chemistry fundamentals Flashcards
What unit of volume is used for laboratory work? Why?
Litres, because, the cubic meter, the SI unit for volume is too large for most lab work
1 L = ? cubic meter
1000
Define Molarity
Moles of solute per litre of solution
1mL = 1 cm3, True or False?
True
Litre is used to express the volume of solids? T/F
False, litre is used to express the volumes of liquid and gases
Define Angstrom?
Angstrom is a unit of length equals to 10^-10m. The atomic radii and bond lengths are typically around 1 to 3 A
Define Density? What are its SI units?
It is mass per volume. m/V. The SI Units of Density is kilogram per cubic meter (kg/m^3)
What is density most often expressed in?
Grams per cubic centimeter
What is the density of water?
1 g/cm3
Define Molecule
When two or more atoms form a covalent bond they create a molecule
How do we know the identity of a compound and the number of its atoms?
Using the molecular formula
Are molecular formula and empirical formula the same thing?
No, to get the empirical formula divide all subscripts by a common factor. Empirical formula is a reduced form of the molecular formula
What is the formula for ammonium?
NH 4 +
Identify H3O+
Hydronium
Formula for acetate?
CH3CO2-
IDENTIFY HCO3-
bicarbonate
FORMULA FOR CYANIDE
CN-
IDENTIFY OH-
HYDROXIDE
FORMULA FOR NITRATE
NO 3 -
FORMULA FOR NITRIDE
NO2-
IDENTIFY CL04-
PERCHLORATE
FORMULA FOR CARBONATE
CO3 2-
IDENTIFY SO4 2-
SULFATE
IDENTIFY SO4 2-
SULFATE
IDENTIFY SO3 2-
SULFITE
FORMULA FOR PHOSPHATE
PO 4 2-
Define formula weight? What is the unit?
Sum of all the atomic weights of all the atom in the molecule. The unit is atomic mass unit (amu). It says weight but it really is mass
Define one amu?
is equal to exactly 1/12 the mass of an atom of carbon -12
What is mole?
it is a particular number of things. One mole contains 6.02 x 10 ^23 entities (Avogadro’s number)
What is Avogadro’s number denoted by?
N A in the subscript or N 0 in the subscript
What is the link between atomic mass unit and grams?
Avogadro’s number
What is the formula to calculate number of moles?
mass in grams/ molecular weight
What formula is preferred to calculate percent mass composition?
Empirical formula
What expresses the concentration of a solution in terms of moles of solute per volume?
Molarity
[ ] = concentration? T/F
True
What is Mole fraction?
Fraction of moles of a given substance relative to the total moles in the solution
When is it more useful to use mole fraction over molarity?
Mole fraction is used when more than one solute is present in a solution and is often used in gases
What is the Law of conservation of mass?
the amount of mass does not change in a chemical reaction
Define stoichiometry co-efficients?
they tell us in what proportions the reactants react and products are formed
The stoichiometric co-efficients are used to give the ratios by mass. T/F
False, they give ratios of the number of molecules or moles
What is a limiting reagent?
Whatever reactant runs out first to limit the production of a product is called limiting reagent
Is limiting reagent a reactant that is present in the smallest amount? T/F
No, Limiting reagent is the reactant that is consumed first and not necessarily the reactant that’s initially present in the smallest amount.
A product can be a limiting reagent? T/F
False, only the reactants are limiting reagent.
What are the four states used in chemical formula?
Solid, liquid, gas and aqueous
Define catalyst.
A substance that increases the rate of reaction without being consumed
What does the oxidation state of an atom indicate?
Atom’s oxidation state or number indicates how the atom’s ownership of its valence electrons changes when it forms a compound.
What results in a positive vs negative oxidation state?
Giving up the ownership of valence electrons results in positive oxidation and accepting ownership of valence electrons results in a negative oxidation state.
What is the oxidation state of any element in its standard state?
0
What is the rule for oxidation state of an atom in a molecule/ion?
The sum of the oxidation state of the atoms in a neutral molecule must always be 0. For ions, the sum of the oxidation states of the atoms must always equal to the ion’s charge
What is the oxidation state of Group 1 and Group 2 metals?
+1 for Group 1 and +2 for group 2
Oxidative state of Flourine?
-1
What are the rules for oxidation state of hydrogen
+1 when bonded to something that is more electronegative than carbon, -1 when bonded to something less electronegative than carbon and 0 when it is bonded to carbon
What is the oxidative state of oxygen and atoms that belong to the oxygen family?
-2
What oxidative state do halogens have?
-1
When does O2 not have a oxidative state of -2?
