alkanes

Question 1

what does organic mean?

Answer 1

compounds that are based on carbon, with other elements such as hydrogen, oxygen, and nitrogen

Question 2

what is a homologous series?

Answer 2

a group of chemicals/compounds with the same general formula, a pattern of physical properties, and similar chemical properties

Question 3

what are hydrocarbons?

Answer 3

compounds consisting of only hydrogen and carbon

Question 4

what are alkanes?

Answer 4

hydrocarbons with only single bonds

Question 5

describe the naming system

Answer 5

root: based on the number of C atoms
suffix: homologous series
prefix: additional atoms

Question 6

what is the structural formula of ethane?

Answer 6

(CH3)2

Question 7

what is the structural formula of propane?

Answer 7

CH3CH2CH3

Question 8

what is the structural formula of butane?

Answer 8

CH3CH2CH2CH3

OR

CH3(CH2)2CH3

Question 9

What are the physical properties of alkanes (same as covalent discrete)?

Answer 9

Since they are covalent discrete:

• low melting point
• insulator
• soluble in oils, insoluble in water

Question 10

describe the mpt/bpt of alkanes

Answer 10

mpt/bpt: from small molecules –> large molecules, INCREASES due to more IMFs

Question 11

describe the viscosity of alkanes

Answer 11

viscosity: from small molecules –> large molecules, INCREASES due to more IMFs and larger molecules intertwine, like noodles

Question 12

describe the volatility of alkanes

Answer 12

volatility: from small molecules –> large molecules, DECREASES due to increasing bpt

Question 13

describe the colour of alkanes

Answer 13

colour: small molecules –> large molecules, COLOURLES-YELLOW-BLACK

Question 14

what is viscosity?

Answer 14

resistance to liquid flow

Question 15

what is volatility?

Answer 15

ease of turning into a gas

Question 16

are alkanes generally unreactive or reactive and why?

Answer 16

generally unreactive, due to containing strong single bonds

Question 17

what does saturated mean?

Answer 17

chemical only containing strong single bonds

Question 18

how can we make alkanes react through energy?

Answer 18

in the form of:

• heat
• electricity
• light

Question 19

IMPORTANT - what are the three types of reactions alkanes undergo?

Answer 19

ALKANES:

• SUBSTITUTION
• COMBUSTION
• DECOMPOSITION

Question 20

what is the general equation for the combustion of alkanes?

Answer 20

Alkane + oxygen → carbon dioxide + water

Question 21

what is the symbol equation for the combustion of methane?

Answer 21

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

Question 22

what is the symbol equation for the combustion of ethane?

Answer 22

C2H6 (g) + 3½O2 (g) → 2CO2 (g) + 3H2O (l)

Question 23

what is the symbol equation for the combustion of propane?

Answer 23

C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (l)

Question 24

what is the symbol equation for the combustion of butane?

Answer 24

C4H10 (g) + 6½O2 (g) → 4CO2 (g) + 5H2O (l)

Question 25

what happens in the substitution of alkanes?

Answer 25

one atom (or group of atoms) is swapped with another atom (or group of atoms)

Question 26

what needs to be present for alkanes to undergo substitution?

Answer 26

ultraviolet radiation (sunlight is a source of UV radiation) - this is the ACTIVATION ENERGY

Question 27

does only one hydrogen atom always get substituted?

Answer 27

no, more than one hydrogen atom can be substituted depending on the amount of ultraviolet radiation there is

Question 28

what is the general word equation for the substitution of alkanes with halogens?

Answer 28

alkane + halogen → halo alkane + hydrogen halide

Question 29

what type of reaction is this, and what will it make? ethane + chlorine

Answer 29

substitution of alkanes with halogens chloroethane and hydrogen chloride

Question 30

what type of reaction is this, and what will it make? methane + bromine

Answer 30

substitution of alkanes with halogens bromomethane + hydrogen bromide

Question 31

what type of reaction is this, and what will it make? propane + fluorine

Answer 31

substitution of alkanes with halogens option 1: 1-fluoropropane option 2: 2-fluoropropane and hydrogen fluoride

Question 32

how can we test which isomer we have if multiple can be made through a reaction?

Answer 32

using fractional distillation

Question 33

what do we do if we have multiple prefixes in a name?

Answer 33

arrange them alphabetically, ignoring "di", "tri", "tetra", etc.

Question 34

what is complete combustion?

Answer 34

when there is excess/enough oxygen in a combustion reaction with an alkane carbon dioxide and water are made from an alkane and oxygen

Question 35

what is incomplete combustion?

Answer 35

when there is not enough oxygen during a combustion with alkane + oxygen instead of carbon dioxide, it makes carbon monoxide and water, and soot

Question 36

how do we avoid incomplete combustion?

Answer 36

by ventilation

Question 37

why is soot bad?

Answer 37

it damages lungs, and damages machinery

Question 38

what is cracking?

Answer 38

decomposition - breaking a large alkane into a smaller alkane and an alkene

Question 39

what happens when we heat an alkane?

Answer 39

it decomposes to make a smaller alkane and an alkene

Question 40

what conditions are needed for the decomposition of an alkane?

Answer 40

- approximately 300 degrees of heat - a catalyst of Al2O3 or SiO2