ORGANIC CHEMISTRY

Question 1

what is the definition of a hydrocarbon?

Answer 1

a hydrocarbon is a compound that is formed of only hydrogen and carbon atoms

Question 2

what is an alkane?

Answer 2

an alkane is the simplest form of hydrocarbon that you can get

Question 3

what is the formula for an alkane

Answer 3

CnH2n+2

Question 4

alkanes are saturated compounds, what does this mean?

Answer 4

each atom has 4 single covalent bonds

Question 5

what are the first 4 alkanes?

Answer 5

methane, ethane, propane, butane

CH4. C2H6. C3H8 C4H10

Question 6

the shorter the hydrocarbon, _______

Answer 6

👩‍🔬the less viscous (runnier)
👩‍🔬more volatile (they have lower boiling points)
👩‍🔬more flammable

Question 7

what is the equation for complete combustion with hydrocarbons?

Answer 7

hydrocarbon + oxygen - carbon dioxide + water (+energy)

Question 8

what happens to both hydrogen and carbon atoms during combustion?

Answer 8

they both oxidise ( in this case they gain oxygen)

Question 9

what is crude oil?

Answer 9

crude oil is a fossil fuel

Question 10

how is crude oil made?

Answer 10

crude oil is made over millions of years. it is formed by the remains of dead plants and animals, mainly plankton, that were buried in the mud. over millions of years, high temperatures and pressure turned it into crude oil.

Question 11

how do you separate hydrocarbons fractions?

Answer 11

fractional distillation.

Question 12

how does fraction distillation of hydrocarbons work?

Answer 12

🌡the oil is heated until it is turned into gas. the gasses enter a fractioning column
🌡in the column, there are temperature gradients, it is the hottest at the bottom and less hot as you go up
🌡the longer hydrocarbons have a higher boiling point, so they are condensed into liquids and drained out at an early stage (when they are near the bottom)
🌡the smaller chained hydrocarbons have a lower melting point, so they rise to the top of the column.

Question 13

what is cracking?

Answer 13

cracking is when larger hydrocarbon molecules are broken down into smaller ones

Question 14

what are the two ways of cracking?

Answer 14

👉🏻 steam cracking, by heating a mixture of hydrocarbons and steam to a very high temperature
👉🏻catalystic cracking, by passing hydrocarbon vapours over a hot catalyst

Question 15

what other compound is formed when cracking?

Answer 15

alkenes which are unsaturated hydrocarbons

Question 16

what are alkenes?

Answer 16

alkenes have a double bond between two carbon atoms making them more reactive than alkanes