Gases in the Atmosphere
6 marks · NormalThis question is about the properties of different oxides and the impact of carbon dioxide in the atmosphere.
When sulfur burns in oxygen, it produces an oxide. State whether the oxide formed is acidic or basic and explain your answer.
When magnesium burns in oxygen, it forms magnesium oxide. Predict whether magnesium oxide reacts with acids or with alkalis and give a reason for your answer.
State what is meant by the term 'greenhouse gas' and explain why carbon dioxide is classified as one.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Sulfur dioxide (the oxide formed) is an acidic oxide because it is a non-metal oxide and reacts with water to form an acidic solution. · must show Identification as acidic, Reason linked to non-metal oxide/reacts with water to form acid
(b) Magnesium oxide reacts with acids as it is a basic oxide (formed from a metal), and basic oxides react with acids to form salts. · must show Predicts reaction with acids, Gives reason (basic oxide/metal oxide/reacts with acids to make salt)
(c) A greenhouse gas is a gas that absorbs infrared radiation and causes warming of the atmosphere. Carbon dioxide is a greenhouse gas because its vibrating molecules can absorb infrared radiation emitted by the Earth’s surface. · must show Greenhouse gas definition (absorbs IR to warm atmosphere), Specific reason for CO2 (absorbs IR due to molecular vibrations)
Common mistakes: Confusing acidic and basic oxides; Stating that all oxides are basic; Saying only water is a greenhouse gas
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States that the oxide formed (sulfur dioxide) is acidic
B2 (a) · 1 mark · Explains why (non-metal oxide or reacts with water to form acid)
B3 (b) · 1 mark · Predicts magnesium oxide reacts with acids
B4 (b) · 1 mark · Gives correct reason (basic oxide/metal oxide/reacts with acids to make salt)
B5 (c) · 1 mark · Gives correct definition of greenhouse gas (absorbs IR and warms atmosphere)
B6 (c) · 1 mark · Explains why CO2 is a greenhouse gas (absorbs IR because of molecular vibration)
Worked solution
a) The oxide formed when sulfur burns in oxygen is sulfur dioxide, which is an acidic oxide. This is because sulfur is a non-metal. Non-metal oxides are usually acidic and react with water to form acidic solutions (sulfur dioxide dissolves to form sulfurous acid).
b) Magnesium oxide will react with acids because it is a basic oxide, as it is formed from a metal. Basic oxides react with acids to form a salt and water.
c) A greenhouse gas is a gas that absorbs infrared radiation from the Earth and helps warm the atmosphere. Carbon dioxide is a greenhouse gas because its molecules can vibrate in ways that cause changes in molecular polarity, allowing them to absorb infrared radiation.