Question 1: Define an alkane and state its general molecular formula.

Answer: An alkane is a saturated hydrocarbon with only single bonds between carbon atoms, and its general formula is CnH2n+2.

Question 2: Explain why alkanes are considered saturated hydrocarbons.

Answer: Alkanes are saturated hydrocarbons because they contain only single bonds between carbon atoms, with the maximum number of hydrogen atoms attached to each carbon.

Question 1: Calculate the number of hydrogen atoms in a molecule of decane (C10H22).

Answer: 22

Question 2: If 1 mole of octane (C8H18) undergoes complete combustion, calculate the volume of carbon dioxide produced at room temperature and pressure (assume ideal gas behaviour). (Use molar volume = 24 dm³/mol)

Answer: 432 dm³

Question 1: Describe a simple experimental method to test whether a hydrocarbon sample is an alkane or an alkene. Include safety precautions.

Answer: One method is to add bromine water to the sample. Alkanes do not decolourise bromine water because they are saturated, whereas alkenes decolourise bromine water due to the presence of double bonds. Safety precautions include wearing gloves and eye protection, and handling bromine water carefully as it is corrosive.

Question 1: A sample of an alkane burns with a blue flame producing 500 kJ of heat energy. If the molar enthalpy of combustion of this alkane is -5000 kJ/mol, how many moles of alkane are burned?

Answer: 0.1 mol

Question 1: Explain how alkanes are used in the industry for fuel and what environmental considerations are associated with their use.

Answer: Alkanes, such as methane and octane, are primary components of natural gas and petrol, used as fuels for heating, electricity, and transport. Their combustion releases energy but also produces carbon dioxide and pollutants such as sulphur oxides and nitrogen oxides, which contribute to climate change and air pollution. Sustainable alternatives and cleaner technologies are being developed to mitigate these environmental impacts.