Chapter 6 Flashcards
% yield
actual yield/EXPECTED YIELD X 100
purity %
mass of pure product / mass of impure product x100
endothermic
gains energy, absorbs
exothermic
gives off, exserted, lost
combustion reaction
combustion of fossil fuels gas and oil = exothermic
fossil fuels are so useful because:
-they can be easily ignited and burnt
-they are capable of releasing large amounts of energy as heat
examples of exothermic reactions
photosynthesis,thermal decomposition of limestone
heat of reaction
-the energy change from reactants to product in a chemical reaction
-heat of reaction = delta aitch - triangle symbol
unit of heat change = kj (kilojoules)
1kj = 1000j
-calculation per mole of compound = kj/mol
breaking and making bonds
heat energy triangle H = heat energy = energy difference
-triangle H = energy required to break bonds - energy required to form bonds
catalyst
haber process =IRON
contact process= Vanadium oxide
hydrogenation of fats =Nickel
oxidation of NH3 =Platinum - Rhadium
alcoholic drinks industry=Enzymes (yeast)
conversion of methanol to hydrocarbons = Zeolite
heat of combustion
is the change of a reaction when a substance is burnt
usage of a metal calorimetry
how to measure heat of combustion *how much is lost
-insulator to not lose heat to surroundings
rate of reaction
speed = distance / time = km/hr -
-how concentrations of reaction changes over time = rate of reaction
factors affecting rate of reaction
- surface area of solid reactants
- concentration
- temp
- catalyst
- light on some reactions
surface area
increase = quicker rate of reaction
concentration
increase = faster rate of reaction = more molecules of reactants in solution
temp
increase = rate of reaction increases = kinetic energy = more collisions
catalyst
: substance that speeds up the rate of chemical reaction and is unchanged at the end
eg: decomposition of hydrogen peroxide = h2o2 =2h2o + o2
at room temp reaction is very slow
manganse (iv) oxide = MnO2 is used as a catalyst
catalyst converter
is a device for converting polluting exhaust gases from cars into less dangerous emissions
= removes polluting oxides and completes oxidation of unburnt hydrocarbon fuels
honey combed surface
converter contains a thin coating of rhadium and platium catalyst on a solid honeycombed surface
biological catalysts
protein molecules called enzyme -living cells also produce enzymes
they are specific
sensitive to temp *above 45 degrees, denatured and inactive
senitive to pH (7)
these catalyst are used to make washing soup/powders - removes blood, stains ,sweat 30-40 degrees
solid catalyst
different reactions need different catalysts
- one broad groupf of catalysts work on absorbing molecules on to the solid surface (BRINGS MOLECULES OF REACTANTS CLOSER)
- it is also thought the process of absorption weaken bonds in reactants molecules = this increases frequency of collision and molecules likely to react
activation energy
-energy required to start a chemical reaction
for reaction to take place=colliding partials must posses at least this amount of energy
-all reactions have activation energy = minimum energy required by reactants to from products
-catalysts increases rate of reaction by reducing energy required to break bonds
biomass
the energy stored directly by plants through photosynthesis
- provides food and warmth
- can be changed into fossil fuels by heat and pressure
respiration
c6h1206 + 6o2 = 6co2 + 6h2o
