Question

A \(p\)-block element \(E\) and hydrogen form a binary cation \( (EH_x)^+ \), while \(EH_3\) on treatment with \(K_2HgI_4\) in alkaline medium gives a precipitate of basic mercury(II) amido-iodide. Given below are first ionisation enthalpy values (kJ mol\(^{-1}\)) for the first elements each from groups 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element \(E\).

• A. 1402
• B. 801
• C. 1312
• D. 1086

Hint:

Ammonia-like behavior and formation of ammonium-type ions are strong indicators of group 15 elements.

Answer 1

The Correct Option is A

Step 1: Identify the element type.
The formation of a binary cation \( (EH_x)^+ \) indicates that element \(E\) can form stable protonated species, which is characteristic of group 15 elements.
Step 2: Use the chemical test.
The formation of basic mercury(II) amido-iodide with \(K_2HgI_4\) in alkaline medium is a confirmatory test for ammonia and ammonia-like hydrides, again indicating a group 15 element.
Step 3: Match ionisation enthalpy.
The first ionisation enthalpy values of the first elements of groups are approximately: \[ \text{Group 13: } 801,\quad \text{Group 14: } 1086,\quad \text{Group 15: } 1402,\quad \text{Group 16: } 1312. \] Thus, element \(E\) belongs to group 15, and its first ionisation enthalpy is \[ 1402\ \text{kJ mol}^{-1}. \] Final Answer: \[ \boxed{1402} \]