Developing Fuels

Question 1

What is the ideal gas equation and what units are needed?

Answer 1

PV=nRT

P-Pressure in Pa
V-Volume m^3
n-moles
R-Gas constant (data sheet)
T-temperature in K

Question 2

How do you convert from °c to °k?

Answer 2

Add 273

Question 3

How is a pi bond formed?

Answer 3

Sideways overlap of adjacent P orbitals above and below the internuvlear axis

Question 4

What is bond enthalpy?

Answer 4

The energy required to break one mole of the stated bond in gaseous state, under standard conditions

Question 5

What is the enthalpy change of reaction?

Answer 5

The enthalpy change when a certain amount of substance, in its standard state, reacts fully under standard conditions.

Question 6

What is the enthalpy change of formation?

Answer 6

The enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions.

Question 7

What is the enthalpy change of combustion?

Answer 7

The enthalpy change when one mole of substance is burned completely in oxygen under standard conditions

Question 8

What is the enthalpy change of neutralisation?

Answer 8

The enthalpy change when and acid and alkali react to form one mole of water under standard conditions.

Question 9

What equation links energy change to temperature change?

Answer 9

q=mc(delta)T

q=energy change (J)
m=mass (g)
c=specific heat capacity (J g-1 20°c-1)
Delta T= change in temperature (°c)

Question 10

What is specific heat capacity?

Answer 10

The energy required to raise 1g of substance by 1K without changing state

Question 11

What is Hess’s law?

Answer 11

Energy in a system must be conserved as it can not be created or destroyed. Therefore the overall enthalpy change for a reaction is the same, regardless of the route taken.

Question 12

What direction do the arrows point in a enthalpy change of formation Hess cycle?

Answer 12

upwards from C.

Question 13

What direction do the arrows point in a enthalpy change of combustion Hess cycle?

Answer 13

Downwards to C. C will always be water and carbon dioxide

Question 14

What are the stages of heterogeneous catalysts?

Answer 14

1) Reactants adsorb onto catalyst surface
2) Bonds in reactants weaken and break
3) New bonds start to form, producing a new molecule
4) Product desorbs

Question 15

What is a catalyst poison?

Answer 15

Something that adsorbs strongly onto the surface of the catalyst preventing it from working

Question 16

What is cracking?

Answer 16

The process by which long chain hydrocarbons are turned into shorter more useful hydrocarbons

Question 17

What is the test for alkenes?

Answer 17

Bromine water, alkenes will turn bromine water from orange-brown to colourless due to electrophilic addition occurring. Double bind opens up allowing bromine to bind to it

Question 18

What is an electrophile?

Answer 18

Electron acceptors that are attracted to areas of high electron density

Question 19

How can alkenes become alkanes?

Answer 19

Addition reaction with hydrogen with either:

Nickel catalyst, high temperature and pressure
Platinum catalyst, room temperature and pressure

Question 20

How can alkenes become alcohols?

Answer 20

Addition reaction with water, with either:

Conc. sulphuric acid catalyst then add water

Or

Steam, phosphoric acid catalyst and high temperature and pressure

Question 21

What is a stereoisomer?

Answer 21

Molecule which have the same structural formula but a different arrangement of atoms in space

Question 22

Why does E/Z isomerism occur?

Answer 22

The C=C restricts rotation
Two different groups on each C of the C=C

Question 23

What is fluorines appearance at RTP?

Answer 23

Pale yellow gas

Question 24

What is chlorine’s appearance at RTP?

Answer 24

Pale green gas

Question 25

What is bromines appearance at RTP?

Answer 25

Red/brown liquid

Question 26

What is iodine’s appearance at RTP?

Answer 26

Grey solid that sublimes into a purple vapour

Question 27

What is the trend regarding the volatility of the halogens?

Answer 27

Volatility decreases down the group as boiling point increases.

Question 28

What is the trend rgarding the reactivity of the halogens?

Answer 28

As the atomic radius increases it becomes harder for the halogen to gain an electron, as the positive attraction of the nucleus becomes weaker due to increased shielding. Therefore, reactivity decreases down the group.

Question 29

What is the basic halogen, halogen halide displacement trend?

Answer 29

A halogen will displace a halide ion from solution if the halide ion is bellow it in the periodic table.

Question 30

What happens when you add silver nitrate to chloride ions?

Answer 30

A white ppt forms (AgCl)

Question 31

What happens when you add silver nitrate to bromide ions?

Answer 31

A cream ppt forms (AgBr)

Question 32

What happens when you add silver nitrate to iodide ions?

Answer 32

A yellow ppt forms (AgI)

Question 33

Sometimes the ppt products from halide ions reacting with silver nitrate are hard to differentiate. How could you distinguish between them further?

Answer 33

Add dilute ammonia the silver chloride should dissolve and the solution will turn colourless. AgBr and AgI will not Add conc ammonia the silver bromide will dissolve and solution will turn colourless. AgI will not dissolve in any concentration of ammonia so the ppt will stay.

Question 34

How do you make hydrogen halides?

Answer 34

React a solid halide ion (NaF) with sulfuric acid to produce sodium hydrogen sulfate and hydrogen halide (HF) Which will be identified as misty fumes. However, this does not work with Br or I.

Question 35

What is the problem with trying to make HBr using H2SO4? How can this problem be avoided?

Answer 35

When you react NaBr and H2SO4 you make HBr and NaHSO4. However the HBr is very reactive so goes back to do a secondary reaction with H2SO4. This produces Br+ 2H2O+ SO2 (chocking gas) NaBr + H2SO4 ——> HBr + NaHSO4 HBr + H2SO4 ——> Br + 2H20 + SO2