Developing Fuels

Question 1

What is the ideal gas equation

Answer 1

pV = nRT
p = pressure in Pa
V = volume in m3
n = number of moles, in mol
R = gas constant (8.314)
T = temp in Kelvin

Question 2

What is the difference between a π bond and a σ bond

Answer 2

σ bonds are cause by direct/head on overlaps between p or s orbitals

π bonds are caused by indirect/side on overlaps between p orbitals

Question 3

What is a double bond

Answer 3

Both a π bond and a σ bond

Question 4

What does endothermic mean

Answer 4

Reactions that take in energy from surroundings
Energy to break bonds is greater than energy formed in making bonds

Question 5

What does exothermic mean

Answer 5

Release energy to surroundings
Energy made from forming bonds is greater then energy made from breaking bonds

Question 6

What are standard conditions

Answer 6

RTP - room temp - 298K
100 kPa pressure, or 1 atm
All solutions at 1 mol dm-3 for electrode potentials

Question 7

At what temperature will 1.28g of chlorine gas occupy 98.6dm^3, at a pressure of 175 Pa?

Answer 7

1.28 / (35.5 x 2) = 0.0180 mol
175 x 0.0986 / 0.0180 x 8.314 =
115 K

Question 8

Define average bond enthalpy

Answer 8

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

Question 9

Explain why the bond enthalpy of C=O in ketones is greater than the bond enthalpy of C-O in alcohols

Answer 9

C=O bond is made of a π bond and a σ bond, meaning there are 4 shared electrons, where C-O only has 2. The greater electron density between the positive nuclei in the double bond causes a stronger attraction to the shared electrons, therefore a stronger bond and greater bond enthalpy

Question 10

Define ΔrHθ

Answer 10

Standard enthalpy change of reaction - enthalpy change when a reaction occurs in its mole ratios stated, under standard conditions

Question 11

Define ΔfHθ

Answer 11

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

Question 12

Define ΔcHθ

Answer 12

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

Question 13

Define a catalyst

Answer 13

A species that speeds up the rate of a reaction by creating an alternate pathway that has a lower activation energy, and is not used up during the reaction

Question 14

Define a catalyst poison

Answer 14

A substance that reduces catalyst effectiveness by permanently bonding to the active sites

Question 15

Define heterogeneous

Answer 15

The catalyst is not in the same phase as reactants

Question 16

Explain how reactions happen on heterogeneous catalysts

Answer 16

Reactant adsorbs to catalyst surface
Bonds in the reactant break
New bonds in reactants form to create new product
Product desorbs from catalyst surface and diffuses away

Question 17

What is cracking

Answer 17

Breaking long chain alkanes into shorter chain alkanes and alkenes

Question 18

Name some common simple molecular pollutants

Answer 18

NOx, CO, CO2, SOx, unburnt hydrocarbons