chap 2- developing fuels

Question 1

what is the volume of one mole of gas at room temp and pressure

Answer 1

24dm^3

Question 2

what is room temp and pressure

Answer 2

298K and 100kPa

Question 3

what is the formula for working out the number of moles in a volume of gas at RTP

Answer 3

no of moles = volume (dm3) / 24 or

volume in cm3 / 24,000

Question 4

what is the ideal gas equation

Answer 4

PV = nRT
pressure (Pa)
volume (m3)
R= 8.314 JK-1 mol -1
temperature (K)

Question 5

how can you use a gas syringe to measure gas volume

Answer 5

attach gas syringe to opening of reaction vessel and it’ll show the total volume of gas produced in a reaction. Doesn’t show the difference between different gases

Question 6

what types of reactions are bond making and bond breaking

Answer 6

bond making is exothermic as energy is released when bonds are formed
bond breaking is endothermic as you require an input of energy to break a bond

Question 7

what is average bond enthalpy

Answer 7

the energy needed to break one mole of bonds in the gas phase, averaged over many different compounds

Question 8

why does a double bond have a greater bond enthalpy than a single bond between the same elements

Answer 8

it is a shorter bond and electron density is greater as more electrons are shared but in a smaller area

Question 9

what is standard enthalpy change of reaction

Answer 9

the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation under standard conditions

Question 10

what is standard enthalpy change of formation

Answer 10

the enthalpy change when one mole of a compound is formed from its elements in their standard states, under standard conditions

Question 11

what is standard enthalpy change of combustion

Answer 11

the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions

Question 12

what is hess’ law

Answer 12

the total enthalpy change of a reaction is always the same regardless of the route taken

Question 13

how do you find enthalpy change using a calorimeter

Answer 13

burn a flammable liquid (fuel) that will heat the water and if you know the mass, temp change and specific heat capacity of the water you can work out heat absorbed

Question 14

how do you work out enthalpy change of neutralisation using a calorimeter

Answer 14

add a known volume of acid to an insulated container and measure the temp
add known vol of alkali and record temp rise while stirring
use Q=mc delta T to work out the heat needed to raise the temp of the solution formed

Question 15

define a catalyst

Answer 15

a catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. It is chemically unchanged at the end of the reaction

Question 16

define catalysis

Answer 16

speeding up a chemical reaction by using a catalyst

Question 17

what is a heterogeneous catalys

Answer 17

a catalyst thats in a different physical state to the reactants

Question 18

how does a reaction happen on a solid heterogeneous catalyst

Answer 18

reactant molecules arrive at the surface and bond with the solid catalyst (adsorption)
the bonds between the reactants atoms are weakened and break up this forms radicals. the radicals get together and make up new molecules
the new molecules detatch from the catalyst

Question 19

what are radicals

Answer 19

atoms or molecules with unpaired electrons

Question 20

what happens if a catalyst is poisoned

Answer 20

they no longer work. the poison clings to the catalysts surface more strongly than the reactant does. so the catalyst can’t get involved in the reaction

Question 21

what are cycloalkanes

Answer 21

saturated hydrocarbons with a ring of carbon atoms. general formula CnH2n

Question 22

what is benzene

Answer 22

(C6H6) a cyclic alkene with 6 carbons and 3 double bonds. the double bond electrons are delocalised around the carbon ring

Question 23

what is the difference between aliphatic compounds and aromatic compounds

Answer 23

aromatic compounds are also called arenes and have a benzene ring structure
aliphatic compounds are all other organic compounds eg alkanes and alkenes

Question 24

what is the general formula for alcohols

Answer 24

CnH2n+1OH

Question 25

what is a sigma bond

Answer 25

formed when 2 orbitals overlap in a straight line giving the highest possible electron density between the 2 positive nuclei so sigma bonds are usually very strong

Question 26

what is a pi bond

Answer 26

formed when 2 p orbitals overlap sideways. weaker than a sigma bond

Question 27

what is a double bond always made up of

Answer 27

a sigma bond and a pi bond

Question 28

what is a stereoisomer

Answer 28

have the same shortened structural formula but a different arrangement in space

Question 29

what is an electrophile

Answer 29

electron pair acceptors. attracted to places where there are lots of electrons

Question 30

why does electrophilic addition happen

Answer 30

because the double bond has got plenty of electrons and so can be attacked by electrophiles

Question 31

how is ethanol made

Answer 31

by hydrating ethene with steam at 300c and 60atm in the presence of phosphoric (v) catalyst

Question 32

when are oxides of nitrogen produced

Answer 32

when the high pressure and temperature in a car engine cause the nitrogen and oxygen in the air to react together

Question 33

what happens to unburnt fuel molecules from an engine

Answer 33

they come out as unburnt hydrocarbons

Question 34

how is ground level ozone produced

Answer 34

when unburnt hydrocarbons and oxides of nitrogen react in the presence of sunlight

Question 35

what is photochemical smog

Answer 35

made up partly by ground level ozone. it can irritate eyes, aggravate respiratory problems and cause lung damage

Question 36

what are particulates

Answer 36

tiny particles of liquid suspended in the air
can settle in the lungs and cause decreased lung function and airway irritation also contribute to cardiovascular problems