3 (a) Carbon dioxide is one of the gases in the Earth's atmosphere - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2019 - Paper 1

Factor 1: Human Activity - The burning of fossil fuels for energy and transportation has significantly increased carbon dioxide levels in the atmosphere. Industrial processes and deforestation also contribute to this increase.

Factor 2: Natural Processes - Natural mechanisms such as volcanic eruptions can release large amounts of carbon dioxide, while photosynthesis by plants can decrease the concentration by absorbing carbon dioxide, leading to variations in atmospheric levels.

Carbon dioxide has a low boiling point due to the weak intermolecular forces, specifically van der Waals forces, between the molecules. These forces require less energy to overcome, resulting in a low boiling point of -78.5°C. The simple molecular structure of carbon dioxide means that it does not have strong intermolecular attractions compared to ionic or covalent compounds.

To calculate the number of molecules, first, we need to find the number of moles of carbon dioxide:

1. Find moles:

   Moles =
   \frac{mass}{molar mass} = \frac{0.11 g}{44 g/mol} = 0.0025 mol

2. Calculate the number of molecules using Avogadro's number:

   \text{Number of molecules} = moles \times \text{Avogadro's constant} = 0.0025 \text{ mol} \times 6.02 \times 10^{23} \text{ molecules/mol} \approx 1.51 \times 10^{21} \text{ molecules}.

Thus, the number of molecules in 0.11 g of carbon dioxide is approximately $1.5 \times 10^{21}$ to two significant figures.