General Flashcards
What is the test for 3° alcohols to isolate them from 1 and 2
Add K2Cr2O7 (stays orange for 3°, 1° and 2° react so colour changes to green
Equation for enthalpy change of formation
(Sign) mass of Liquid x 4.18 x change in temp/1000 x lim moles
Define enthalpy change of formation
Enthalpy change when 1 mole of a substance is formed from its elements under standard conditions
Define Enthalpy change of combustion
Enthalpy change when one mole of a substance is completely combusted under standard conditions
Equation for enthalpy change of combustion
(Negative) (mass of H2O x 4.18 x change in temp)/(1000 x mol fuel)
Effect of ozone in stratosphere
Absorbs high energy UV
Effect of ozone in troposphere
Photochemical smog, respiratory problems
Physical properties of haloalkanes
Covalent bonding, simple molecular structure, usually liquid at RTP, don’t mix well with water
Group 2 physical properties
High mpt/bpt, density greater than group 1 elements
Group 2 reaction with water observations
Silver solid reacts with effervescence to produce cloudy solution (alkaline)
Group 2 oxides reaction with H2O?
Produces hydroxides
Acid + Base -> ?
Salt + Water
Group 2 trends down group
Solubility of Carbonates decreases, everything else increases (reactivity, thermal stability etc.)
How are emission spectra formed
Atom heated to high temperature, electrons excited to higher energy level, energy given out as em rad when electrons drop back down, rad passed through prism coloured lines seen
How are absorption spectra formed
White light passes through cooled sample of gas, energy absorbed to raise electrons to higher energy levels, rad passed through prism, black lines show missing frequencies
What shape are s and p orbitals
S - spherical, P - dumbbell shaped
What are subshells
Groups of orbitals of the same type
Define covalent bonding
Electrostatic attraction between shared pairs of electrons and two positive nuclei
Exceptions to covalent bonding rule
H forms 1 bond, Be forms 2 cov bonds, Al forms 3 cov bonds, S can form 2 or 6, P can form 3 or 5
Define metallic bonding
Electrostatic attraction between a lattice of positive ions and a sea of delocalised electrons
Define ionic bonding
Electrostatic attraction between ions of opposite charges
What structure do ionic compounds have
Giant 3D lattice
How do ionic compounds dissolve in water
Water molecules cluster around the ions, positive ions are attracted to O and negative ions attracted to H, water molecules overcome bonds in the compound and pull the ions apart
Define stereoisomerism
Compounds with the same structural formula but with a different arrangement
What are E/Z isomers
When there is no free rotation about the C=C bond, with two different groups attached to each C atom including one H on each carbon
Conditions for cracking
500°c, Al2O3 catalyst, no O2
How do homogenous catalysts work
Reactant gas absorbs on the catalysts surface
Bonds in reactant molecules are weakened and break
New product bonds form
The product molecules desorb from the surface
Physical properties of alkanes
Low mpt/bpt
Insoluble in water
Soluble in organic solvents
Less dense than water
Chemical properties of alkanes
Generally unreactive
Non polar
Strong C-C and C-H bonds
How to balance half equations
Balance atoms other than O and H
Add H2O to balance O
Add H+ to balance H
Add e- to balance charge
How do IdId bonds form
Electrons constantly moving
Causes uneven distribution of charge
Causes instantaneous dipole in 1
Induces other dipoles in neighbouring molecules
What are PdPd bonds
Attraction between molecules with permanent dipoles
Only in polar molecules
Which solvents do polar/nonpolar molecules dissolve in
Polar dissolves in polar
Nonpolar dissolves in nonpolar
How do PdId bonds form
A permanent dipole can induce a temporary one in a species that is normally non polar such as HCl and Cl2
What is Hydrogen Bonding
A type of strong PdPd bond
Electrostatic attraction between a very delta+ H atom and a LP of e- on a N O or F atom
Very high mpt bpt
Strength depends on electronegativity and number of H bonds
What radiation does the sun emit
Mainly UV with some visible
What is a nucleophile
A negative or partially negative species that forms a dative bond by donating a pair of electrons
Define electronegativity
A measure of the ability of an atom to attract the bonding pair of electrons in a covalent bond to itself
Solubility of Nitrates and Ethanoates
All are soluble
Solubility of Sulphates
All soluble except
BaSO4, PbSO4, CaSO4
Solubility of Halides
All soluble except
AgX and PbX
Solubility of Carbonates
All insoluble except
Na, K, NH4
Solubility of Hydroxides
All insoluble except
Li, Na, K, Ca
Solubility of Oxides
All insoluble
Group 1 and 2 oxides react with water to form hydroxides
Carbonate test
Add an acid, effervescence
Bubble gas through lime water
Goes from colourless to cloudy white
Sulphate test
Nitric acid and Barium nitrate
White precipitate
Halide ion test
Nitric Acid, Silver Nitrate
Cl- White Precipitate
Br- Cream precipitate
I- Yellow precipitate
Physical properties of alcohols
Polar
Higher mpt/bpt than alkanes
Small alcohols are water soluble
Define ionisation energy
Energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms
What order should anion tests be carried out (Sulphate, Carbonate, Halide)
Carbonate
Sulphate
Halide