In peroxides, oxygen is in a -1 oxidative state.
What is the pneumonic for the order of electronegativity?
FONClBrISCH (Fawn-cull-brish), most to least
In FONClBrISCH, identify the oxidative states of H.
Anything before C is +1 for H, anything that is not here is -1 for H.
A metal will never assume a negative oxidation state? T/F
True
What is an atom? What are some parts of the atom?
The smallest unit of any element is called an atom. All atoms contain a nucleus and outside the nucleus, there are electrons.
What is inside a nucleus?
Protons and nuetrons
What are nucleons?
Protons and neutrons are collectively known as nucleons
Charge of protons
+1
Charge of nucleus
0
charge of electrons
-1
How are electrons held inside an atom?
Through the electrostatic attraction of positively charged nucleus
every neutral atom has equal charge of electrons outside the atom and protons inside the atom? T/F
True
What is atomic number (Z)?
The number of protons in a nucleus of an atom
Are protons represented by a subscript or a superscript?
Subscript
What is the mass of protons and neutrons?
1.66 x 10 ^-27
What is the mass of an electron?
0.05 % mass of the protons or the neutrons
What contributes to all the mass of an atom
Nucleus
How do you find the mass number of an atom? (A)
of protons + # of neutrons
What are isotopes?
Two atoms of same element differ in their number of neutrons. (Protons stay the same)
What is an atomic weight of an element?
weighted average of all the masses of its naturally occurring isotopes
Define ions, anions, cations?
When a neutral atom gains or loses electrons, it becomes charged and the resulting atom is called an ion. A negatively charged atom is called anions. A positively charged atom is called cation.
Charge of an atom when it gains an electron
-1
Charge of an atom when it loses an electron
+1
How are neutrons and protons held together?
by strong nuclear force
Electrical force is stronger than nuclear force? T/F
False, nuclear force is stronger than electrical force between charged particles.
What is the limitation of the nuclear force?
It only works over extremely short distances
What is a radioactive nuclie?
An unstable nuclie
Define radioactive decay?
unstable nuclei undergo a transformation to make them more stable, altering the number and ratio of protons and neutrons or lowering their energy,
Difference between a parent nucleus versus the daughter?
The nucleus that undergoes the radioactive decay is known as the parent and the resulting more stable nucleus is known as the daughter
3 types of radioactive decay?
Alpha, Beta and gamma
Define alpha decay
When a large nucleus wants to become more stable by reducing the number of proton and neutrons by emitting an alpha particle.
What is the symbol for an alpha particle and what does it consist of?
α (4 superscript and 2 subscript). It consists of 2 protons and 2 neutrons
What atom is the alpha particle similar to?
Helium
Alpha decay reduces the parent’s atomic number by —- and mass number by —-
2 and 4
What particles cant travel very far and can be stopped by human skin and piece of paper?
Alpha Particles
What is beta decay?
Beta decay involved conversion of neutrons into protons or vice versa through the action of the weak nuclear force.
3 types of beta decay?
β− decay, β+ decay and electron capture
What type of particles can be stopped by aluminium foil and a centimetre of glass and plastic
Beta particles
Explain β− decay
β− decay is when an unstable nucleus contains too many neutrons, it may convert those into a proton and an electron which is ejected. As a result the atomic number of the daughter nucleus is 1 greater than the parent and the mass stays the same. (coverts into proton and electron, -ve and +ve = neutral,)
Explain β+ decay.
When an unstable nucleus contains too few neutrons, it converts a proton into a neutron and a positron is ejected. The atomic number of the daughter nucleus is one less than the parent nucleus but the mass stays the same. (protons gets converted into neutron that is neural, the leftover positive charge is emitted in a form of a positron)
Difference between an electron and positron?
Positron is antiparticle of electron. It is identical to an electron but has a positive charge.
What is the most common type of Beta decay?
β- decay.
Explain electron capture
An unstable nucleus increases its number of neutrons by capturing an electron from the closest shell (n=1) which is then used in the conversion of protons into neutrons ( -ve charge from electrons and +ve from protons = neutral neurones). The atomic number is reduced by 1 and mass stays the same.
Explain gamma decay
After the nucleus has undergone alpha or beta decay, it is in an excited state of energy. It can relax to its ground state by emitting energy in the form of one or more photons of electromagnetic radiation. This radiation changes neither the atomic number nor the mass number
What are the characteristics of gamma photons?
They have very high frequency and energy . They do not have mass or charge so they can penetrate most matter effectively.
