C3 - Chemicals of the Natural Environment Flashcards
Describe the chemical bonds found in
metals
Describe the chemical bonds found in metals
- Metallic bonding.
- Many positive metal ions fixed in a giant regular
structure surrounded by a sea of delocalised
negative electron. - There is strong electrostatic attraction between
opposite charges.
What are the general properties of
metals?
What are the general properties of metals?
- High melting points
- Solid at room temperature
- Strong and hard
- Malleable (can be pressed into shape)
- Ductile (can be drawn into wires)
- Good electrical and thermal conductors
Why do metals have high melting points?
Why do metals have high melting points?
Lots of energy is required to overcome
the many strong metallic bonds.
Why are metals hard?
Why are metals hard?
Very strong metallic bonds hold the giant
structure together.
Why are metals malleable and ductile?
Why are metals malleable and ductile?
Metals are made up of uniform layers of
atoms which can easily slide over one
another. So the shape of the metal can
be easily changed.
Why are metals good conductors?
Why are metals good conductors?
The delocalised electrons are free to
move to carry charge.
Write the general equation for the
reaction of metals with water
Write the general equation for the reaction of metals
with water
metal + water → metal hydroxide + hydrogen
Write the general equation for the
reaction of metals with dilute acid
Write the general equation for the reaction of metals
with dilute acid
metal + acid → salt + hydrogen
What is a displacement reaction in terms
of metals?
What is a displacement reaction in terms of metals
?
A reaction in which a more reactive metal
displaces (replaces) a less reactive
metal from a compound.
How can the order of the reactivity of
metals be deduced from the results of an
experiment?
How can the order of the reactivity of metals be
deduced from the results of an experiment?
More reactive metals can displace less
reactive metals from their compounds in a
displacement reaction. A series of
displacement reactions can be carried out to
compare the reactivities of metals.
What is meant by the reactivity of
metals?
What is meant by the reactivity of metals?
The tendency of a metal atom to lose
electrons and form its positive ion.
Which metal in the reactivity series
reacts with water most vigorously?
Which metal in the reactivity series reacts with water
most vigorously?
Potassium
Reactivity series
Potassium MOST REACTIVE Sodium Calcium Magnesium Aluminium Zinc Iron Lead (Hydrogen) Copper Silver LEAST REACTIVE
Using the reactivity series, which elements don’t
react with acids?
Which elements don’t react with acids?
Copper and silver because they are below hydrogen in
the reactivity series so are less reactive than hydrogen.
What is the principle of conservation of
mass?
What is the principle of conservation of mass?
A closed system has a constant mass
during a reaction, no matter is gained or
lost, so the mass of reactants is equal to
the mass of products.
Write a balanced symbol equation for the
displacement reaction between calcium
and copper(II) sulphate
Write a balanced symbol equation for the
displacement reaction between calcium and copper(II) sulphate
Ca(s) + CuSO4(aq)→ CaSO4(aq) +Cu(s)
Write the ionic equation for the reaction
between sodium and iron(II) carbonate
Write the ionic equation for the reaction between
sodium and iron(II) carbonate
2Na(s) + Fe2+(aq) → 2Na+(aq) + Fe(s)
What is an ore?
What is an ore?
A rock that contains a mineral that can
be extracted.
Which metals can be extracted from their
ores by heating with carbon?
Which metals can be extracted from their ores by
heating with carbon?
Metals which are below carbon in the reactivity series,
such as zinc
Describe how zinc can be extracted from
its ore
Describe how zinc can be extracted from its ore
Heat zinc oxide with carbon to reduce it
and form zinc. Carbon is the reducing
agent and is oxidised. Carbon displaces
zinc from its oxide.
Write a word and symbol equation for the
reduction of zinc oxide with carbon
Write a word and symbol equation for the reduction
of zinc oxide with carbon
zinc oxide + carbon → zinc + carbon monoxide
ZnO(s) + C(s) → Zn(l) + CO(g)
Why must electrolysis be used to extract
some metals from their ores?
