Chemistry - Physical

?
• Created by: Carkesden
• Created on: 04-05-17 20:01
• Physical Chemistry
• Fundamental particles
• Electron
• Relative charge: -1
• Orbits the nucleus in shells
• Relative Mass: 1/1840
• Proton
• Relative charge: 1
• Relative mass: 1
• In the nucleus
• Neutron
• Relative charge: 0
• Relative mass: 1
• Neutron
• Relative charge: 0
• Relative mass: 1
• Mass number is the total number of neutrons and protons.
• Atomic number is the number of protons in an atom (Also the number of Electrons)
• Time of Flight Mass Spectromitry
• Used to determine the mass of an atom or particle
• A positively charged ions are formed by the use of an electrospray ionisation
• Positively charged plates are used so that ions with the same kinetic energy 'fly'
• The velocity can be worked out by the distance over time.  As the detector measures the time of flight.
• Then the equation for kinetic energy can be used to to work out the mass
• Ek=1/2mV^2
• This is used to then work out what the relative atomic mass is.
• This can be used to work out the relative abundance and relative isotopic mass.
• This is done by a computer
• Different Isotopes of the same element can have different masses
• E.g Chlorine is 25% with a mass of 37 and 75% mass of 35, leaving with a mean mass of 35.5
• Electron configeration
• Electrons are 'in' different shells and sub shells.
• The shells and sub shells show area where it is probable that the electrons are in
• The sub shells are also called orbitals and are s, p, and d (and f).
• The energy required to remove the first electron is the first ionisation energy.
• Amount of substance
• Relative atomic mass: The ration of the average mass of one atom to one-twelfth of  carbon-12.
• The Avogadro constant is the number of particles in a mole.
• The mole is equal to 12 grams of carbon-12
• Ideal gas equation is pV=nRT. Can be used to work out pressure, volume, number of moles, and temperature.
• R is the gas constant and is equal to 8.314.
• Must be in SI units, pressure in Pa, volume in cubic metres, n is measured in mole and temperature in K.
• Empirical formula is the simplest whole number ratio of atoms of each element in a compound.
• Molecular formula is the actual number of atoms of each element in a compound
• Percentage atom economy is:
• Molecular mass of desired products/ sum of molecular mass of all reactants   X 100
• Relative molecular mass: the ratio of the average mass of one molecule of an element of compound to one twelfth of the mass of an atom of carbon-12
• Bonding
• Ionic bonding involves electrostatic attraction between charged ions in a lattice.
• Covalent bonding
• A single covalent bond is the sharing of a pair of electrons
• Multiple bonds contain multiple pairs of electrons.
• A co-ordinate bond contains a shared pair of electrons supplied by one atom
• Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice
• There are 4 different types of structures due to bonding: Ionic, metallic, macro-molecular and molecular.
• Pairs of electrons on the outer-shell arrange themselves as so that there is minimum repulsion
• Lone pair-Lone pair repulsion is greater than
• This affects the bond anges
• bond pair- bond pair repulsion.
• Lone pair- Bond pair repulsion which is greater than
• bond pair- bond pair repulsion.
• This affects the bond anges
• Electronegativity
• Electronegativity is the power to attract the pair of electrons in a covalent bonds
• This produces polar covalent bonds and may cause a permentant dipole
• Forces between molecules
• Permanent dipole-dipole
• Induced dipole-dipole
• Melting point and boiling point of molecular substances are affected by theses forces
• Permanent dipole-dipole
• Hydrogen Bonding
• Hydrogen Bonding
• Energetics
• Endothermic and Exothermic
• Exothermic reactions give out heat
• Endothermic reactions take in heat
• Enthaply changes
• In exothermic reactions the enthaply change is postive
• Exothermic reactions give out heat
• In endothermic reactions the enthaply change is negative
• Endothermic reactions take in heat
• Hess's Law
• Hess's law states that the enthaply  change for a chemical reaction is the same, whatever route is taken from reactants to products
• Enthalpy of formation
• Multiply depending on the top row, not the bottom row
• Enthaply of combustion
• Arrows go down
• Arrows go up
• Enthaply of combustion
• Arrows go down
• Bond enthaplies can be used to calculate enthalpy changes if reaction
• Equilibria
• Some reactions go backwards and forwards
• Equilibrium has some certain condtions
• Equilibrium can only be reached in a closed system
• It can be approached from either direction
• It is dynamic
• When macroscopic properties of the reaction do not change equilibrium has been reached
• Le Chatelier's Principle
• "If a system at equailibrium is distrubed, the equilibrium moves in the direction that tends to reduce the distrubance"
• If you increase the concentration of the products the equilibrium will move to the right
• If you change the pressure the equilibrium will move to the lessen the disturbance.
• If you increase the pressure, if there is more moles of reactants it wil move to the right and if there is more moles of the products it will move to the left
• Vice versa for decrease in pressure
• If you change the temperature it depends if the reaction is exothermic or endothermic
• If it is exothermic and you increase the temperature it will move left, Decrease temperature it will move right
• If it is endothermic and you increase the temperature it will move right, Decrease the temperature and it will go left
• Equilibrium is used in industry, a major use for it is ammonia although it is used in many other reactions
• Equilibrium constant, Kc
• The units can vary due to the equation
• Found by using the concentrations
• Changing conditions can affect the constant
• Temperature: Increase an exothermic Kc decreases. Increase an endothermic Kc increases. Vice versa for decrease in temperature
• Pressure: Does not affect Kc
• Catalysts: Does not affect Kc
• If Kc is greater than one then there is more products
• If Kc is less than one then there is more reactants
• Oxidation, reduction and redox reactions
• Oxidation is the loss of electrons
• Reduction is the gain of electrons
• Oxidations states
• Hydrogen = +1 (except in metal hydrides, where it is -1)
• Group 1 = +1
• Group 2 = +2
• Aluminium = +3
• Oxygen = -2 (except in peroxides where it is -1 and in the compound OF2 where it is +2)
• Fluorine = -1
• Chlorine = -1 (except in compounds with F and O where it has positive values
• Uncombined elements have oxidation states of 0
• The sum of all oxidation states in a compound = 0
• The sum of an oxidation state of a ion is equal to the charge of the ion
• in a compound the most electronegative element always has a negative oxidation state
• Oxidation states can be used in redox reactions
• To balance a redox reation the number of atoms of each element on each isde has to be equal. The tota charge on each sie of the equation must also be equal

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Physical Chemistry resources »