GCSE Chemistry - Hydrocarbons - Alkanes & Homol | AnkiDecks

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GCSE Chemistry - Hydrocarbons - Alkanes & Homol ...

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1 / 23 P&R

What does organic chemistry study?

Compounds that contain carbon

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2 / 23 P&R

Why is carbon useful for making large compounds?

Because each carbon atom can form four strong bonds

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3 / 23 P&R

Which atoms are the most common partners bonded to carbon in large organic molecules?

Other carbon atoms
Hydrogen atoms

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4 / 23 P&R

What is a hydrocarbon?

Any compound formed from carbon and hydrogen only

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5 / 23 P&R

What specific class of hydrocarbons is the video focusing on?

Alkanes

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6 / 23 P&R

What defines a 'hydrocarbon'?

A compound that contains only carbon and hydrogen atoms.

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Why is butane a hydrocarbon but butanol is not?

Butane contains only C and H (C4H10); butanol also has an oxygen atom, so it is not a hydrocarbon.

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8 / 23 P&R

What are 'alkanes'?

The simplest group of hydrocarbons that are saturated (only single bonds).

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9 / 23 P&R

What is the general formula for alkanes?

The general formula is \(\mathrm{C_nH_{2n+2}}\).

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10 / 23 P&R

What is the first alkane and its formula?

Methane
CH4

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11 / 23 P&R

Name the first four alkanes with their formulas.

Methane — CH4
Ethane — C2H6
Propane — C3H8
Butane — C4H10

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How does each consecutive alkane in the series differ?

Each successive alkane adds one CH2 unit to extend the carbon chain.

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13 / 23 P&R

What is a homologous series in organic chemistry?

A homologous series is a group of organic compounds that have similar properties and react in a similar way.

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14 / 23 P&R

Which are the first four alkanes shown?

Methane
Ethane
Propane
Butane

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15 / 23 P&R

What is the general formula for alkanes?

The general formula for alkanes is \(\mathrm{C_nH_{2n+2}}\).

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What does the alkane general formula \(\mathrm{C_nH_{2n+2}}\) mean in words?

If the compound contains 'n' carbon atoms, then it contains 2 times 'n' plus 2 hydrogen atoms.

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Using the general formula, what is the hydrogen count when n = 3?

For n = 3 the calculation is \((2\times 3)+2 = 8\), so there are 8 hydrogen atoms.

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18 / 23 P&R

What is the molecular formula of propane?

Propane has the molecular formula C3H8.

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What formula gives the number of hydrogen atoms in an alkane with n carbon atoms?

The number of hydrogens is given by \(2n+2\).

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Using the general alkane hydrogen formula, how many hydrogen atoms does octane (n=8) have?

Calculate \((2\times 8)+2 = 18\), so octane has 18 hydrogens.

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What is the molecular formula of octane?

Octane's molecular formula is \(C_8H_{18}\).

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What does it mean for alkanes to be 'saturated compounds'?

Every carbon atom has four single covalent bonds and there are no double bonds.

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What happens to a propane molecule if one C–C single bond is changed to a double bond?

Each carbon involved loses a hydrogen and the molecule is no longer an alkane but an alkene.

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Flashcards in this deck (23)

Pesquisando...

What does organic chemistry study?
- Compounds that contain carbon
organic definition
Why is carbon useful for making large compounds?
- Because each carbon atom can form four strong bonds
carbon bonding
Which atoms are the most common partners bonded to carbon in large organic molecules?
- Other carbon atoms
- Hydrogen atoms
bonding atoms
What is a hydrocarbon?
- Any compound formed from carbon and hydrogen only
hydrocarbon definition
What specific class of hydrocarbons is the video focusing on?
- Alkanes
alkanes topic
What defines a 'hydrocarbon'?

A compound that contains only carbon and hydrogen atoms.

hydrocarbons definition
Why is butane a hydrocarbon but butanol is not?

Butane contains only C and H (C4H10); butanol also has an oxygen atom, so it is not a hydrocarbon.

examples hydrocarbons
What are 'alkanes'?

The simplest group of hydrocarbons that are saturated (only single bonds).

alkanes definition
What is the general formula for alkanes?