Order in terms of least to highest degree of penetration, beta, alpha and gamma
Alpha < beta < gamma
True or False, alpha, beta and gamma decay change the identity of the nucleus
False, gamma doesn’t change the identity. Gamma decay is simply the expulsion of energy
Define half-life
Time it takes for one-half of some sample of the substance of decay.
True or False. Shorter the half life, the faster the decay?
True
What is nuclear binding energy?
The energy that was released when individual protons and nucleus were bound together by strong force to form a nucleus. This is the same energy that would require to break a nucleus into nucleons.
What is the relationship between the binding energy and stability?
direct
Explain mass defect?
When nucleons bind together to form a nucleus, some mass is converted into energy, so the mass of the nucleus when you combine all the nucleons is less than the sum of individual nucleon masses. The difference is called mass defect
Mass defect and nuclear binding energy are different, True or false
True, but they are equivalent through Einstein’s equation for mass energy equivalence E = mc 2
What is the characteristic of a mass defect of a stable nucleus
It is always positive
How would you convert kg to joules?
Multiply by 9 x 10 ^16
Formula for nuclear binding energy?
E = mc2
In a nuclear domain, energy is expressed in volts?
Electronvolts, 1 ev = 1.6 10 ^ -29
What is c?
Speed of light (3.0 x 10^8)
Formula for nuclear binding energy in MeV?
m in amu x 931.5 ev, 1 emu = 1.66 x 10 ^ -27
What does emission spectrum display?
different wavelengths and energies of light for the gas passing through it
Formula for energy of a photon?
E = hf, h is planck’s constant (6.63 x 10^-34)
Frequency in terms of speed of light and wavelength formula?
F = c/wavelength
Explain Bohr’s model of atom?
- electrons in an atom orbited the nucleus like planets did the sun
- distance from the nucleus is related to the energy of the electrons, electrons with large energy orbited at greater distances.
- electrons in the atom cannot assume any arbitrary energy, but have quantized energy states.
- they only orbit at certain allowed distances from the nucleus.
Explain the phenomenon of jumping and dropping of an electron?
if an electron absorbs energy that is exactly equal to the different in energy between its current level and the one available at a higher level, it jumps to that higher level.
If an electron emits a photon with an energy exactly equal to the difference between its current level and the one at the lower energy.
Bohr’s model predicted that elements have line spectra instead of a continuous spectra. True/ False
True
An electron can absorb any amount of energy?
False, electron can only gain or lose specific amount of energy due to their quantized nature of energy levels
Define ground state? excited state?
It is where electron is initially, lowest possible energy level n = 1
when electron absorbs a photon and it jumps to a higher energy level
Excited electrons relax to the ground level in large jumps? t/f
False, they gradually lose energy and come to the ground state
Formula for energy levels of electrons?
E n = (-2.178 x 10 ^ -18) / n 2
What is Bohr’s atom
an atom that contains only one electron
Limitation of Bohr’s model of atom
cannot predict the line spectra of multiple electrons, cannot explain the electron-electron interactions
What does quantization of atoms describe?
Shell, sub-shell, orbital and spin number
higher shell electron has a greater amount of energy? T/F
True
Define orbital
3-D region around the nucleus where the electron is most likely to be found.
Define subshell
A subshell in an atom contains one or more orbitals with the same energy. It also describes the shape and energy of the orbitals. Subshells are s, p, d, f
what are degenerate orbitals
one or more orbitals of the same energy
orbitals of same energy have same 3-D orientation in space? T/F
False. The number of orientation increases by two in each successive subshells. 1 in s, 3 in p and so on
The number of orientations increases by two in each successive subshell? T/F
True, s subshell contains one orientation and p contains three
Describe the shape of s and p orbitals
s subshell has one spherical symmetrical orbital and p has three orbitals with different spacial orientations
describe electron spin states
two possible spin states (electron’s intrinsic magnetism). orbital with two electrons, one spins up and one spins down
3 rules of electron configuration?
Aufbau principle: electrons occupy the lowest energy orbitals available
Hund’s rule: electrons in the same sub shells occupy available orbitals singly before pairing up
Pauli principle: there can be no more than 2 electrons in a given orbital
maximum numbers of electrons in s, p, d, f subshell?
s has 1 possible orbital orientation, and there can be no more than 2 electrons in any given orbital
2 x 1 = 2 elections
p has 3 possible orbital orientation,
2x 3 = 6 electrons
d has 5
2 x 5 = 10
f has 7
2 x 7 = 14
Define diamagnetic
an atom that has its all of the electrons paired is called diamagnetic. these electrons cancel out each other’s magnetic field leaving the atom with no magnetic field. As a result, the atom will be repelled by an externally produced magnetic field
Define paramagnetic
when an atom’s electrons are not all spin-paired. these atoms are attracted to external magnetic field
difference between a period and group on the periodic table
period is horizontal row and group is the vertical column
difference between a period and group on the periodic table
period is horizontal row and group is the vertical column
Additional rules for d and f period while counting the configuration
for d block of period, subtract 1 from period number, outermost electrons are in 3d instead of 4d and for f period block, subtract 2 from the period number, instead of 8f it would be 6f
Name some atoms with anomalous electron configurations. (anticipated electron configuration is not one observed)
anomalous atoms can achieve a lower state of energy by having a filled or half filled d shell. These are chromium group, copper group atoms, pg -73
define isoelectronic?
