This question is about gases - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2022 - Paper 1

The gas that bleaches damp litmus paper is chlorine (B). Chlorine is known for its bleaching properties and will cause the color of the litmus paper to change.

To find the mass of carbon dioxide released, we first calculate the difference between the initial mass of calcium carbonate and the remaining mass after heating:

Initial mass of CaCO3 = 5.000 g Remaining mass after heating = 2.800 g

Mass of CO2 released = Initial mass - Remaining mass = 5.000 g - 2.800 g = 2.200 g

Thus, the mass of carbon dioxide released is 2.20 g (to three significant figures).

Helium is inert because it has two electrons in its outer shell, which is the maximum capacity for its first shell. This full outer shell means that helium does not tend to gain, lose, or share electrons, making it stable and unreactive.

One property of helium that makes it suitable for filling balloons is that it is less dense than air. This low density allows helium-filled balloons to float.

The relative amounts of gases such as carbon dioxide, water vapour, and oxygen in the atmosphere have changed due to both natural processes and human activities. Natural origins, such as volcanic activity, released significant amounts of carbon dioxide and water vapour. Over time, as photosynthetic organisms evolved, oxygen levels increased in the atmosphere. Human activities, particularly the burning of fossil fuels, have led to rising levels of carbon dioxide. In contrast, the amount of water vapour has fluctuated based on climate conditions. Overall, while carbon dioxide has increased due to anthropogenic sources, water vapour has seen variable changes, and oxygen levels have steadily risen due to biological processes.