Organic Chemistry Part 1.1

Question 1

All organic compounds contain carbon and hydrogen (T/F)

Answer 1

F. All organic compounds contain carbon. MOST contain hydrogen.

Question 2

What are hydrocarbons?

Answer 2

Contain only carbon and hydrogen

Question 3

What is the homologous series?

Answer 3

A family of compounds with same functional group and similar chemical properties

Question 4

What is a functional group?

Answer 4

An atom or a group of atoms that give a molecule its characteristic chemical properties

Question 5

Why do organic compounds in the same homologous series have similar chemical properties?

Answer 5

Same functional group

Question 6

Does the general formula of organic compounds apply if there is more than 1 functional group present in the organic compound?

Answer 6

No

Question 7

General characteristics of a homologous series (Name 4)

Answer 7

-Same general formula
-Similar chemical properties
-Gradual change in their physical properties down the series
-Successive members in homologous series differ from each other by 1 -CH2- group (Mr 14.0)

Question 8

Trend of boiling and melting points down the homologous series

Answer 8

Increases, with increased RELATIVE MOLECULAR MASS, MORE energy to overcome STRONGER intermolecular forces of attraction between LARGER molecules

Question 9

Trend of Viscosity down the homologous series

Answer 9

More viscous, with increased RELATIVE MOLECULAR MASS, flow less easily, due to STRONGER intermolecular forces of attraction between LARGER molecules

Question 10

How many bonds present between carbon atoms in saturated and unsaturated compounds

Answer 10

Saturated: Single bond
Unsaturated: At least double or triple bonds

Question 11

Describe briefly what is natural gas(colour, smell, contain what)

Answer 11

A colourless and odourless gas

Question 11

Name the first 6 prefixes and 4 suffixes for naming of organic compounds

Answer 11

Meth, Eth, Prop, But, Pent, Hex
-ane, -ene, -ol, -olic acid

Question 12

Describe briefly what is crude oil (colour, smell, contain what)

Answer 12

A dark-brown, foul-smelling liquid containing naturally occurring mixture of hydrocarbons

Question 13

Describe briefly what is natural gas (colour, smell, made up of what)

Answer 13

Colourless and odourless gas. Made up of methane and other short chain alkanes

Question 14

Why is natural gas the ‘cleanest fossil fuel’?

Answer 14

Lowest percentage of carbon by mass. CH4 main component in natural gas, 75% carbon.

Question 15

Why is liquified natural gas safe for consumers compared to gaseous fuels

Answer 15

Does not burn too easily, safer for consumers

Question 16

How are crude oil and natural gas formed?

Answer 16

From the remains of marine creatures and plants, sinking to the seabed when they die.

They are subjected to heat from earth and pressure, forming natural gas and crude oil

Question 17

What is crude oil separated into in an Oil Refinery and what does each fraction contain?

Answer 17

Crude oil can be separated into useful fractions by fractional distillation.

Each fraction is a mixture of hydrocarbons which boil over a certain range of temperatures.

Question 18

Difference between lighter and heavier fractions

Answer 18

Lighter contains molecules with fewer carbon atoms, thus having a lower boiling point range

Question 19

Lighter Fractions come out at the higher “outlets” of the fractional columns (T/F)

Answer 19

True

Question 20

DESCRIBE in detail how does the fractional distillation of crude oil work

Answer 20

1) Crude oil heated in a furnace of about 400 degrees Celsius. Boiling takes place

2) Vapours are passed into fractionating column. Fractionating column hottest at the bottom and gets cooler at the top.

3) Hot vapour rise up the column, cools, condenses at different heights and collected at respective outlets.

4) Lighter Fractions with lower boiling points are collected at the top of the column as GASES.

5) Heavier Fractions with higher boiling points collected at the bottom of the column as RESIDUE.

Question 21

Describe the process of catalytic cracking and the necessary conditions for it to occur

Answer 21

Cracking is a process to break down long-chain hydrocarbons into shorter-chain hydrocarbons by passing the hot vapourised hydrocarbons over a HEATED catalyst.

Conditions: 500-700 degrees Celsius aluminium oxide and silicon dioxide. Pressure about 1atm.

Question 22

What are the products of cracking long chain alkanes (Always produced, most of the times, sometimes)

Answer 22

Always: Smaller molecules of alkenes

Most: Smaller molecules of alkanes

Sometimes: Hydrogen

Question 23

What are the importance of cracking?

Answer 23

Convert heavy crude oil fractions into lighter fractions which are low in supply, high in demand

Produce large amount of short chain alkenes which are used to make plastics, and other useful materials

Produce hydrogen, used in manufacture of ammonia in the Haber Process

Question 24

What is biofuel and where does it come from

Answer 24

An alternative renewable energy source to crude oil and natural gas.

Comes from plants/animals, replaced relatively quickly

Question 25

Why is biofuels compared to fossil fuels more environmentally sustainable in terms of carbon dioxide emission

Answer 25

Using bioethanol as example, sugarcane plant can absorb co2 through photosynthesis, offsetting the co2 produced when bioethanol is burnt