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alkanes Flashcards

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1
Q

what does organic mean?

A

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

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2
Q

what is a homologous series?

A

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

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3
Q

what are hydrocarbons?

A

compounds consisting of only hydrogen and carbon

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4
Q

what are alkanes?

A

hydrocarbons with only single bonds

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5
Q

describe the naming system

A

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

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6
Q

what is the structural formula of ethane?

A

(CH3)2

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7
Q

what is the structural formula of propane?

A

CH3CH2CH3

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8
Q

what is the structural formula of butane?

A

CH3CH2CH2CH3

OR

CH3(CH2)2CH3

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9
Q

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

A

Since they are covalent discrete:

  • low melting point
  • insulator
  • soluble in oils, insoluble in water
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10
Q

describe the mpt/bpt of alkanes

A

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

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11
Q

describe the viscosity of alkanes

A

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

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12
Q

describe the volatility of alkanes

A

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

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13
Q

describe the colour of alkanes

A

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

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14
Q

what is viscosity?

A

resistance to liquid flow

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15
Q

what is volatility?

A

ease of turning into a gas

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16
Q

are alkanes generally unreactive or reactive and why?

A

generally unreactive, due to containing strong single bonds

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17
Q

what does saturated mean?

A

chemical only containing strong single bonds

18
Q

how can we make alkanes react through energy?

A

in the form of:

  • heat
  • electricity
  • light
19
Q

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

A

ALKANES:

  • SUBSTITUTION
  • COMBUSTION
  • DECOMPOSITION
20
Q

what is the general equation for the combustion of alkanes?

A

Alkane + oxygen → carbon dioxide + water

21
Q

what is the symbol equation for the combustion of methane?

A

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

22
Q

what is the symbol equation for the combustion of ethane?

A

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

23
Q

what is the symbol equation for the combustion of propane?

A

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

24
Q

what is the symbol equation for the combustion of butane?

A

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

25
Q

what happens in the substitution of alkanes?

A

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

26
Q

what needs to be present for alkanes to undergo substitution?

A

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

27
Q

does only one hydrogen atom always get substituted?

A

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

28
Q

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

A

alkane + halogen → halo alkane + hydrogen halide

29
Q

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

ethane + chlorine

A

substitution of alkanes with halogens

chloroethane and hydrogen chloride

30
Q

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

methane + bromine

A

substitution of alkanes with halogens

bromomethane + hydrogen bromide

31
Q

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

propane + fluorine

A

substitution of alkanes with halogens

option 1: 1-fluoropropane

option 2: 2-fluoropropane

and hydrogen fluoride

32
Q

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

A

using fractional distillation

33
Q

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

A

arrange them alphabetically, ignoring “di”, “tri”, “tetra”, etc.

34
Q

what is complete combustion?

A

when there is excess/enough oxygen in a combustion reaction with an alkane

carbon dioxide and water are made from an alkane and oxygen

35
Q

what is incomplete combustion?

A

when there is not enough oxygen during a combustion with alkane + oxygen

instead of carbon dioxide, it makes carbon monoxide and water, and soot

36
Q

how do we avoid incomplete combustion?

A

by ventilation

37
Q

why is soot bad?

A

it damages lungs, and damages machinery

38
Q

what is cracking?

A

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

39
Q

what happens when we heat an alkane?

A

it decomposes to make a smaller alkane and an alkene

40
Q

what conditions are needed for the decomposition of an alkane?

A
  • approximately 300 degrees of heat
  • a catalyst of Al2O3 or SiO2

org chem (7 decks)

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