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Chemistry Unit 1 > test 2 - hydrocarbons (ch 8/11) > Flashcards

test 2 - hydrocarbons (ch 8/11) Flashcards

1
Q

what is an alkane?

A

an aliphatic - hydrocarbon that contain only single bonds - this means they are saturated (no space for new bond)

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2
Q

properties of carbon that allow it to the basis of so many things?

A

it has 4 valence electrons, allowing it to form 4 bonds with other non-metals - it can form single, double and triple bonds into varied lengths and shapes

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3
Q

examples of carbon based molecules?

A

caffeine, plastic and petrol

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4
Q

what is crude oil?

A

produced by the effects of heat and pressure on dead organisms in earth’s crust - it is a source of carbon compounds

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5
Q

how is crude oil made?

A

when the dead matter was pressured in the earth’s crust, the oils and fats from these organic materials turned into hydrocarbons

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6
Q

properties of crude oil?

A

low density - migrates up towards crust

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7
Q

properties of methane?

A

colourless, odourless gas, very flammable - main component of natural gas

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8
Q

properties of compounds of the same homologous series?

A
  1. similar structure
  2. a pattern to their physical properties
  3. similar chemical properties
  4. same general formula
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9
Q

how strong are the forces in alkanes?

A

they have weak force between the molecules as they are non-polar. bigger molecules are stronger with higher m/b points

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10
Q

alkane general formula?

A

C(n)H(2n +2)

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11
Q

what is a structural isomer in alkanes?

A

when alkanes have more than 4 carbon atoms (butane and above) they can have more than one possible structure

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12
Q

example of an alkane structural isomer?

A

with a side chain. for example, butane has a structural isomer called 2-methyl-propane (reference - pg.165)

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13
Q

how to write -alkyl groups (side chains) in condensed structure formula?

A

use brackets (reference pg. 168 figure 8.1.8)

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14
Q

do the chemical properties change for a structural isomer?

A

yes. the boiling and melting points differ

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15
Q

IUPAC system of naming alkane

name the following examples with this system:

  1. CH3-CH(CH3)-CH(CH3)-CH3
  2. CH3-CH2-CH(CH3)-CH2-CH3
A

answer to q1 is 2,3-dimethylbutane
answer to q2 is 3-methylpentane

  1. make sure it is a single bond
  2. longest chain of carbon? (methane, ethane, propane, butane)
  3. identify side chains (what is it? methyl, ethyl etc. - if more than one TYPE of side chain, name in alphabetical order)
  4. where is the side chain located? (lowest number)
  5. how many of the SAME side chain are there? (e.g. 4-dimethyl)
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16
Q

what is an alkene?

A

an aliphatic - hydrocarbon with at least one double bond - these are unsaturated - meaning they can break the bonds to form new bonds

17
Q

alkenes reactivity relative to alkane?

A

alkenes are more reactive, as they can form addition reactions (by breaking bonds)

18
Q

General formula for alkene?

A

C(n)H(2n)

19
Q

properties of alkenes?

A

non polar (do not dissolve in water)

20
Q

structural isomers in alkene?

A

when there are more than three carbon atoms a structural isomer will occur. these are numbered from the lowest number to the double bond

20
Q

what are geometric isomers in alkenes? (cis/trans)

A

joined in same order, but different arrangement. occurs because of the atoms around a double bond cannot rotate (they can in a single bond)

21
Q

how do cis isomers look?

A

the same group is located on the same side of the double bond (horizontal symmetry wise)

22
Q

how do trans isomers look?

A

the same group is located on the OPPOSITE side of the double bond (and only OPPOSITE side)

23
Q

IUPAC system of naming an alkene

name the following using this system:

  1. CH3-CH2-CH=CH2
  2. CH3-CH2-CH=CH-CH3
A

answer of q1 is but-1-ene
answer of q2 is pent-2-ene

  1. identify longest carbon chain (must include double bond)
  2. number carbon atoms in a way that will result in the smallest number for the double bond
  3. where is the double bond located? (but-1-ene)
  4. side chain (what are they)
  5. where are the side chains located (double bond precedes anything else - number from where double bond is lowest number)
  6. how many side chains (di-, tri-)
24
Q

what is benzene?

A

an aromatic which is a stable, flat, hexagonal ring. the bond length is intermediate between single and double, so its neither single, not double - like 1.5 bond

25
Q

how are halogen side chains named?

A

F = fluoro

Cl = Chloro

Br = Bromo

I = Iodo

26
Q

how do the bonds in benzene work?

A

the electrons that make up the double bonds are not in fixed position - they are delocalised and can move around the ring

27
Q

what are the two types of reactions hydrocarbons undergo?

A
  1. substitution
  2. addition
28
Q

why are hydrocarbons useful for fuels?

A

they all undergo combustion reactions, reacting with oxygen in exothermic reactions

29
Q

what are substitution reactions? how do they work?

A

in alkAnes. in the presence of UV light, a C-H bond is broken and replaced with a C-halogen bond. This results in an inorganic product produced

30
Q

why do substitution reactions occur in alkanes?

A

they are saturated, cannot add extra molecules without breaking some first

31
Q

can benzene undergo substitution reactions?

A

yes but they need a catalyst and UV light

32
Q

Name the 4 types of addition reactions?

A
  1. with hydrogen
  2. with halogens
  3. with water
  4. with hydrogen halides
33
Q

what are addition reactions? how do they work?

A

two reactant molecules combine to form one product molecule. this occurs in unsaturated molecules (alkEnes) as they can break the double bonds allowing space for the new molecule

34
Q

When an addition reaction occurs with hydrogen halides, what can occur?

A

two isomers can occur as the molecule being added contains more than one type of element

35
Q

what is combustion?

A

the reaction between a fuel and oxygen - combustion reactions release huge amounts of energy, hence used as fuels

36
Q

complete combustion?

A

fuel + oxygen → carbon dioxide + water. plentiful supply of oxygen

37
Q

incomplete combustion?

A

fuel + oxygen → carbon monoxide + soot + water

Chemistry Unit 1 (3 decks)

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