SPI Chemistry · Free notes

Carbon and Its Compounds: SPI Chemistry

Carbon and Its Compounds has 12 questions in the SPI bank, and three of them are from the 2022 paper: two ask you to name a ring of six carbons from a drawing, and one asks the boiling point of ethanol. Five are EASY, seven are MODERATE and none is HARD. Nearly every question turns on a name or a structure: what the ending of a name says about its bonds, which allotrope has layers, which reaction an equation shows. Learn the names and the bonds behind them, and these are quick marks.

The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.

SPI home All formulas on one page

Subtopic notes

Formula & revision sheet

2 formulas · 6 reference tables · 14 gotchas across all subtopics — the exam-eve cheat-sheet

Carbon Bonding and Hydrocarbons

Formulas (2)

Covalent bonds and how to count them · Covalent bonds in an alkane $\text{bonds in } \mathrm{C}_n\mathrm{H}_{2n+2} = (n - 1) + (2n + 2) = 3n + 1$
Homologous series and isomers · Mass step in a homologous series $M_{\text{next}} = M + 14 \text{ u} \qquad \mathrm{CH_2} = 12 + 2 \times 1 = 14 \text{ u}$

Reference tables (2)

Allotropes of carbon3 rows

Allotrope	Each carbon bonds to	Structure	Key property
Diamond	4 carbons	Rigid three-dimensional network	Hardest natural substance, does not conduct
Graphite	3 carbons	Hexagonal layers, one above another	Soft, slippery, conducts electricity Graphite is the only one of the three that conducts.
Fullerene	3 carbons	Closed cage, $\mathrm{C_{60}}$ is a football shape	Separate molecules, not one giant network

Same atoms, different arrangements: that is what allotropes means.

Alkanes, alkenes, alkynes and rings6 rows

Family	General formula	Bonds	Example
Alkane	$\mathrm{C}_n\mathrm{H}_{2n+2}$	Single only	Methane $\mathrm{CH_4}$ , propane $\mathrm{C_3H_8}$
Alkene	$\mathrm{C}_n\mathrm{H}_{2n}$	One double bond	Ethene $\mathrm{C_2H_4}$ , propene $\mathrm{C_3H_6}$
Alkyne	$\mathrm{C}_n\mathrm{H}_{2n-2}$	One triple bond	Ethyne $\mathrm{C_2H_2}$ , propyne $\mathrm{C_3H_4}$
Cycloalkane	$\mathrm{C}_n\mathrm{H}_{2n}$	Ring of single bonds	Cyclohexane $\mathrm{C_6H_{12}}$ A ring has the same general formula as an alkene, but no double bond.
Cycloalkene	$\mathrm{C}_n\mathrm{H}_{2n-2}$	Ring with one double bond	Cyclohexene $\mathrm{C_6H_{10}}$
Benzene	$\mathrm{C_6H_6}$	Ring, alternate single and double bonds	Benzene

In a drawn ring, each corner is a carbon: count the double bonds to name it.

Watch out for (7)

Counting only the carbon-hydrogen bonds
→ Covalent bonds and how to count them
Thinking carbon forms ions
→ Covalent bonds and how to count them
Calling diamond a conductor because it is carbon
→ Allotropes of carbon
Taking a ring for an alkene
→ Alkanes, alkenes, alkynes and rings
Counting the single bonds next to a triple bond
→ Alkanes, alkenes, alkynes and rings
Saying isomers have the same structure
→ Homologous series and isomers
Expecting the physical properties to stay the same
→ Homologous series and isomers

Reactions, Ethanol and Ethanoic Acid

Reference tables (4)

Combustion, oxidation, addition and substitution4 rows

Reaction	Which compounds	Example
Combustion	All hydrocarbons	$\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O}$
Oxidation	Alcohols, then aldehydes	Ethanol to ethanoic acid, which turns blue litmus red
Addition	Unsaturated only	$\mathrm{C_2H_4 + H_2 \rightarrow C_2H_6}$ (nickel catalyst) Alkenes and alkynes add; alkanes cannot.
Substitution	Saturated hydrocarbons	$\mathrm{CH_4 + Cl_2 \rightarrow CH_3Cl + HCl}$ (sunlight)

Unsaturated means a double or triple bond: that is what lets a compound add.

Ethanol5 rows

Fact	Ethanol
Formula	$\mathrm{C_2H_5OH}$
Boiling point	About 78 °C (351 K)
With sodium	$\mathrm{2Na + 2C_2H_5OH \rightarrow 2C_2H_5ONa + H_2}$ The gas is hydrogen: it burns with a pop.
With hot concentrated sulphuric acid	Loses water to give ethene, $\mathrm{C_2H_4}$
Uses	Solvent, medicines such as cough syrups, fuel

Ethanol is the second member of the alcohols, after methanol.

Ethanoic acid4 rows

Reacts with	Products
Sodium hydroxide	$\mathrm{CH_3COOH + NaOH \rightarrow CH_3COONa + H_2O}$
Sodium carbonate	$\mathrm{2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2}$ The fizzing is carbon dioxide: it turns lime water milky.
Blue litmus	Turns red
Ethanol (concentrated sulphuric acid)	Ethyl ethanoate, a sweet-smelling ester

Sodium ethanoate,

\mathrm{CH_3COONa}

, is the salt in every row that makes one.

Esters, saponification and soap3 rows

Reaction	Reactants	Products
Esterification	$\mathrm{CH_3COOH + C_2H_5OH}$ , with concentrated $\mathrm{H_2SO_4}$	$\mathrm{CH_3COOC_2H_5 + H_2O}$
Saponification	Ester + sodium hydroxide	Sodium salt of the acid + alcohol Saponification starts from an ester and an alkali.
Soap making	Oil or fat + sodium hydroxide	Soap + glycerol

Ethyl ethanoate,

\mathrm{CH_3COOC_2H_5}

, is the ester of ethanoic acid and ethanol.

Watch out for (7)

Expecting an alkane to add
→ Combustion, oxidation, addition and substitution
Calling ethanol a hydrocarbon
→ Combustion, oxidation, addition and substitution
Mixing up the boiling points
→ Ethanol
Expecting carbon dioxide from sodium and ethanol
→ Ethanol
Taking ethanoic acid for a strong acid
→ Ethanoic acid
Saying the gas is hydrogen
→ Ethanoic acid
Swapping esterification and saponification
→ Esters, saponification and soap

Question weightage by concept

8 concepts · 12 questions — where the marks actually sit, so you know what to drill first

Carbon Bonding and Hydrocarbons7 questions · 58%

Concept	Qs	Share
Alkanes, alkenes, alkynes and rings	3	25%
Homologous series and isomers	2	17%
Covalent bonds and how to count them	1	8%
Allotropes of carbon	1	8%

Reactions, Ethanol and Ethanoic Acid5 questions · 42%

Concept	Qs	Share
Combustion, oxidation, addition and substitution	2	17%
Ethanol	1	8%
Ethanoic acid	1	8%
Esters, saponification and soap	1	8%

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