This question is about some elements in Group 7 and their compounds - AQA - A-Level Chemistry - Question 6 - 2022 - Paper 1
Question 6
This question is about some elements in Group 7 and their compounds.
1. Chlorine is added to some drinking water supplies to decrease the risk of people suffering f... show full transcript
Worked Solution & Example Answer:This question is about some elements in Group 7 and their compounds - AQA - A-Level Chemistry - Question 6 - 2022 - Paper 1
Step 1
State why the amount of chlorine added must be controlled.
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Answer
The amount of chlorine added must be controlled because chlorine is toxic and can cause harm or even death if present in excessive amounts.
Step 2
Give an equation for the reaction of chlorine with water to form a solution containing two acids.
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Answer
The equation for the reaction is:
Cl2+H2O→HCl+HClO
Explanation: This is a redox reaction because chlorine is reduced and water is oxidized. Chlorine gains electrons to form chloride ions (Cl⁻), and water loses electrons, forming hydrochloric acid (HCl) and hypochorous acid (HClO).
Step 3
State the observation the student would make.
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The student would observe a brown solution or black solid (iodine).
Step 4
Give an ionic equation for the reaction.
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The ionic equation for the reaction between chlorine gas and sodium iodide is:
Cl2+2NaI→2NaCl+I2
Step 5
Give an equation for the formation of these sulfur-containing products.
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One possible equation is:
H2SO4+2NaI→2HI+Na2SO4
Another valid equation is:
H2SO4+2NaI→SO2+2HI+Na2SO4
Step 6
State the role of sulfuric acid in the formation of these products.
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Sulfuric acid acts as an oxidizing agent in this reaction, facilitating the oxidation of iodide ions to iodine.
Step 7
Deducce the identity of the sodium halide.
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The identity of the sodium halide is sodium iodide (NaI).
Step 8
Suggest the identity of the gas.
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The identity of the gas is hydrogen iodide (HI).
Step 9
Give an ionic equation for the formation of this gas from the impurity.
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The ionic equation for the formation of hydrogen iodide gas when sodium iodide reacts with sulfuric acid is:
2NaI+H2SO4→2HI+Na2SO4
Step 10
Use your understanding of the electron pair repulsion theory to draw the shape of this ion.
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The shape of the ClF2− ion is linear due to two bonded pairs and three lone pairs of electrons, which repel each other and arrange themselves as far apart as possible.
Step 11
Explain why the ion has the shape you have drawn.
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The ion has a linear shape because the three lone pairs of electrons repel the bonded pairs of electrons, leading to a geometry that minimizes repulsion, resulting in a linear arrangement.
Step 12
Suggest a value for the bond angle in the ion.
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The bond angle in this ion is approximately 180 degrees.
Step 13
Give an equation for this reaction.
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