- Primary succession occurs in area uninfluenced by a pre-existing community
- Secondary succession occurs in areas where a pre-existing community has been disrupted
109
What are pioneer organisms?
Pioneer Organisms: species able to colonize a barren area, allowing other organisms to follow
110
What is a climax community?
Climax community is the living (biotic) part of an ecosystem in which populations exist in balance with each other and with the environment
111
What is the criteria for a self sustaining and stable ecosystem?
- Abiotic factors and biotic community are relatively stable
- There is a constant energy source and a biotic community incorporating this energy into organic compounds
- Materials are cycled between the abiotic factors and biotic community
112
What are biomes?
Ecosystems within a specific geographic region form biomes
113
What are the types of terrestrial biomes?
Desert, grassland, rainforest, temperate deciduous forest, temperate coniferous forest, taiga, tundra and polar
114
What are characteristics of the desert biome?
Desert biome: minimal rain, inhabited by small plants and animals, plants conserve water, animals live in burrows, few birds and mammals except ones adapted
115
What are characteristics of the grassland biome?
Grassland Biome: low rainfall, no shelter for herbivore mammals from carnivorous predators, land animals present usually have long legs and hoofs
116
What are characteristics of the rainforest biome?
Rainforest biome: torrential rains, temperature is moderate, dense vegetation that doesn't shed its leaves, have vines and epiphytes (plants growing on other plants)
117
What are characteristics of the temperate deciduous forest biome?
Temperate deciduous forest biome: cold winters, warm summers, moderate rainfall, trees that shed leaves, animals like deers foxes and birds
118
What are characteristics of the temperate coniferous forest biome?
Temperate coniferous forest biome: Forests are cold, dry, more trees that don't shed leaves and conserve water, animals like beavers and bears and birds
119
What are characteristics of the taiga biome?
Taiga biome: Less rainfall than temperate forests, have long cold winters, have trees that do not shed, soil covered in moss, moose and deer found and some birds/rodents
120
What are characteristics of the tundra biome?
Tundra biome: Treeless, frozen plain, snow and ice (permafrost), short summer
121
What are characteristics of the polar biome?
Polar region: frozen with no vegetation, few terrestrial animals, little precipitation
