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The nitrate ion, NO₃⁻, contains a dative covalent bond - CIE - A-Level Chemistry - Question 1 - 2013 - Paper 1
Question 1
The nitrate ion, NO₃⁻, contains a dative covalent bond. Complete the following 'dot-and-cross' diagram of the bonding in the nitrate ion. For each of the four atoms... show full transcript
Worked Solution & Example Answer:The nitrate ion, NO₃⁻, contains a dative covalent bond - CIE - A-Level Chemistry - Question 1 - 2013 - Paper 1
Step 1
The nitrate ion, NO₃⁻
Answer
The complete dot-and-cross diagram of the nitrate ion includes:
- Oxygen atoms each contributing 6 outer electrons with 2 pairs shown as 'o' and 'x'
- Nitrogen atom contributing 5 outer electrons, 2 of which form a dative bond with one oxygen atom, represented as 'o'
- The additional electron contributing to the negative charge shown as '□'
- Overall, there are 24 electrons in the diagram.
Step 2
Step 3
Describe and explain the trend that is observed in the thermal stabilities of the Group II nitrates.
Answer
As we move down the Group II nitrates, their thermal stability generally increases. This trend can be attributed to the following factors:
- The larger cations lower the charge density, which results in less polarization of the nitrate ion.
- Consequently, the N–O bonds are stronger in heavier Group II nitrates, making them less likely to decompose under heat.
Step 4
When concentrated nitric acid, HNO₃, is added to copper turnings, a brown gas is evolved.
Answer
The ionic equation for the reaction can be constructed as:
ightarrow Cu^{2+} + 2NO₂ + 2H₂O$$ This equation shows copper reacting with nitric acid to produce the brown gas nitrogen dioxide and water.