Chem IB1 exam

charlotteamannt's version from 2018-06-20 02:06

Section 1

Question Answer
Sublimation Solid to gas with no liquid state, energy absorbed
DepositionGas to solid with no liquid state, energy released
EvaporationLiquid to gas, energy absorbed, takes place only at surface of a liquid and can occur at temperatures below boiling point of liquid
BoilingLiquid to gas, energy absorbed
CondensationGas to liquid, energy released
Freezing Liquid to solid, energy released
MeltingSolid to liquid, energy absorbed
Moleculestwo or more atoms that are chemically bonded together, atoms can be the same. Electrically neutral
Homogeneoussame composition throughout
Heterogeneousnon-uniform composition
fractional distillationdifferent gases in air can be separated by a physical method. Each different component has its own boiling point,
SolutionsHomogeneous, solute dissolved in a solvent
Chemical reaction vs physical changeCr involve formation of new chemical substances. Pc only involve a change of state
Relative atomic massweighted average mass of an atom compared to 1/12 mass of an atom of carbon-12, unit: atomic mass unit (amu)
Isotope atom of same element with a different number of neutrons
Relative formula massweighted average mass of the compound compared to 1/12 the mass of an atom of carbon-12.
Molar mass (M) mass in grams of one mole of a substance, unit: g mol^-1
percentage yield(%=(actual yield/theoretical yield)×100
Boyle’s Law at constant temperature pressure and volume of a fixed mass of an ideal gas are inversely proportional to each other. So, if the pressure of a fixed mass of gas at constant temperature is doubled, volume halves. PV = k
Charles' Law at constant pressure the volume of a fixed mass of an ideal gas is directly proportional to its absolute temperature. V/T = k
Gay-Lussac's Lawat constant volume the pressure of a fixed mass of an ideal gas is directly proportional to its absolute temperature
combined gas lawPV / T = k
Ideal gasgases as largely empty space, containing randomly moving particles of negligible volume with weak or no intermolecular forces acting between them, obeys gas laws
Ideal gas equationPV=nRT, where: P: pressure in pascals (Pa), V: volume in m3, n: amount of gas (in mol), R: universal gas constant (8.314 J K–1 mol-1), T: absolute temperature (in kelvin).
Real gasesdeviate from ideal gas behaviour under 2 conditions: at high pressures and low temperatures (particles move slower intermolecular forces form)
standard solutionsolution with an accurately known concentration

Section 2

Question Answer
Atomic number (Z)number of protons in the nucleus of an atom
atomic orbitalregion of space where there is a high probability of finding an electron
Pauli exclusion principltwo electrons cannot have the same quantum number.
Heisenberg's uncertainty principleit is not possible to know, at the same time, the exact position and momentum of an electron. Instead, we can only state the probability that an electron will be somewhere in a given region of spac
Aufbau principle electrons fill atomic orbitals of lowest energy first
Exception to Aufbau principlechromium (Cr) and copper (Cu), both have 4s^1, instead e- goes to 3d
Hund's ruleelectrons fill orbitals in the same sub-level singly, before pairing up
relationship between wavelength and frequency. Higher energy = higher frequency = shorter wavelength.
continuous spectrumshows all the wavelengths or frequencies of visible light
absorption line spectrumsome of the wavelengths of visible light are missing, shown by the black lines on the coloured background
emission line spectrumcoloured lines on a black background

Section 3

Question Answer
periodicity repeating patterns of chemical and physical properties
covalent radiushalf the distance between two neighboring nuclei.
Atomic radiusDecrease -> , increase down
electrostatic attractionattraction btween + charged nucleus and the - charged electrons within an atom, depends on distance between nucleus and the electrons (the atomic radius) and the number of shielding electrons within the atom
first ionisation energy nergy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
first ionization energy trendgenerally increase -> and decrease down, increase in ionisation energy across a period is due to increase in nuclear charge and decrease in atomic radii. results in an increased attraction between nucleus and valence electrons. Decrease IE due to increase in atomic radius.increased distance results in a weaker attraction between nucleus and valence electrons of an atom.
Electronegativity attraction of an atom for a bonding pair of electron, increases -> , decreases down
first electron affinity energy released when one mole of electrons are added to one mole of gaseous atoms, exothermic
metallic characterdecreases ->. decrease in metallic character is due to increase in ionisation energy across a period. increases down as the ionisation energy decreases.
amphotericcan act as either an acid or a base