Why must electrolysis be used to extract some
metals from their ores?
Metals above carbon in the reactivity series are more reactive than carbon so they will not be displaced from their ores by carbon.
Why is electrolysis not used to extract
zinc from its ore?
Why is electrolysis not used to extract zinc from its
ore?
- Zinc is less reactive than carbon so can
be extracted by heating with carbon. - Electrolysis is expensive and requires a
lot of energy.
How can plants be used as an
alternative metal extraction method?
How can plants be used as an alternative metal
extraction method?
Phytoextraction:
Plants are grown in areas with metals in the soil. The
plants take up metals through their roots and
concentrate them in their shoots and leaves. These
plants are burned and the metals are removed from the
ash.
How can bacteria be used as an
alternative metal extraction method?
How can bacteria be used as an alternative metal
extraction method?
Bacterial extraction:
Some bacteria absorb metal compounds. These
bacteria produce solutions called leachates
containing the metals. Scrap iron can be used to
remove the metal from the leachate.
What are the limitations of biological
methods of extraction?
What are the limitations of biological methods of
extraction?
- Produces smaller quantities of metals.
- Slow processes.
- Require displacement or electrolysis for the final
step.
- Bacteria require acidic conditions and may introduce
toxic substances to the environment.
When do ionic compounds conduct
electricity? Why?
When do ionic compounds conduct electricity? Why?
When molten or aqueous (dissolved in water)
because the ions are free to move. When solid,
the ions are fixed in the lattice so they can’t
move to carry a charge.
What is an electrolyte?
What is an electrolyte?
A molten or aqueous ionic compound
that conducts electricity.
What is electrolysis and what can it be
used for?
What is electrolysis and what can it be used for?
Electrolysis is the decomposition of an
electrolyte using an electric current. It
can be used to extract metals from their
ores.
When using inert electrodes, what
happens at the cathode?
When using inert electrodes, what happens at the
cathode?
Cations (positive ions) move towards the cathode
(negative electrode). Positive metal ions gain electrons
to form metal atoms. If the metal is more reactive than
hydrogen, hydrogen will form at the cathode instead
and the metal will remain in the electrolyte.
When using inert electrodes, what
happens at the anode?
When using inert electrodes, what happens at the
anode?
Anions (negative ions) move towards the anode (positive electrode). Negative non-metal ions lose electrons to form non-metal atoms.
Predict what will form when molten
lead(II) bromide is electrolysed
Predict what will form when molten lead(II) bromide
is electrolysed
Lead atoms (Pb) at cathode. Bromine molecules (Br2) at anode.
Write half equations for the reactions that
take place when calcium chloride
undergoes electrolysis
Write half equations for the reactions that take place
at each electrode when calcium chloride undergoes
electrolysis
Cathode: Ca2+ + 2e- → Ca
Anode: 2Cl- → Cl2 + 2e-
Describe oxidation and reduction in
terms of electrons
Describe oxidation and reduction in terms of electrons Oxidation is loss of electrons. Reduction is gain of electrons. OILRIG
How can electrolysis be used to extract
aluminium from its ore bauxite?
How can electrolysis be used to extract aluminium
from its ore bauxite?
- Purified to form aluminium oxide.
- Dissolved in molten cryolite.
- Insert inert electrodes and connect to power supply.
- Aluminium ions gain electrons at cathode to produce
pure aluminium and oxide ions lose electrons to form
oxygen at anode.
Why is aluminium oxide dissolved in
cryolite during electrolysis?
Why is aluminium oxide dissolved in cryolite during
electrolysis?
- Cryolite has a lower melting point than
aluminium oxide. - Aluminium oxide is insoluble in water.
- Reduces energy use and cost.
Why must the inert graphite electrodes
be replaced regularly when aluminium is
being extracted from its ore?
Why must the inert graphite electrodes be replaced
regularly when aluminium is being extracted from its
ore?
