Chapter Two : Energy calculations

Question 1

Enthalpy definition (heat content)

Answer 1

The total energy stored in a substance (H)

Question 2

Change in enthalpy (heat of reaction)

Answer 2

Change in heat content when a substance undergoes a chemical reaction and the energy of the reactants is different to the energy of the products
Delta H

Question 3

Change in heat content equation

Answer 3

Change in heat content = (heat content of products) - (heat content of reactants)

Question 4

Standard laboratory conditions

Answer 4

25 degrees
1 mole of the substance
1M solutions
Heat absorbed or released is in kJ
Pressure is 100kPa

Question 5

Heat of solution definition

Answer 5

Is the change in enthalpy when 1 mole of any substance dissolves in water

Question 6

Heat of neutralisation definition

Answer 6

Is the change in enthalpy when an acid reacts with a base to form 1 mole of water

Question 7

Heat of vapourisation definition

Answer 7

Is the change in enthalpy when 1 mole of liquid is converted to gas

Question 8

Heat of combustion definition

Answer 8

Is the enthalpy change when a substance burns in air, always exothermic

Question 9

Exothermic reaction facts

Answer 9

When heat is released
Heat content of reactants is greater than products
Bonds in products are stronger than bonds in reactants
Neg delta H value

Question 10

Endothermic reaction facts

Answer 10

When heat is absorbed
Heat content of products is greater than reactants
Bonds in reactants are stronger than the bonds in products
Pos delta H value

Question 11

Kinetic Molecular Theory of Gases

Answer 11

Gases are made up of particles moving constantly and at random.
Gas particles are very far apart, and the volume of the particles is very small compared with the volume that the gas occupies.
The forces of attraction and repulsion between gas particles are zero.
Gas particles collide with each other and the walls of their container, exerting pressure.
The higher the temperature, the faster the gas particles move, increased kinetic energy.

Question 12

Kinetic Molecular theory statement

Answer 12

Matter is made up of continuously moving particles

Question 13

Gas Pressure definition

Answer 13

Particles exert a force by colliding with the walls of a container. Each tiny collision adds to all the others to make up the continuous force

Question 14

Pressure equation

Answer 14

Pressure = Force / Area

Question 15

Unit of measurement of pressure

Answer 15

Pascals

1 kPa = 1000 Pa

Question 16

Unit of temperature

Answer 16

Kalvin

Question 17

Temperature (c to K)

Answer 17

K = c + 273

Question 18

Volume of gas conversions

Answer 18

1 m^3=10^3 L=10^6 mL

Question 19

Boyle’s Law

Answer 19

Pressure is inversely proportional to volume

P1V1=P2V2

Question 20

Charles Law

Answer 20

Volume is proportional to temperature

V1/T1 = V2/T2

Question 21

Combined Gas equation

Answer 21

P1V1/T1=P2V2/T2

Question 22

Molar Gas Volume Theory

Answer 22

Equal volumes of all gases measured at the same temperature and pressure contain the same number of particles

Question 23

Molar Gas Volume Value

Answer 23

1 mole of any gas at SLC occupies a volume of 24.8 L

Question 24

Formula for mol of Gases

Answer 24

n = V/Vm
V is in L
Vm is 24.8L/mol

Question 25

Universal gas equation

Answer 25

PV=nRT
P=pressure
V= volume in L
n= mol
R=8.31JK^-1mol^-1

Question 26

Mass conversions

Answer 26

1 tonne = 1000kg = 1000000g

Question 27

Calculating greenhouse gases from 1 MJ of energy

Answer 27

1. If the mole of the fuel produces a particular amount of kJ, convert MJ to kJ and cross multiply to find mole
2. Work out ratio between fuel and greenhouse gas (CO2), and find mol for CO2
3. Use n=V/Vm to work out volume of CO2
   or use n=mXM to work out grams