This question is about silver iodide - AQA - A-Level Chemistry - Question 1 - 2017 - Paper 1
Question 1
This question is about silver iodide.
0 1 . 1 Define the term enthalpy of lattice formation.
Enthalpy of lattice formation is defined as the standard enthalpy chan... show full transcript
Worked Solution & Example Answer:This question is about silver iodide - AQA - A-Level Chemistry - Question 1 - 2017 - Paper 1
Step 1
0 1 . 1 Define the term enthalpy of lattice formation.
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Answer
Enthalpy of lattice formation is defined as the standard enthalpy change when one mole of an ionic solid is formed from its gaseous ions under standard conditions.
Step 2
0 1 . 2 Use the data in Table 1 to calculate the enthalpy of lattice formation of silver iodide.
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To calculate the enthalpy of lattice formation of silver iodide, we can use the provided enthalpy changes:
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The difference can be explained by considering that the perfect ionic model assumes that ions are point charges, neglecting their finite size and the effects of covalent character in ionic bonding. Real ionic compounds can exhibit some degree of covalent character, which affects the lattice energy.
Step 4
0 1 . 4 Identify a reagent that could be used to indicate the presence of iodide ions in an aqueous solution and describe the observation made.
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A reagent that could be used to indicate the presence of iodide ions is silver nitrate (AgNO₃). When silver nitrate is added to a solution containing iodide ions, a yellow precipitate of silver iodide (AgI) forms, indicating the presence of iodide ions.