The oxygen produced at the anode reacts with carbon in the electrode forming carbon dioxide meaning carbon is lost from the anode.
When would oxygen not be produced at
the anode during the electrolysis of an
aqueous ionic compound? What would
form instead?
When would oxygen not be produced at the anode
during the electrolysis of an aqueous ionic
compound? What would form instead?
When halide ions are present (chloride,
bromide or iodide ions). A halogen would
form (chlorine, bromine or iodine).
Write the balanced half equation for the
formation of oxygen from hydroxide ions
at the anode
Write the balanced half equation for the formation of
oxygen from hydroxide ions at the anode
4OH- → 2H2O + O2+ 4e-
Describe how to carry out electrolysis on
an aqueous salt solution
Electrolysis on aq salt solution
- Pour the salt solution into a beaker.
- Insert 2 graphite electrodes and connect to a power supply.
- Fill 2 test tubes with salt solution and place over the
electrodes to collect any gas produced. - Turn on the power supply, ensuring the electrodes don’t
touch. - Turn off power and test gases.
What is a hydrocarbon?
What is a hydrocarbon?
A compound made up of only hydrogen
and carbon atoms.
Crude oil is the main source of _________
Crude oil is the main source of hydrocarbons
What is crude oil a feedstock for?
What is crude oil a feedstock for?
The petrochemical industry
Is crude oil finite or infinite?
Is crude oil finite or infinite?
Finite
Why is modern life dependent on
hydrocarbons?
Why is modern life dependent on hydrocarbons?
Hydrocarbons are a source of fuel which
is relied on heavily for modern life.
What is a homologous series?
What is a homologous series?
A series of organic molecules with the same general
formula. Successive members in the series differ by
-CH2.
Molecules in a homologous series have similar chemical properties because they have the same general formula.
What is the general formula for the
alkane homologous series?
What is the general formula for the alkane
homologous series?
CnH2n+2
What is a fraction of crude oil?
What is a fraction of crude oil?
A mixture of similar-sized hydrocarbon molecules with similar boiling points. These compounds are generally members of the alkane homologous series and have the formula CnH2n+2.
Why can crude oil be separated by
fractional distillation?
Why can crude oil be separated by fractional
distillation?
Because the different hydrocarbons have
different boiling points so condense at
different temperatures.
Describe the fractional distillation of
crude oil
Describe the fractional distillation of crude oil
- Crude oil is heated and evaporates.
- Crude oil vapours enter and rise up a fractionating
column which is hot at the bottom and cold at the top.
- Vapours condense when the temperature is below its
boiling point.
- Separated liquids leave the column at different heights.
Do the longest hydrocarbons leave the
fractionating column at the top or
bottom?
Do the longest hydrocarbons leave the fractionating
column at the top or bottom?
Bottom
Which forces must be overcome for
alkanes to turn from liquid to gas? What
other bond is found in alkane molecules?
Intermolecular forces must be overcome for an alkane to evaporate.
Covalent bonds are found between carbons and
between carbon and hydrogen. These are not broken
during boiling.
Why do different alkanes have different
boiling points?
Why do different alkanes have different boiling
points?
- Longer hydrocarbons have stronger
intermolecular forces. - More energy is required to overcome the stronger
forces. - Longer hydrocarbons have higher boiling points.
What is meant by the term empirical
formula?
What is meant by the term empirical formula?
The simplest whole number ratio of
atoms of each element in a compound.
What is the empirical formula of C4H10?
What is the empirical formula of C4H10?
C2H5
What is a covalent bond?
What is a covalent bond?
A bond formed from a shared pair of
electrons between atoms.
What are the limitations of using dot and
cross diagrams to represent covalent
compounds?
What are the limitations of using dot and cross
diagrams to represent covalent compounds?
- Don’t show the 3D arrangement of
atoms in space. - Doesn’t show the size of atoms
relative to one another.
What are the limitations of using 3D
diagrams to represent covalent compounds?
