4.5.2 Alkanes Flashcards

1
Q

What is the general formula of an alkane?

A

CnH2n+2

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2
Q

What is the formula of methane?

A

CH4

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3
Q

What is the formula of ethane?

A

C2H6

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4
Q

What is the formula of propane?

A

C3H8

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5
Q

What is the formula of butane?

A

C4H10

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6
Q

What is the formula of pentane?

A

C5H12

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7
Q

What type of bonds hold alkanes together?

A

Covalent bonds

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8
Q

What is the displayed formula?

A

A diagram showing the positions of every atom and every bond.

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9
Q

What is the structural formula?

A

Shows the structure of the molecule in one line, read left to right.
e.g. the structural formula of butane is CH3CH2CH2CH3

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10
Q

What is the molecular formula?

A

This only shows how many of each atom there are.

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11
Q

What is the empirical formula?

A

This only shows the simplest whole number ratio of atoms.

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12
Q

What is a homologous series?

A

A family of molecules that have similar chemical reactions, trends in physical properties and the same general formula.

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13
Q

What are isomers?

A

Isomers are molecules with the same molecular formula but different structural formulae.

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14
Q

Why are most alkanes used as fuels?

A

Most alkanes are used as fuels because they release a lot of energy when combusted.

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15
Q

When does complete combustion occur?

A

When there is excess oxygen.

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16
Q

What is the general equation for the complete combustion of an alkane?

A

Alkane + Oxygen –> Carbon dioxide + Water

17
Q

When does incomplete combustion occur?

A

When there is not enough oxygen.

18
Q

What happens in the incomplete combustion of an alkane?

A

Instead of CO2, a mixture of CO and C is produced. It also releases less energy.

19
Q

How is CO2 formed in terms of alkanes and the effects of it?

A

CO2 is formed directly from the combustion of alkanes. It is a greenhouse gas that traps heat in the atmosphere are causes climate change.

20
Q

How are nitrogen oxides formed in terms of alkanes and the effects of them?

A

Formed when the nitrogen from air combust. Usually nitrogen doesn’t combust but car engines are very hot. They dissolve in rainwater to form acid rain, which corrodes structures and is harmful to plant and aquatic life.

21
Q

How is SO2 formed in terms of alkanes and the effects of it?

A

This forms when sulphur impurities in the fuel combust. It dissolves in rainwater to form acid rain, which corrodes structures and is harmful to plant and aquatic life.

22
Q

What happens when alkanes react with halogens?

A

Alkanes react with halogens by swapping on hydrogen atom for one halogen atom.

23
Q

What kind of reaction is an alkane and halogen reaction?

A

A substitution reaction because H swaps with a halogen atom.

24
Q

What is needed for a substitution reaction?

A

UV light because alkanes are quite unreactive.

25
Q

Are alkanes saturated or not? why?

A

saturated because there is no C=C double bond.