DF.a-u - Developing Fuels | DF1-11
DF.Q Exam questions from past papers
Explain why the C=O double bond is shorter ● there are more electrons between the atoms in
than the C–O single bond (2) the double bond (1)
● giving greater attraction between the bonded
atoms (1)
● Comes from crops which can be regrown (1)
● Plants take in CO2 for photosynthesis (1) which
balances out roughly with CO2 produced on
burning (1)
Explain why biofuels are regarded as a
sustainable energy source and why they are
often describes as ‘carbon neutral’ (3)
When biodiesel burns it produces less carbon
monoxide than similar fuels made from crude Oxygen atom in structure allows more complete
oil. combustion therefore carbon dioxide produced (1) which
Explain why less carbon monoxide is produced is more fuel efficient (1) and this is desirable as CO is
and why this is desirable? toxic (1)
Compare
C2H5OH + 3O2 -> 2CO2 + 3H2O (ethanol)
C2H6 + 3.5O2 -> 2CO2 + 3H2O (ethane)
,Why can’t the enthalpy change for a thermal As thermal decomposition requires heat
decomposition reaction be measured directly?
NaHCO3 and Na2CO3 are ionic so not all bonds are
covalent (1)
Why can bond enthalpies not be used to
estimate ΔH1? (1)
2NaHCO3 (s) -> Na2CO3 (s) + CO2 (g) + H2O (l)
● Mr of C8H16 = 112
● Moles in one kg = 1000/112 = 8.93
● KJ per kg = 8.93 x 5300 = 47329
● = 47000 KJ per kg
Calculate its energy density?
● Less accurate due to greater heat losses
● More accurate due to smaller % uncertainty in
temperature change or mass of fuel burnt
Explain whether the accuracy in the student’s
calculated value for ΔcH may or may not be
improved by heating for longer.?
, C
● v=nRT/p
● 1x8.314x273/1 = 2269
● 1x8.314x293/1 = 2436
● 2436/2269= 1.07
A sample of gas, volume V, has its temperature
raised from 0°C to 20°C. The pressure remains
constant. What is the new volume? And method
how?
● B and based on several molecules
Don't say many/several compounds as 2023 MS said
ignore
Why are many bond enthalpies describes as
averages and Explain the meaning of average
in this context
DF.a - Formulae, equations and amount of substance | DF2 |
DF8 |
What is the equation linking mol (n), volume
of gas (dm3), and molar gas volume (24d
m3)?
What is 25cm3 equal to? 25g and 25ml
DF.Q Exam questions from past papers
Explain why the C=O double bond is shorter ● there are more electrons between the atoms in
than the C–O single bond (2) the double bond (1)
● giving greater attraction between the bonded
atoms (1)
● Comes from crops which can be regrown (1)
● Plants take in CO2 for photosynthesis (1) which
balances out roughly with CO2 produced on
burning (1)
Explain why biofuels are regarded as a
sustainable energy source and why they are
often describes as ‘carbon neutral’ (3)
When biodiesel burns it produces less carbon
monoxide than similar fuels made from crude Oxygen atom in structure allows more complete
oil. combustion therefore carbon dioxide produced (1) which
Explain why less carbon monoxide is produced is more fuel efficient (1) and this is desirable as CO is
and why this is desirable? toxic (1)
Compare
C2H5OH + 3O2 -> 2CO2 + 3H2O (ethanol)
C2H6 + 3.5O2 -> 2CO2 + 3H2O (ethane)
,Why can’t the enthalpy change for a thermal As thermal decomposition requires heat
decomposition reaction be measured directly?
NaHCO3 and Na2CO3 are ionic so not all bonds are
covalent (1)
Why can bond enthalpies not be used to
estimate ΔH1? (1)
2NaHCO3 (s) -> Na2CO3 (s) + CO2 (g) + H2O (l)
● Mr of C8H16 = 112
● Moles in one kg = 1000/112 = 8.93
● KJ per kg = 8.93 x 5300 = 47329
● = 47000 KJ per kg
Calculate its energy density?
● Less accurate due to greater heat losses
● More accurate due to smaller % uncertainty in
temperature change or mass of fuel burnt
Explain whether the accuracy in the student’s
calculated value for ΔcH may or may not be
improved by heating for longer.?
, C
● v=nRT/p
● 1x8.314x273/1 = 2269
● 1x8.314x293/1 = 2436
● 2436/2269= 1.07
A sample of gas, volume V, has its temperature
raised from 0°C to 20°C. The pressure remains
constant. What is the new volume? And method
how?
● B and based on several molecules
Don't say many/several compounds as 2023 MS said
ignore
Why are many bond enthalpies describes as
averages and Explain the meaning of average
in this context
DF.a - Formulae, equations and amount of substance | DF2 |
DF8 |
What is the equation linking mol (n), volume
of gas (dm3), and molar gas volume (24d
m3)?
What is 25cm3 equal to? 25g and 25ml
