Obtaining energy from fuels

Question 1

Gases

Define gas

Answer 1

The gas is a state of matter whereby the individual particles (wherever there may be single atoms or molecules) are widely spaced apart and are moving independently of one another

Question 2

Gases

Volume and pressure
The pressure in the vessel is equal ….

Answer 2

to the force of the gas on the wall of the vessel, per unit surface area with the standard unit being the Pascal (Pa)

Question 3

Gases

Volume and pressure
Where does the force come from?

Answer 3

Remember that the particles in the vessel are moving in random directions repeatedly coiling with the wall of the vessel and trying to push the vessel outwards

Question 4

Gases

Relationship between pressure temperature and amount and volume
At a given temperature and pressure …

Answer 4

the amount of gas molecules in a vessel is proportional to the volume of the vessel. This is known as Avogadro’s Law

Question 5

Gases

Relationship between pressure temperature and amount and volume
At the same temperature and pressure…

Answer 5

The amount of gas molecules in each vessel is the same

Question 6

Gases

Relationship between pressure temperature and amount and volume
The equation pV = nRT, stands for

Answer 6

P = pressure in kPa
V = volume in L
n = total amount of gas molecules (in mol) in the vessel 
R = universal gas constant in 8.31
T = temperature in Kelvin

Question 7

Gases

Standard molar volume
STP (standard temperature and pressure)

Answer 7

Temperature at 0°C (273 K) and a pressure of 1 bar (100kPa)

molar volume is 22.7 L mol-1

Question 8

Gases
____
°C °K
____

Answer 8

+ 273

-273

Question 9

Gases

Standard molar volume
SLC (standard laboratory conditions)

Answer 9

Temperature at 25°C (298 K) and a pressure of 1 bar (100kPa)

molar volume is 24.8 L mol-1

Question 10

Gases

Relationship between pressure temperature and amount and volume
Whats Boyle’s Law

Answer 10

Increasing the volume of the decreases the pressure inside the vessel expanding the volume of the particles spread out more and therefore collide less frequently with the sides of the vessel and vice versa

Question 11

Gases

Volume and pressure

mm —> kPa
Hg

Answer 11

/760 x 101.3

760 x 101.3 /

Question 12

Gases

Volume and pressure

Pa —> kPa

Answer 12

/1000

x1000

Question 13

Gases

Volume and pressure

atm —> kPa

Answer 13

/101.3

x101.3

Question 14

Gases

Volume and pressure

bar —> kPa

Answer 14

x100

/100

Question 15

Gases

Volume and pressure
–>
ug, mg, g, kg, t

Answer 15

/1000

x1000

Question 16

Energy profiles

Answer 16

The energy profile depicts the energy changes that occurs during a chemical reaction

Question 17

Energy profiles
Chemical energy (also known as enthalpy)

Answer 17

This is the energy contained within the various electric forces within and between species. The symbol for enthalpy is ΔH

Question 18

Energy profiles

Thermal energy

Answer 18

this is what we often think as heat. It is the kinetic energy that manifest in the speed of randomly moving particles. The higher the thermal energy contained within the set of molecules, the higher their speed and therefore the higher the temperature of the system

Question 19

Energy profiles

Kinetic energy

Answer 19

This is the umbrella term for energy contained within the movement of particles. Thermal energy is a type of kinetic energy

Question 20

Energy profiles

Steps that occur throughout the reaction

Answer 20

• The reactant particles move closer to one another
• The reactant particles move close enough to another for their electrons to start repelling one another, slowing the particle down. The kinetic energy for the particles is being converted into the chemical energy. Here the empathy starts to rise
• The reactant particles collide and the reactant bonds break. Breaking of bonds require energy to be ‘injected’ into the chemical. Hence the enthalpy continues to rise
• New bonds create the products. The formation of new bonds causes a decrease in chemical energy and conservation into kinetic energy. Hence the enthalpy will fall.

Question 21

Energy profiles

Draw exothermic and endothermic energy profile.

Answer 21

DO IT

Question 22

Energy profiles

Define activation energy

Answer 22

is the minimum energy needed to commence the reaction. It is discipline by EA on an energy profile and is sourced from the kinetic energy of the moving reactant particles

Question 23

Energy profiles
Define change in enthalpy
-
-

Answer 23

• If ΔH is positive. then this means that the reaction is endothermic, usually decreasing the temperature of the surroundings
• If ΔH is negative the reaction is exothermic. There has been an release of energy by the reaction is usually increasing the temperature of the surroundings

Question 24

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-

Answer 24

• If you want to multiply the coefficient of a reaction by x, then multiply ΔH by x
• If you want to add two equations together, add their ΔH values
• If you want to reverse the direction of a reaction, change the sign of the ΔH value