Organic Chemistry Alkanes

Question 1

Organic compounds

Answer 1

Contains carbon and one or more other elements such as hydrogen, chlorine, oxygen or nitrogen

Question 2

Homologous series

Answer 2

A family of organic compounds with the same general formula and similar chemical properties

Alkanes, Alkenes, Alcohols, Carboxylic acids

They gradually change their physical properties as the number of carbon atoms per molecule increases

Question 3

Functional group

Answer 3

An atom or group of atoms that gives a molecule it’s characteristic properties

Question 4

Formulas of organic compounds

Answer 4

1. Empirical formula
2. Molecular formula
3. Structural formula

Question 5

Empirical formula

Answer 5

The simplest formula of a compound

Question 6

Molecular formula

Answer 6

Indicates the actual numbers of each kind of atom in a molecule of a substance

Question 7

Structural formula

Answer 7

Indicates how the atoms are bonded to each other within the molecule of a substance

Question 8

Bonds

Answer 8

Carbon 4 bonds
Hydrogen 1 bond
Oxygen 2 bonds

Question 9

Alkanes

Answer 9

A homologous series of hydrocarbons that contains only carbon-carbon single covalent bonds

Saturated

No functional groups

CnH2n+2

Question 10

Physical properties of alkanes

Answer 10

1. Low melting and boiling points
2. Insoluble in water
3. Soluble in organic solvents
   As it goes down the series:
4. Melting and boiling point increases
5. Becomes more viscous (density increases)
6. Becomes less flammable

Question 11

Why does the melting and boiling points of alkanes increases going down the series

Answer 11

The melting and boiling points of alkanes increases as their molecular sizes increase. This is because as the sizes of the alkane molecules increase, the forces of attraction between the molecules also increase

Question 12

Why does alkanes become more viscous as it goes down the series

Answer 12

Alkanes will become more viscous as their molecular sizes increase. This is due to the stronger forces of attraction between the alkane molecules

Question 13

Why does alkanes become less flammable going down the series

Answer 13

As the sizes of the alkane molecules increase, the percentage of carbon in the alkane molecules also increase

Question 14

Chemical properties of alkanes

Answer 14

1. Combustion

2. Substitution reaction

Question 15

Combustion

Answer 15

Exothermic reaction

alkane + oxygen —> carbon dioxide + water

Question 16

Substitution reaction

Answer 16

When an atom or group of atoms is replaced by another atom or group of atoms

Condition: Presence of ultraviolet light

Question 17

Use of alkanes

Answer 17

Fuels for aircrafts