The general formula is \(\mathrm{C_nH_{2n+2}}\).

alkanes formula
What is the first alkane and its formula?
- Methane
- CH4
alkanes members
Name the first four alkanes with their formulas.
- Methane — CH4
- Ethane — C2H6
- Propane — C3H8
- Butane — C4H10
alkanes members
How does each consecutive alkane in the series differ?

Each successive alkane adds one CH2 unit to extend the carbon chain.

homologous growth
What is a homologous series in organic chemistry?

A homologous series is a group of organic compounds that have similar properties and react in a similar way.

homologous organic
Which are the first four alkanes shown?
- Methane
- Ethane
- Propane
- Butane
alkanes names
What is the general formula for alkanes?

The general formula for alkanes is \(\mathrm{C_nH_{2n+2}}\).

alkanes formula
What does the alkane general formula \(\mathrm{C_nH_{2n+2}}\) mean in words?

If the compound contains 'n' carbon atoms, then it contains 2 times 'n' plus 2 hydrogen atoms.

alkanes interpretation
Using the general formula, what is the hydrogen count when n = 3?

For n = 3 the calculation is \((2\times 3)+2 = 8\), so there are 8 hydrogen atoms.

example calculation
What is the molecular formula of propane?

Propane has the molecular formula C3H8.

propane formula
What formula gives the number of hydrogen atoms in an alkane with n carbon atoms?

The number of hydrogens is given by \(2n+2\).

alkanes formula
Using the general alkane hydrogen formula, how many hydrogen atoms does octane (n=8) have?

Calculate \((2\times 8)+2 = 18\), so octane has 18 hydrogens.

octane calculation
What is the molecular formula of octane?

Octane's molecular formula is \(C_8H_{18}\).

octane molecular-formula
What does it mean for alkanes to be 'saturated compounds'?

Every carbon atom has four single covalent bonds and there are no double bonds.

saturated alkanes
What happens to a propane molecule if one C–C single bond is changed to a double bond?

Each carbon involved loses a hydrogen and the molecule is no longer an alkane but an alkene.

propane alkene

Notas de estudo

Alkanes — concise study notes

Big picture

Organic chemistry studies compounds containing carbon. Carbon commonly bonds to other carbons and to hydrogen because each carbon forms four strong bonds.

Hydrocarbons

Hydrocarbon: a compound containing only carbon and hydrogen. Example: butane (C4H10) is a hydrocarbon; butanol (contains O) is not.

Alkanes (definition and examples)

Alkanes are the simplest hydrocarbons and are saturated (only single covalent C–C bonds).
You must know the first four alkanes and their molecular formulas:
Methane — \(\mathrm{CH_4}\)
Ethane — \(\mathrm{C_2H_6}\)
Propane — \(\mathrm{C_3H_8}\)
Butane — \(\mathrm{C_4H_{10}}\)
Each successive alkane differs by a –CH_2– unit (chain growth by one carbon).

Homologous series and general formula

Alkanes form a homologous series: members have similar chemical properties and follow a pattern.
General molecular formula for alkanes: \(\mathrm{C_nH_{2n+2}}\).
Example (propane): if \(n=3\) then hydrogen atoms \(=2\times3+2\), so \(\mathrm{C_3H_8}\).
Example (octane): if \(n=8\) then hydrogen atoms \(=2\times8+2\), so \(\mathrm{C_8H_{18}}\).

Saturation vs unsaturation

Saturated means every carbon has four single covalent bonds; there are no double bonds in alkanes.
Introducing a C=C double bond produces an alkene and reduces the number of hydrogens (e.g., propane \(\mathrm{C_3H_8}\) → propene \(\mathrm{C_3H_6}\)).

Key points to remember

Carbon is tetravalent: forms up to four bonds, enabling long chains and rings.
Hydrocarbons = only C and H; adding other atoms (O, N, etc.) means "not a hydrocarbon."
Alkanes: saturated, general formula \(\mathrm{C_nH_{2n+2}}\), first four as above.
Homologous series = predictable formulas and similar reactivity; add CH2 to go to the next member.
Combustion and detailed properties of alkanes are typically covered separately.

Quick revision checklist

Can you list the first four alkanes and formulas? Yes: CH4, C2H6, C3H8, C4H10.
Can you apply \(\mathrm{C_nH_{2n+2}}\) to compute formulas for any n? Try \(n=5\) or \(n=10\).
Do you know the difference between saturated (alkane) and unsaturated (alkene) hydrocarbons?