Organic Chemistry Nov 2018

Question 1

What is crude oil?

Answer 1

Crude oil is a fossil fuel that is found underground in rocks. It has formed over millions of years by sea creatures (mainly plankton) being squashed and buried in mud.

Question 2

What are alkanes?

Answer 2

Alkanes are a homologous series of saturated hydrocarbons with a general formula of CnH2n+2.

Question 3

What is a hydrocarbon?

Answer 3

A molecule made up of only hydrogen and carbon.

Question 4

What does it mean by saturated?

Answer 4

It is a molecule that contains only single covalent bonds.

Question 5

What is a homologous series?

Answer 5

A family of compounds with the same general formula, the same functional group and similar chemical properties.

Question 6

What is the displayed formula?

Answer 6

A drawing of a molecule showing all atoms and bonds.

Question 7

What is a fraction?

Answer 7

A mixture of molecules with similar boiling points.

Question 8

What is fractional distillation?

Answer 8

A method used to separate miscible liquids with different boiling points.

Question 9

What is a fractionating column?

Answer 9

The apparatus used is the process of fractional distillation.

Question 10

What are the 4 alkanes you need to know?

Answer 10

Methane, Ethane, Propane, Butane

Meth = 1 carbon, Eth = 2 carbons, Prop = 3 Carbons, But = 4 carbons

Question 11

How does fractional distillation work?

Answer 11

Crude oil enters a fractionating column at the bottom. It is then heated. The alkanes found in crude oil are all different lengths which means they have different boiling points. Due to the fractionating column decreasing in temperature the higher it goes, smaller alkanes with lower boiling points condense further up with larger alkanes condensing lower down and some not boiling at all and forming bitumen at the bottom.

Question 12

What are the properties of alkanes?

Answer 12

Long alkanes - High boiling points, Viscous, Hard to
ignite & Burn with a smoky flame.
Short alkanes - Low boiling points, Runny, Easy to ignite
& Burn with a clean flame.

Question 13

What is complete combustion? Incomplete combustion?

Answer 13

Complete combustion - When a substance burn with a
good supply of oxygen.
Incomplete combustion - When a substance burns with
a poor supply of oxygen.

Question 14

What is cracking?

Answer 14

The thermal decomposition of long alkanes into shorter alkanes and alkenes.

Question 15

What is an alkene?

Answer 15

A homologous series of unsaturated hydrocarbons with the general formula CnH2n.

Question 16

What does it mean by unsaturated?

Answer 16

A molecule that contains one or more double covalent bonds.

Question 17

What are the 4 alkenes you need to know?

Answer 17

Ethene, Propene, Butene, Pentene

Eth = 2 carbons, Prop = 3 Carbons, But = 4 carbons, Pent = 5 carbons

Question 18

What is the functional group in alkenes?

Answer 18

C = C (= is double covalent bond)
Functional group - Atom or group of atoms responsible
for most of the chemical reactions of
a compound.

Question 19

What is an addition reaction?

Answer 19

A reaction in which atoms bond to the atoms in a C = C double bond to form a saturated molecule.

Question 20

What is hydrogenation? Hydration?

Answer 20

Hydrogenation - Addition of hydrogen

Hydration - Addition of water

Question 21

Why are alkenes very valuable?

Answer 21

Alkenes can be used to polymers or they can be used as a starting material for many other chemicals.

Question 22

Why do you not normally burn alkanes in oxygen?

Answer 22

They burn with a smoky flame due to incomplete combustion.