State four differences between organic and inorganic compounds. Give three examples of carbon compounds which are not organic. Name the three main sources of organic compounds. List the properties of

Question 1:

i) State four differences between organic and inorganic compounds.

• Organic compounds contain carbon-hydrogen bonds; inorganic compounds generally do not.
• Organic compounds are typically covalent; inorganic compounds are often ionic.
• Organic compounds usually have lower melting and boiling points; inorganic compounds often have higher melting and boiling points.
• Organic compounds are generally flammable; inorganic compounds are typically non-flammable.

ii) Give three examples of carbon compounds which are not organic compounds.

• Carbon dioxide ($CO_2$)
• Calcium carbonate ($CaCO_3$)
• Carbon monoxide ($CO$)

iii) Name the three main sources of organic compounds.

• Fossil fuels (petroleum, natural gas, coal)
• Living organisms (plants and animals)
• Synthesis (laboratory and industrial processes)

iv) List the properties of carbon that enables it to form many stable compounds.

• Catenation: Carbon atoms can form strong bonds with other carbon atoms, creating long chains, branched chains, and rings.
• Tetravalency: Carbon has a valency of four, allowing it to form four stable covalent bonds.
• Ability to form multiple bonds: Carbon can form single, double, and triple bonds with other carbon atoms and other elements.
• Small size: The small size of carbon atoms allows for strong and stable covalent bonds.

Question 2:

i) What is meant by homologous series?
A homologous series is a series of organic compounds with the same general formula, similar chemical properties, and successive members differing by a $CH_2$ group.

ii) State four properties of a homologous series.

• All members have the same general formula.
• Successive members differ by a $CH_2$ group.
• They show a gradual change in physical properties as molecular mass increases.
• They have similar chemical properties due to the same functional group.

iii) Give four examples of family of compounds of the same homologous series.

• Alkanes (e.g., methane, ethane)
• Alkenes (e.g., ethene, propene)
• Alcohols (e.g., methanol, ethanol)
• Carboxylic acids (e.g., methanoic acid, ethanoic acid)

Question 3:

i) Define a hydrocarbon? Give one example each of three groups of hydrocarbons.
A hydrocarbon is an organic compound composed solely of hydrogen and carbon atoms.

• Alkanes: Methane ($CH_4$)
• Alkenes: Ethene ($C_2H_4$)
• Alkynes: Ethyne ($C_2H_2$)

ii) What is a functional group? State and give the structure of the functional groups of the following classes of organic compounds: alkanols, alkynes, alkanoic acids and alkanoates.
A functional group is an atom or group of atoms within a molecule that determines its characteristic chemical reactions.

• Alkanols: Hydroxyl group, $-OH$.

$$\text{R-OH}$$

• Alkynes: Carbon-carbon triple bond, $-C \equiv C-$.

$$\text{R-C} \equiv \text{C-R'}$$

• Alkanoic acids: Carboxyl group, $-COOH$.

$$\text{R-COOH}$$

• Alkanoates: Ester group, $-COO-$.

$$\text{R-COO-R'}$$

iii) State the general formulae of the following family of organic compounds and give two examples of each: alkanes, alkenes, alkynes, alkanols.

• Alkanes: $C_nH_{2n+2}$
  • Examples: Methane ($CH_4$), Ethane ($C_2H_6$)
• Alkenes: $C_nH_{2n}$
  • Examples: Ethene ($C_2H_4$), Propene ($C_3H_6$)
• Alkynes: $C_nH_{2n-2}$
  • Examples: Ethyne ($C_2H_2$), Propyne ($C_3H_4$)
• Alkanols: $C_nH_{2n+1}OH$
  • Examples: Methanol ($CH_3OH$), Ethanol ($C_2H_5OH$)

iv) Name three sources of alkanes.

• Petroleum (crude oil)
• Natural gas
• Coal

v) Distinguish between saturated and an unsaturated hydrocarbon. Give one example of each type of hydrocarbon.

• Saturated hydrocarbons contain only carbon-carbon single bonds. They have the maximum number of hydrogen atoms possible.
  • Example: Ethane ($C_2H_6$)
• Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond. They have fewer hydrogen atoms than the corresponding saturated hydrocarbon.
  • Example: Ethene ($C_2H_4$)

Question 4:

i) Write the molecular formulae of the following hydrocarbons, a named

a) four carbon alkane
The general formula for an alkane is $C_nH_{2n+2}$. For $n=4$:

$$C_4H_{2(4)+2} = C_4H_{10}$$

Name: Butane
Molecular formula: $\boxed{\text{C}_4\text{H}_{10}}$

b) four carbon alkene
The general formula for an alkene is $C_nH_{2n}$. For $n=4$:

$$C_4H_{2(4)} = C_4H_8$$

Name: Butene
Molecular formula: $\boxed{\text{C}_4\text{H}_8}$

c) two carbon alkyne
The general formula for an alkyne is $C_nH_{2n-2}$. For $n=2$:

$$C_2H_{2(2)-2} = C_2H_2$$

Name: Ethyne
Molecular formula: $\boxed{\text{C}_2\text{H}_2}$

Question 5:

i) Give the functional groups of the following and give one example of each

a) alkanoic acid
Functional group: Carboxyl group ($-COOH$)
Example: Ethanoic acid ($CH_3COOH$)

b) alkanoate ester
Functional group: Ester group ($-COO-$)
Example: Methyl ethanoate ($CH_3COOCH_3$)