Photo AI
This question is about gases - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Question 9
This question is about gases. (a) When sodium is added to water, hydrogen gas is produced. Which observation shows that a gas has been produced? (b) Some damp lit... show full transcript
Worked Solution & Example Answer:This question is about gases - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Step 1
When sodium is added to water, hydrogen gas is produced. Which observation shows that a gas has been produced?
Answer
The correct observation that indicates gas production when sodium is added to water is option B: effervescence is seen. This effervescence is a visible sign of hydrogen gas bubbles being released.
Step 2
Step 3
When 5.000g of calcium carbonate is heated, the mass of solid remaining is 2.800g. Calculate the mass of carbon dioxide that has been released.
Answer
The mass of carbon dioxide released can be calculated using the initial mass of calcium carbonate and the remaining mass after heating.
Initial mass = 5.000g Remaining mass = 2.800g
Mass of CO2 released = Initial mass - Remaining mass Mass of CO2 released = 5.000g - 2.800g = 2.200g
Thus, the mass of carbon dioxide that has been released is 2.20g, rounded to three significant figures.
Step 4
A diagram of an atom of helium is shown in Figure 15. Explain, using Figure 15, why helium is inert.
Answer
Helium is considered inert because it has a complete outer shell of electrons. From the diagram in Figure 15, we can see that helium has two electrons in its outer shell, fulfilling the octet rule. As a result, helium is stable and does not readily engage in chemical reactions with other elements.
Step 5
Helium is used to fill balloons. State one property of helium, apart from being inert, that makes it suitable for filling balloons.
Answer
One suitable property of helium is that it is less dense than air. This lower density allows helium-filled balloons to float, making them ideal for decoration and entertainment.
Step 6
Explain how the relative amount of each of the gases in Figure 16 has increased or decreased over time.
Answer
Over time, the composition of Earth's atmosphere has changed due to natural processes and human activities.
- Water vapor has decreased significantly as Earth cooled, leading to the formation of oceans.
- Carbon dioxide levels have decreased due to its absorption by oceanic processes and the fixing of carbon through photosynthesis by plants.
- On the other hand, the amount of oxygen has increased markedly due to the photosynthetic activity of plants and algae, which release oxygen as a byproduct of photosynthesis. This increase in oxygen has been crucial for the evolution of aerobic life forms.