F - has the same electron config. as Ne gas after gaining an electron. Atoms with the same configurations said to be isoelectronic.
When an atom becomes an anion, move right on the periodic table
When an atom becomes a cation, move left on the periodic table
Define the process of ionization (electrons being removed) from d group
To form a cation, atoms will always lose their valence electron first from s before they lose it from d
List special names for a group in periodic table
Group I : Alkali metals ( reducing agents)
Group II: Alkaline earth metals ( reducing agents)
Group VII: Halogens (oxidizing agents)
Group VIII: Noble gases
s, p blocks: representative elements
d blocks: transition metals
f blocks: rare earth metals
Define metalloids
Elements that posses the qualities of both metals and non metals. Example: B, Si, Ge, As, Sb, Te, Po
Define shielding
Each filled shell between the nucleus and the valence electrons shields the valence electrons from the full effects of the positively charged protons in the nucleus. Z eff: effective nuclear charge
Describe the atomic trends in the periodic table (atomic radius, ionization energy, electron affinity, electronegativity, acidity)
Atomic radius:
left to right: atomic radius decreases because more protons are applied higher effective nuclear charge on the electrons
top to bottom: atomic radium increases because more shells are being added and shielding increases
cation < neutral atom < anion
ionization energy: energy required to remove an electron. IE 1 for energy to remove the least tightly bound electron. IE2: energy to remove least tightly bound from the cation. IE2 > IE1
left to right and bottom to top - energy increases because the valence electrons are more tightly bound.
noble gases have large IE
Electron affinity: energy associated with add an electron. energy released: negative, energy absorbed: positive
halogens have large negative EA, more stable: release of energy
noble gases and alkaline earth metals have positive EA as adding an electron destabilizes them
more negative as we right and up (there are exceptions like noble gases)
Electronegativity : tendency to attract electrons
left to right: ENV increases
top to bottom: decreases
F>O>N=Cl>Br>I>S>C=H
Acidity: how well the compound donates protons
left to right: increases because more ENV more stable anion
top to bottom: increases, as the size increases
What does formal charge tell us? What is the formula?
If the atoms are sharing their electrons in the best way possible. This happens when the formal charge is as low as possible. FC = valence e - 1/2 bonding e - lone paired e (individual). Negative formal charges on the most electronegative elements
Describe resonance structure
These structures are often needed when there are double or triple bonds in molecules along with one or more lone pairs of electrons.
Define resonance hybrid
an average of the equivalent or non-equivalent lewis structures. The dotted line in the hybrid signifies a bond and a half
Define bond length
the distance between two nuclie that are bonded to one another
Define bond dissociation energy
energy required to break the bond homolytically (where one electron of the bond being broken goes to each fragment of the molecule and two radicals form)
Define heterolytic bond cleavage
both electrons that make up that bond end up on the same atom forming an anion and a cation.
Define bond order?
number of bonds between adjacent atoms, single bond = 1, double = 2, triple = 3
relationship between bond length and bond order
higher the bond order, shorter and stronger the bond
Carbon carbon bond lengths can be compared to carbon-oxygen bond lengths? T/F
False, bevause of the varying atomic radii the bond length and dissociation energy comparisons should be between similar bonds. Carbon - carbon can be compared to carbon-carbon only
describe the relationship between bond length and s and p charaters
the greater the s character, the shorter the bond because s-orbitals are closer to nucleus. p character leads to a longer bond that is farther from the nucleus
How is covalent bond formed?
Covalent bond is formed between atoms when each contributes one or more of its valence electrons. These electrons are shared by the atoms to help complete the octet.
When is a covalent bond polar and non-polar?
Polar bond when the electron density between two nuclei is uneven or when there is a greater difference between the ENV of the bonding atoms.
