Gases in the Atmosphere (Edexcel IGCSE Science (Double Award): Chemistry): Flashcards
Exam code: 4SD0
1/390Still learning
Know0
- FrontComposition of Air
State the approximate percentage of nitrogen in dry air.
Was this flashcard helpful?
Cards in this collection (39)
State the approximate percentage of nitrogen in dry air.
Nitrogen makes up approximately 80% (four-fifths) of dry air by volume. It is the most abundant gas in the atmosphere.
What are the four most abundant gases in dry air?
Nitrogen (approximately 80%)
Oxygen (approximately 20%)
Argon (a noble gas)
Carbon dioxide
Nitrogen and oxygen together make up almost the entire atmosphere.
True or False?
Oxygen makes up approximately 20% of dry air by volume.
True.
Oxygen makes up about one-fifth (approximately 20%) of dry air by volume. This proportion has remained roughly constant for around 200 million years.
When phosphorus burns in a sealed bell jar sitting in a trough of water, the water level inside the jar .......... .
When phosphorus burns in a sealed bell jar sitting in a trough of water, the water level inside the jar rises.
Why is phosphorus well-suited for determining the percentage of oxygen in air?
Phosphorus burns readily and continues to burn until all the available oxygen is used up, making the measurement of the volume decrease reliable. However, it is toxic so it must be handled with great care.
True or False?
Phosphorus is the only substance that can be used to determine the percentage of oxygen in air experimentally.
False.
Other metals and non-metals that react with oxygen can also be used, such as iron. The key requirement is that the substance reacts with and uses up all the available oxygen in the sealed space. Phosphorus is commonly used but is highly flammable and toxic, so must be handled with care.
Dry air contains approximately .......... % nitrogen and approximately .......... % oxygen by volume.
Dry air contains approximately 80 % nitrogen and approximately 20 % oxygen by volume.
What is the aim of the iron filings in a burette practical for determining the percentage of oxygen in air?
The iron filings (or iron wool) react with and remove the oxygen from the air sealed in the burette. As oxygen is used up, the water level in the burette rises to fill the space previously occupied by oxygen.
True or False?
In the iron filings burette experiment, results are recorded after 3 to 4 days.
True.
The experiment is left for 3 to 4 days to allow the iron to react with all the available oxygen. Reading the burette too early would give an inaccurate result as not all oxygen would have been used up.
In the burette oxygen experiment, the percentage of oxygen is calculated by dividing the volume of .......... used by the .......... volume of air, then multiplying by 100.
In the burette oxygen experiment, the percentage of oxygen is calculated by dividing the volume of oxygen used by the initial volume of air, then multiplying by 100.
How is the volume of oxygen calculated in the burette experiment?
The volume of oxygen is calculated by subtracting the final volume of air from the initial volume of air. The volume change equals the amount of oxygen that was removed by the reacting iron.
True or False?
The expected result for the percentage of oxygen in the iron burette experiment is approximately 20%.
True.
The expected result is approximately 20%, consistent with the known composition of air. In a worked example from the RN, the calculated value was 19.7%, which is close to this accepted figure.
In the burette experiment, the initial volume of air equals the burette volume plus the volume .......... the tap, minus the initial .......... level reading.
In the burette experiment, the initial volume of air equals the burette volume plus the volume below the tap, minus the initial water level reading.
Define combustion.
Combustion is the reaction of a substance with oxygen to produce oxides. All combustion reactions are exothermic, releasing heat energy.
What is observed when magnesium burns in oxygen?
Magnesium burns with an intense white flame and produces a white powder, magnesium oxide (MgO). The equation is: 2Mg (s) + O2 (g) → 2MgO (s).
True or False?
All combustion reactions are exothermic.
True.
Combustion always releases heat energy, making it an exothermic reaction. Combustion reactions can also be classified as oxidation reactions as oxygen is gained.
When sulfur burns in oxygen, it produces a .......... flame and a colourless, poisonous gas called .......... .
When sulfur burns in oxygen, it produces a blue flame and a colourless, poisonous gas called sulfur dioxide (SO2).
Write the word equation for the combustion of hydrogen.
Hydrogen + oxygen → water. The symbol equation is: 2H2 (g) + O2 (g) → 2H2O (g). The reaction is exothermic.