Section 4

Question Answer
Ionic bondingtransfer of one or more electrons from the outer shell of one atom to the outer shell of another atom, electrostatic attraction
anionsnegative, gain electrons
cationspositive, lose electrons
Volatilityhow easily a substance evaporates
hydrationchemical reaction in which a substance combines with wates
Covalent bondingelements with a difference in electronegativity of fewer than 1.8 units. atoms are held together by the electrostatic attraction that exists between the two nuclei and the shared pair of electrons
Polarity≥ 1.8 units= Ionic, 0.5 − 1.7 = Polar covalent, 0.0 − 0.4 = Non-polar covalent
Coordinate covalent bonds both the bonding electrons come from one atom
Delocalised electronsshared between more than two nuclei in a molecule
2 bonding domainslinear, bond angle 180
3 bonding domainstriangular planar, angle 120
4 bonding domainstetrahedral, 109.5
2 bonding domains + 1 lone pair (3 e- domains)bent, 119.3
2 bonding domains + 2 lone pairs V-shaped , 104.5
3 bonding domains + 1 lone pairTrigonal pyramidal, 107.8
Allotropeifferent forms of the same element in the same physical state.
DiamondEach carbon is covalently bonded to 4 other carbons in a tetrahedral.iamond is a very hard substance with a high melting and boiling point. It is a poor electrical conductor as it has no delocalised electrons within its structure.
Graphite carbon atom is covalently bonded to three other carbon atoms. Graphite has a layered structure consisting of carbon atoms arranged in fused hexagonal rings. held together by relatively weak London dispersion forces. Each carbon atom has an electron which becomes delocalised across the plane. The presence of delocalised electrons explains the ability of graphite to conduct electricity along the plane of the crystal when a voltage is applied. Soft
C60 fullerinemade up of carbon atoms bonded together in 20 hexagons (six carbon rings) and 12 pentagons (five carbon rings). ach carbon atom is covalently bonded to 3 other carbon atoms. Presence of delocalized e- = conductor but not as well as graphite
Graphene composed of single layers of graphite with a bond angle of 120o between the carbon atoms in a trigonal planar arrangement. high electrical and thermal conductivity
London dispersion forcesweakest, London dispersion forces consist of temporary or instantaneous dipoles and induced dipoles.
Dipole-dipole forcesonly exist between polar molecules that have a permanent dipole
Hydrogen bondingstrongest, ccurs between molecules that have an electronegative nitrogen, oxygen or fluorine atom directly bonded to a hydrogen atom
Alloy homogenous mixtures composed of two or more metals or a metal and a non-metal, often stronger, more chemically stable and often more resistant to corrosion

Section 5

Question Answer
enthalpy (H)heat content of a system is
temperatureaverage kinetic energy of the particles in a substance
closed systemonly energy is able to move between the system and the surroundings
exothermicWhen heat is transferred to a system from the surroundings,
Endothermicreaction in which heat is absorbed, enthalpy of the system increases, so ΔH is positive
specific heat capacity (camount of heat required to raise the temperature of one gram of a substance by one degree Celsius or one kelvin
Enthalpy changeq = mc∆T, q is the heat absorbed or released in J
enthalpy change of neutralisation (ΔHn)enthalpy change when an acid and base react together to form one mole of water.
standard enthalpy of combustion (ΔHƟc)enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions
Hess’s law total enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place, as long as the initial and final conditions are the same.
standard enthalpy change of formation (ΔHƟf ) enthalpy change when one mole of a compound is formed from the elements in their standard states under standard conditions, ΔHƟ = ΣΔHƟf (products) − ΣΔHƟf (reactants)
bond enthalpy E energy required to break a chemical bond
average bond enthalpy enthalpy change when one mole of bonds are broken in the gaseous state averaged for the same bond in similar compounds. ΔH = ΣE(bonds broken) − ΣE(bonds formed)
free radicalhighly reactive species due to the presence of an unpaired electron
lattice enthalpyenthalpy change when one mole of a solid ionic compound breaks down to form gaseous ions under standard conditions.

Section 6

Question Answer
Collision theory rule 1Reactant particles must collide.
Collision theory rule 2Reactant particles must collide with the correct orientation
Collision theory rule 3Reactant particles must collide with energy equal to or greater than the activation energy.
activation energy (Ea)minimum amount of kinetic energy that colliding particles must have for a chemical reaction to occur.
Catalystused to increase the rate of chemical reactions. They achieve this by providing an alternative reaction pathway that has a lower activation energy than the uncatalysed pathway. Remains chemically unchanged at end of reaction
rate of reactionchange in concentration of a reactant or product per unit of time

Section 7

Section 8