Non-polar when the electron density is even and there is a little difference between the ENV of two atoms that are bonded to each other.
what is a coordinate covalent bond?
one atom donating both the shared electrons in a bond. example NH3 bonding with BF3 in which N donates both of its lone pair to make a bond
what is Lewis base and Lewis acid?
a molecule that donates a pair of electrons is called Lewis base aka ligand aka nucleophile (nucleus loving). base is a diner
a molecule that accepts a pair of electrons is called Lewis acid aka electrophile (electron loving). acid is a acceptor
When a covalent bond breaks, the electrons from the ligand split between two molecules. T/F
False, electrons that come from a ligand leaves with a ligand.
How do you identify Lewis base?
Lewis base is a molecule with a pair of non-bonding electrons
What is an ionic bond
when two molecules are held together by the electrostatic attraction between a cation and anion.
What is one rule of VSEPR THEORY
SINCE ELECTRONS REPEL ONE ANOTHER, ELECTRON PAIRS MOVE FAR AWAY FROM EACH OTHER WHETHER THEY ARE BONDING OR NON-BONDING
what are some trends of ionic bonds
metal and non mental should have a big difference between their ENV to make an ionic bond
strength of an ionic bond is related to the charges on the ion. bigger charge, greater strength
the strength decreases as the ionic radii increase
CHARACTERISTICS OF A LINEAR SHAPE
ANGLE IS 180
WHAT ARE ELECTRON GROUPS
ANY TYPE OF BOND AND LONE PAIRS
WHAT DOES TOTAL NUMBER OF ELECTRON GROUP ON THE CENTRAL ATOM DETERMINES
THE BOND ANGLES AND ORBITAL GEOMETRY
IS ORBITAL GEOMETRY SAME AS MOLECULAR GEOMETRY?
NO, MOLECULAR GEOMETRY AKA SHAPE CHANGES WITH LONE PAIR INTO BENT AND IS NOT SAME AS THE ORBITAL GEOMETRY
What is the value of s character and p character in so, sp2 and sp3 hybridization?
sp - 50% s and 50% p
sp2 - 33% - s and 67 % p
sp3 - 25 % s and 75% p
what are the bond angles of three hybridization groups?
sp - 180
sp2 - 120
sp3 - 109.5
review khan academy notes on hybridization and steric number
What results in a polar molecule
When there are unsymmetrical polar bonds present in a molecule so they don’t get cancelled out. The atoms connecting the the central atom should have unequal ENV
List two forces that hold liquids and solids
Intermolecular molecular forces such as dipole-dipole and London dispersion forces
define intermolecular forces
weak interactions that take place between neutral molecules
define ion dipole forces
polar molecules are attracted to ions and create ion-dipole forces
define dipole dipole interactions
attraction between positive end of the polar molecule and the negative end of the polar molecule
define dipole induced dipole force
a permanent dipole in a molecule may induce a dipole in a neighbouring non polar molecule producing dipole induced dipole interactions
Define LDF
an instantaneous dipole in a non polar molecule induces a dipole in neighbouring non polar molecule. This results in LDF which are very weak and a default force in all atoms or molecules
How is molecular weight related to polarity
as the molecular weight increases, the polarity also increases
what is the relationship between dispersion forces and atomic size
direct, as the atomic size increases the dispersion forces also increase
How would stronger intermolecular forces effect meeting points, boiling points, viscosities and vapour pressure
high melting and boiling points, high viscosity, and lower vapour pressure
what are van Der Waals forces collectively and individually referring to
collectively - dipole-dipole, hydrogen bonding and LDF
individually - LDF
What are the 2 conditions of a hydrogen bonding
- a molecule must have a covalent bond between H and either NOF
2, the another molecule must have a lone pair of electrons on NOF atom
The boiling points of NOF bonded with H containing compounds is similar to other elements found in the similar groups?
T/F
False, the boiling point of the hydrogen containing compounds with NOF is much higher than the atoms found in the same group.
what is vapour pressure
pressure exerted by the gaseous phase of the liquid that evaporated from the exposed surface of the liquid
relationship between vapour pressure and IMF and boiling point
weaker the forces, higher the vapour pressure and more easily it evaporates
indirectly related to boiling point. the higher the boiling point the Lower the vapour pressure, it doesn’t boil easily.
what substances are said to be volatile
substances with high vapour pressure
relationship between vapour pressure and temperature
Direct
Define ionic solids
solid held together by electrostatic attraction between cation and anion in a lattice structure.
Strong and solid at room temp
intermolecular forces are similar to intramolecular forces
In an ionic solid, what determines the strength of the bond: charge of the ion or the size of the ion?
Charge of the ion
Define a network solid
atoms are connected in a lattice of covalent bonds (all interaction between the atoms are covalent bonds)
only has intramolecular forces
hard solid, very strong at RT