True or False?
Sulfur combustion produces a white solid product.
False.
The combustion of sulfur produces sulfur dioxide (SO2), which is a colourless, poisonous gas, not a solid. The equation is: S (s) + O2 (g) → SO2 (g).
The combustion of magnesium in oxygen produces .........., which appears as a white .......... after burning.
The combustion of magnesium in oxygen produces magnesium oxide, which appears as a white powder after burning.
Give the balanced symbol equation for the combustion of sulfur in oxygen.
S (s) + O2 (g) → SO2 (g). The product sulfur dioxide is a colourless gas with a poisonous, pungent smell.
Define thermal decomposition.
Thermal decomposition is a reaction in which a substance breaks down into simpler substances due to the action of heat.
What two products form when a metal carbonate is heated?
A metal oxide
Carbon dioxide gas
When copper(II) carbonate is heated it decomposes to form .......... and .......... .
When copper(II) carbonate is heated it decomposes to form copper(II) oxide and carbon dioxide.
True or False?
Copper(II) carbonate turns from green to black when heated.
True.
Copper(II) carbonate is a green powder. On heating it decomposes to form black copper(II) oxide.
How is carbon dioxide detected during thermal decomposition?
Carbon dioxide is detected by passing the gas through limewater, which turns milky in the presence of CO2.
The equation for the thermal decomposition of copper(II) carbonate is: CuCO3 (s) → .......... (s) + .......... (g).
The equation for the thermal decomposition of copper(II) carbonate is: CuCO3 (s) → CuO (s) + CO2 (g).
True or False?
All metal carbonates decompose when heated.
False.
Only carbonates of metals in the lower part of the reactivity series (those below calcium) tend to decompose on heating. Carbonates of very reactive metals such as potassium and sodium are too stable to decompose with a Bunsen burner flame.
What is the general word equation for the thermal decomposition of a metal carbonate?
The general word equation is: metal carbonate → metal oxide + carbon dioxide.
Define metal carbonate.
A metal carbonate is a compound containing a metal bonded to the carbonate ion (CO32-). Metal carbonates from the lower half of the reactivity series decompose on heating to give the metal oxide and carbon dioxide.
Define the greenhouse effect.
The greenhouse effect is the process by which greenhouse gases in the atmosphere absorb and trap long-wavelength infrared radiation from the Earth's surface, maintaining temperatures high enough to support life.
Name three greenhouse gases found in the Earth's atmosphere.
Carbon dioxide
Methane
Water vapour
True or False?
Carbon dioxide is the only greenhouse gas.
False.
Carbon dioxide is a greenhouse gas, but methane and water vapour are also greenhouse gases that contribute to warming the Earth's atmosphere.
The Sun emits .......... wavelength radiation. When this strikes the Earth's surface, some is re-emitted as .......... wavelength radiation.
The Sun emits short wavelength radiation. When this strikes the Earth's surface, some is re-emitted as long wavelength radiation.
Why do increasing levels of CO2 and CH4 cause the atmosphere to warm?
Increasing levels of CO2 and CH4 cause the atmosphere to warm because these greenhouse gases absorb and trap more infrared radiation re-emitted from the Earth's surface, preventing it from escaping into space.
True or False?
The greenhouse effect is entirely harmful and serves no useful purpose.
False.
The natural greenhouse effect maintains the Earth's mean temperature at around 15 °C. Without it, the Earth's average temperature would be about −18 °C, far too cold to support most life.
Two sources of carbon dioxide that increase its atmospheric concentration are .......... of fossil fuels and .......... of carbonate rocks.
Two sources of carbon dioxide that increase its atmospheric concentration are combustion of fossil fuels and thermal decomposition of carbonate rocks.
What is the difference between the greenhouse effect and the enhanced greenhouse effect?
The natural greenhouse effect is the process that keeps Earth at a habitable temperature. The enhanced greenhouse effect refers to the additional warming caused by rising concentrations of greenhouse gases from human activity, which may contribute to climate change.
Define greenhouse gas.
A greenhouse gas is a gas that absorbs and re-emits infrared radiation in the atmosphere, trapping heat and contributing to the greenhouse effect. Examples include carbon dioxide, methane and water vapour.
Sign up to unlock flashcards
or