U3AOS1 - Obtaining Energy from Fuels

Question 1

What is a Fuel

Answer 1

Substance that contains chemical energy, stored in bonds, which is released through a combustion reaction, producing heat or power

Question 2

What is a renewable fuel

Answer 2

fuels that can be replenished at or greater than the rate of consumption

Question 3

Origins of Fossil Fuels

Answer 3

Formed from the decomposition of plant and animal matter over a very long time

Question 4

Renewability of Fossil Fuels

Answer 4

Considered Non Renewable - as the process of decomposition cannot be increased to match consumption levels (it proceeds at a constant rate)

Question 5

Origin of Biofuels

Answer 5

Produced from organic matter such as corn and sugarcane

Question 6

Renewability of Biofuels

Answer 6

Considered Renewable - as the organic matter can be grown at the required rate to match consumption

Question 7

Specific Heat Capacity (including the units)

Answer 7

the heat required to raise the temperature of one gram of a substance by 1 degree Celsius

Commonly expressed as J g-1 °C-1

Question 8

Specific Heat Capacity Formula

Answer 8

Question 9

How does bonding influence specific heat capacity

Answer 9

stronger bonds means that more energy can be stored, and thus will result in a higher specific heat capacity

Question 10

What is ΔH (Change in Enthalpy)

Answer 10

Refers to the change in energy during the course of the reaction

Question 11

Endothermic Reaction

Answer 11

Reactions where energy is gained/absorbed over the course of the reaction

Positive Change in Enthalpy

Question 12

Exothermic Reaction

Answer 12

Reactions where energy is lost/released over the course of the reaction

Negative Change in Enthalpy

Question 13

Heat of Combustion

Answer 13

amount of energy released during a combustion reaction

Often a positive value (representing a magnitude) - but represents a negative Change in Enthalpy

Question 14

Converting kJ/mol to kJ/g

Answer 14

Check this is right - divide the kJ/mol by the molar mass

Question 15

Thermochemical Equation

Answer 15

balanced equations, including states and the ΔH value for the equation

Question 16

Calculating the ΔH for a particular thermochemical equation

Answer 16

ΔH = Molar Constant for Fuel in Equation * ΔHc (from databook)

Important that unit is included

Question 17

What impact does reversing the equation have on ΔH

Answer 17

Changes the sign of the ΔH

Question 18

Combustion Reactions (inc exo/endo)

Answer 18

chemical reaction between a fuel and a oxygen

They’re exothermic reactions (negative ΔH), as energy is released during the reaction as heat

Question 19

Complete Combustion

Answer 19

Occurs when oxygen is the excess reagent

Products are CO2 and H2O

Question 20

Incomplete Combustion

Answer 20

Occurs when oxygen is the limiting reagent

Products are CO and H2O
(CO is the same as soot)

Question 21

What is a gas

Answer 21

State of matter with no fixed shape or volume, and which fills the available space

Question 22

What is Gas Pressure (inc generic formula)

Answer 22

The force a gas exerts on the walls of its container

Pressure = Force/Area

Question 23

Pressure units Nm^-2 are equivalent to?

Answer 23

Pascal (Pa)

Question 24

How to convert Celsius -> Kelvin

Answer 24

-273

Question 25

How to convert Kelvin -> Celsius

Answer 25

+273

Question 26

Standard Lab Conditions

Answer 26

25 Degrees Celsius
100kPa
1M Solution

Question 27

Universal Gas Law

Answer 27

Question 28

Relationship between Moles & Volume of Gases at SLC

Answer 28

Question 29

Hess Law

Answer 29

The total enthalpy change during the complete course of a chemical reaction is independent of the sequence of steps taken