Combustion Of Alkanes

Question 1

What is a fuel?

Answer 1

• something that can be used to produce useful energy

Question 2

What is the complete combustion of alkanes?

Answer 2

• alkane reacts with a plentiful supply of oxygen to give CO2 and water, releasing energy
• so alkanes can be used as a fuel as it produces useful energy, esp short alkanes

Question 3

Give the equation for the complete combustion of methane

Answer 3

CH4 (g) + 2O2 (g) = CO2 (g) + 2H2O (l)

Question 4

Describe the incomplete combustion for alkanes

Answer 4

• in a limited supply of oxygen, incomplete combustion may occur
• producing carbon monoxide gas or solid carbon along with water

Question 5

Give the equations for the incomplete combustion of methane

Answer 5

Carbon monoxide : CH4 (g) + 1.5 O2 (g) = CO (g) + 2H2O (l)
Carbon (s) : CH4 (g) + O2 (g) = C(s) + 2H2O (l)

Question 6

What affects strength of induced dipole dipole IMF?

Answer 6

• strength of induced dipole dipole IMF depends on number of electrons in atom or molecule
• the larger number of electrons, the stronger induced dipole dipole IMF

Question 7

What makes IMF stronger?

Answer 7

• number of electrons increasing

Question 8

Describe what IMF alkanes have and why?

Answer 8

• alkanes only have induced dipole dipole IMF
• not hydrogen bonding as N, O, and F arent present (only C,H)
• not permanent dipole as theres no sig difference in electronegativity

Question 9

What factor affects bp of alkanes?

Answer 9

• change of shape = surface area

Question 10

Why does change of shape affect bp of alkanes?

Answer 10

• when S.A decreases, number of electrons stays the same
• bp decreases
• coz theres less surface contact
• weaker induced dipole dipole IMF

Question 11

What are two uses of methane?

Answer 11

• methane is widely used for heating + cooking

Question 12

State the conditions of the free radical polymerisation of alkanes

Answer 12

• An addition reaction
• conditions: 200 c
• high pressure (2000 atm)