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5 (a) Sulfur dioxide combines with oxygen to form sulfur trioxide in an exothermic reaction - Edexcel - GCSE Chemistry - Question 5 - 2017 - Paper 1
Question 5
5 (a) Sulfur dioxide combines with oxygen to form sulfur trioxide in an exothermic reaction. 2SO2(g) + O2(g) ⇌ 2SO3(g) The reaction can reach equilibrium. At 2 at... show full transcript
Worked Solution & Example Answer:5 (a) Sulfur dioxide combines with oxygen to form sulfur trioxide in an exothermic reaction - Edexcel - GCSE Chemistry - Question 5 - 2017 - Paper 1
Step 1
When a temperature higher than 450 °C is used, the equilibrium yield of sulfur trioxide decreases.
Answer
In an exothermic reaction, increasing the temperature shifts the equilibrium position to favor the endothermic direction to absorb the added heat. Thus, for the reaction
[ 2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g) ]
increasing the temperature will shift the equilibrium towards the reactants, resulting in a decrease in the equilibrium yield of sulfur trioxide (SO3). This is in accordance with Le Chatelier's principle, which states that a system at equilibrium will adjust to counteract any changes in conditions, such as temperature.
Step 2
Describe how the apparatus below can be used to obtain these results, showing how the results can be used to find the volume occupied by one mole of hydrogen gas, H2, at room temperature and pressure.
Answer
To determine the volume of hydrogen gas produced, the magnesium ribbon is first placed in excess dilute sulfuric acid in a flask. The flask is equipped with a delivery tube leading to an inverted graduated gas jar or a measuring cylinder filled with water (to capture the gas).
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Add excess dilute sulfuric acid to the flask containing magnesium ribbon.
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Allow the reaction to proceed, which produces hydrogen gas (H2) as shown in the equation:
[ Mg(s) + H_2SO_4(aq) \rightarrow MgSO_4(aq) + H_2(g) ]
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Collect the hydrogen gas in the inverted container, noting the volume of gas produced.
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The gas volume at room temperature and pressure can then be measured from the gas jar or measuring cylinder.
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Using the molar volume of a gas at room temperature and pressure (approximately 24.0 dm³/mol), you can calculate the number of moles of hydrogen produced from the volume collected, and subsequently determine the volume occupied by one mole of hydrogen gas under the same conditions.