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

One factor that causes variation in carbon dioxide levels is human activity, particularly the burning of fossil fuels, which releases additional CO₂ into the atmosphere.

Another factor is natural processes, such as volcanic activity or ocean absorption, which can both release and absorb carbon dioxide, affecting atmospheric levels.

Carbon dioxide has a low boiling point because it exists as a simple molecular compound with weak intermolecular forces (Van der Waals forces) between its molecules. These weak forces require little energy to break, hence allowing CO₂ to vaporize at low temperatures.

First, calculate the number of moles of CO₂:

Number of moles = mass / molar mass = 0.11 g / 44 g/mol = 0.0025 moles.

Using Avogadro's constant, we can then find the number of molecules:

Number of molecules = number of moles × Avogadro's constant = 0.0025 mol × 6.02 × 10²³ molecules/mol = 1.51 × 10²¹ molecules.

Therefore, the answer is approximately 1.5 × 10²¹ molecules, rounded to two significant figures.