a2 chem

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  • Created by: emma
  • Created on: 17-04-13 13:52
what is a lewis acid?
an electron pair acceptor
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what is a lewis base?
an electron pair donor
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why does adding a small amoun of ammonia give the same result as adding a small amount of hydroxide?
ammonia reacts with water to give ammonium ions and hydroxide ions. as hydroxide ions form, these then react.
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how do impurities poison heterogeneous catalysts?
impurities bind to active sites on the catalysts surface and prevent reactants from being adsorbed. this reduces the surface area of the catalyst available to reactants, slowing down the reaction.
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give two examples of catalyst poisoning
lead poisons catalyst in catalytic converters. sulfur poisons the iron catlyst in the harber process. it is adsorbed on to the iron forming iron sulfide, preventing the catalyst from catalysing the reaction efficiently.
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how does a homogenoeus catalyst work?
be forming an intermediate species> reactant + catalyst --> intermediate. intermediate then reacts to form products. activation energy of these two reactions lower than that needed to make the products from the reactants.
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what is autocatalysis?
when one of the products acts as a catalyst for the reaction.
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how do heterogeneous catalysts work?
they are in a different phase to the reactants. the reaction happens on their surface (reactants are adsorbed)
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what are the two ways of oxidising Co2+
with hydrogen peroxide in alkaline conditions, or with air in ammonical solution. [Co(NH3)6]2+ is formed and then oxidised to 3+ by oxygen in air.
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why are complex ions of transition metals coloured?
attachment of ligands splits 3D shell into two energy levels. e- occupy lower orbital. visible light\/
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how does a homogenoeus catalyst work?
be forming an intermediate species> reactant + catalyst --> intermediate. intermediate then reacts to form products. activation energy of these two reactions lower than that needed to make the products from the reactants.
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what is autocatalysis?
when one of the products acts as a catalyst for the reaction.
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how do heterogeneous catalysts work?
they are in a different phase to the reactants. the reaction happens on their surface (reactants are adsorbed)
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what are the two ways of oxidising Co2+
with hydrogen peroxide in alkaline conditions, or with air in ammonical solution. [Co(NH3)6]2+ is formed and then oxidised to 3+ by oxygen in air.
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why are complex ions of transition metals coloured?
attachment of ligands splits 3D shell into two energy levels. e- occupy lower orbital. visible light\? electrons jump to hte higher orbitals. freq of light absorbed depends on energy gap. rest of freq reflect. reflected complements absorbed.
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how can we find concentrations of transition metals using spectrometry?
white light shone through filter that only lets light absorbed by sample through. passes through to colorimeter. calculates how much light was absorbed. more concentrated= more light absorbed.
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what is a calibration graph?
measure absorbances of known concentrations of substance and plot on graph. measure absorbance of your sample (colorimeter) and measure concentration off graph.
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what is a complex?
a metal ion surrounded by coordinatley bonded ligands.
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what shape is cis-platin?
square planar
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whatever has the more negative electrode potential is...
oxidised (backward)
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whatever has the more positive electrode potential is...
reduced (forward)
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E cell =
E right - E left
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why does changing conditions change electrode potential?
it is an equilibrium reaction. changing conditions changes the position of equilibrium
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why are standard conditions used to measure electrode potentials?
if you measure understandard conditions, you will always get the same electrode potential for a paticular cell. measuring under standard conditions allows values for different cells to be compared
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sodium = water -->
NaOH, forming a very alkaline solution
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magnesium + cold water -->
slow, weakly alkaline solution ( magnesiu, hydroxide not very soluble --> relativley few hydroxide ions produced ) shows that reaction has occured
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magnesium + steam
more energy, reaction much faster, magnesium oxide produced
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sodium and oxygen -->
vigorous reaction in air to form Na2O , burns with yellow flame
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Mg and oxygen
MgO , viorous in air, brillant white flame.
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Al and Oxygen
Al2O3 reacts slowly in air no flame
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SI and oxygen
SiO2 reacts slowly in air, no flame
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P and O
P4O10 spontaneously combusts with brilliant white flame
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S and O
SO2 , burns steadily, Blue flame
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Other cards in this set

Card 2

Front

what is a lewis base?

Back

an electron pair donor

Card 3

Front

why does adding a small amoun of ammonia give the same result as adding a small amount of hydroxide?

Back

Preview of the front of card 3

Card 4

Front

how do impurities poison heterogeneous catalysts?

Back

Preview of the front of card 4

Card 5

Front

give two examples of catalyst poisoning

Back

Preview of the front of card 5
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