AP EAMCET · Chemistry · Classification of Elements and Periodicity in Properties

Which element among the following is most probable to have the following values?
\(\begin{aligned} \Delta_i H_1 & =419 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_i H_2 & =305 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_{\mathrm{eg}} H & =-48 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{aligned}\)

A \(\mathrm{Al}\)
B \(\mathrm{K}\)
C \(\mathrm{S}\)
D \(\mathrm{Cl}\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{K}\)

Step-by-step Solution

Detailed explanation

Atomic number of \(\mathrm{K}=19\) Electronic configuration \([\mathrm{Ar}] 4 s^1\) \(\mathrm{K} \longrightarrow \mathrm{K}^{+}+\mathrm{l} e^{-} ; \quad \Delta_i H_1=419 \mathrm{~kJ} / \mathrm{mol}\) Potassium has only one electron in outermost shell which looses easily to…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Which element among the following is most probable to have the following values?\(\begin{aligned} \Delta_i H_1 & =419 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_i H_2 & =305 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_{\mathrm{eg}} H & =-48 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{aligned}\)

Step-by-step Solution

Which element among the following is most probable to have the following values?
\(\begin{aligned} \Delta_i H_1 & =419 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_i H_2 & =305 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \Delta_{\mathrm{eg}} H & =-48 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{aligned}\)