6. (a) Which of these is the formula of a molecule of a hydrocarbon? Put a cross (X) in the box next to your answer - Edexcel - GCSE Chemistry - Question 6 - 2013 - Paper 1

The structure of propene (C₃H₆) can be represented as follows:

   H   H
    \ /
     C
   /   \
  H     C
         \
          C
         / \
        H   H

In this structure, the double bond between the first and second carbon atoms is clearly shown.

The balanced equation for the combustion of methane is:

$\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$ This equation indicates that one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.

Advantages:

• Bio-methane is renewable and sustainable, as it can be consistently produced from plant materials.
• The crops grown for bio-methane production can utilize carbon dioxide during photosynthesis, thus reducing greenhouse gases.
• It is often considered carbon neutral, because the carbon produced during combustion is offset by the carbon absorbed by the plants when they grow.

Disadvantages:

• Cultivating crops for bio-methane uses up arable land, which may otherwise be utilized for food production.
• Adverse weather conditions can affect crop yield and availability of bio-methane.
• The production process can have limitations, such as requiring significant transport and processing infrastructure.