What are the limitations of using 3D diagrams to represent covalent compounds? - They are not show to scale. - Don’t show how the bond formed. - Don’t show the shared pair of electrons.
Which is stronger: covalent bonds or
intermolecular forces?
Which is stronger: covalent bonds or intermolecular
forces?
Covalent bonds
Why do alkanes have low melting and
boiling points?
Why do alkanes have low melting and boiling points?
During melting and boiling, intermolecular
forces are overcome but covalent bonds
aren’t broken. Intermolecular forces are
relatively weak compared to covalent bonds
so require little energy to overcome.
What is cracking?
What is cracking?
Breaking long chain hydrocarbon
molecules into smaller hydrocarbons.
What are the products of cracking?
What are the products of cracking?
Alkanes and alkenes
Alkenes are a different homologous
series containing a carbon to carbon
double bond.
Hexane is cracked to form butane and
ethene. Write a word and symbol
equation for this reaction.
Hexane is cracked to form butane and ethene. Write
a word and symbol equation for this reaction.
hexane → butane + ethene
C6H14 → C4H10 + C2H4
Describe what happens during cracking
Describe what happens during cracking
An alkane is heated. The vapours pass
over a catalyst and the covalent bonds
break and reform.
Why is cracking important?
Why is cracking important?
- The shorter chained alkanes and alkenes are in
higher demand than long chained alkanes. - Can match the supply of fractions with demand.
Typically fractional distillation of crude oil produces
too many long chain hydrocarbons. - Alkenes can be produced for use as a feedstock in
the petrochemical industry.
Alkanes are saturated hydrocarbons.
Explain what this means
Alkanes are saturated hydrocarbons. Explain what
this means
Hydrocarbon - contains only hydrogen and
carbon.
Saturated - carbon atoms are all joined by
single bonds.
What is an alkene? Include the general
formula and functional group
What is an alkene? Include the general formula and
functional group
An unsaturated hydrocarbon.
General formula: CnH2n
Functional group: C=C
Give examples of molecules that alkenes
react with in an addition reaction
Give examples of molecules that alkenes react with
in an addition reaction
React with water when heated with a catalyst to
form alcohols.
React with bromine to form bromoalkanes.
React with other alkenes to form addition
polymers.
What are the general formula and
functional group of an alcohol?
What are the general formula and functional group of
an alcohol? (Chemistry only)
General formula: CnH2n+1OH
Functional group: OH
What are the common reactions of
alcohols?
What are the common reactions of alcohols?
- Complete combustion, producing
water and carbon dioxide. - Oxidation to produce carboxylic acids
(needs an oxidation agent).
What are the general formula and
functional group of a carboxylic acid?
What are the general formula and functional group of
a carboxylic acid?
General formula: CnH2n+1COOH
Functional group: COOH
What do carboxylic acids react with?
What do carboxylic acids react with? - Metals (forms salt and hydrogen). - Bases (forms salt and water). - Carbonates (forms salt, water and carbon dioxide).
Why do members of a homologous
series react similarly?
Why do members of a homologous series react
similarly?
Because they all contain the same
functional groups.
Predict the formula of the products when
pentane is completely combusted
Predict the formula of the products when pentane is
completely combusted
H2O and CO2
Write a balanced symbol equation for the
incomplete combustion of ethane
Write a balanced symbol equation for the incomplete
combustion of ethane
C2H6 + 2O2 → 3H2O + C + CO
C2H6 + 2½O2 → 3H2O + C + CO2
C2H6 + 2½O2 → 3H2O + 2CO
Or any other balanced symbol equation where the products include H2O and C or CO. Products may also contain CO2 with C or CO.
Predict the formula of the product when
propene reacts with bromine
Predict the formula of the product when propene
reacts with bromine
C3H6Br2
Predict the formula of the products when
ethanol is oxidised
Predict the formula of the products when ethanol is
oxidised
Alcohols are oxidised to form carboxylic
acids.
Ethanoic acid: CH3COOH
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