2804874
| Question | Answer |
| Initiation in free radical subs | production of free radicals - breaks homolytically - photochemical reaction |
| Propagation | reaction between a free radical and a molecule to make another free radical |
| Termination (FRS) | reaction between two free radicals making an unreactive molecule |
| Standard enthalpy of formation | the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states, under standard conditions |
| why is the enthalpy of formation of oxygen gas zero? | it is an element, in its standard state - can be applied to all other elements |
| Mean bond enthalpy | Standard molar enthalpy change of bond dissociation is the energy required to break a specific covalent bond. This varies between compounds, so an average is used |
| Standard enthalpy change of combustion | Enthalpy change when one mole of a compound is completely burnt in oxygen under standard conditions |
| Enthalpy change | Heat energy change measured at constant pressure |
| Hess's Law | the enthalpy change for a reaction is independent on the pathway taken from the reactants to products |
| Oxidation (in terms of electrons) | loss of electrons |
| Reduction (in terms of electrons) | gain of electrons |
| Oxidising power - trend in the halogens | - decreases going down the group - want to gain electrons. This is shown by displacement reactions |
| Halide ions as reducing agents | - increases going down the group - want to lose electron - larger = easier to lose electron |
| Halogens - Ionic radius | increases going down the group, increasing reducing power |
| why is the ionic radius larger than the normal atom? (in negative ion) | added electron repels others so radius gets larger |
| Disproportionation | redox reaction in which the oxidation number of some atoms of a particular element increases and others of the same element decrease |
| conditions needed for elimination | - no water present - hydroxide is dissolved in ethanol and mixed with haloalkane - hot - tertiary haloalkane |
| conditions needed for nucleophilic subs | - presence of water - cold - primary haloalkane |
| geometrical isomer | same structural formula but bonds are arranged differently in space |
| why are alkenes not used as fuels? | their reactivity makes them useful for other purposes |
| electrophile | - attracted to double bond - electron pair reciever - form carbocations |
| positive inductive effect | alkyl groups e.g. CH3 or C2H5 have a tendency to release electrons |
| Electrophilic addition steps | 1. formation of carbocation by electrophilic additon 2. rapid reaction with a negative ion |
| define: polymer | - long chain molecule made from many monomers - forms a chain with a very high Mr |
| why do alcohols have higher melting and boiling points than alkanes of a similar Mr? | addition of -OH means that there is hydrogen bonding between molecules |
| why are shorter chain alcohols soluble in water? | hydrogen bonding means that hydrogen bonds can form between water and -OH |
| Temperature | - the average kinetic energy of particles in a system - particles move faster, KE goes up and so does temp - temperature is independent of the number of particles present |
| Heat | - total energy of all particles present - dependent of amount of substance present - flows from high to low temp |
| Specific heat capacity | amount of heat needed to raise the temperature of 1g of substance by 1K |
| How does a flame calorimeter reduce heat loss? | - spiral chimney is made of copper - flame is enclosed - fuel burns in pure oxygen, rather than in air |
| bond dissociation energy | the enthalpy change required to break a covalent bond with all species in a gaseous state |
| Gangue | unwanted materials from ores such as clay and rock |
| Ore | an ore is a substance that contains enough metal for it to be economically viable to mine and extract |
| Roasting | process of converting sulfide ores to oxides by heating in air |
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