Question

An element 'E' has the ionisation enthalpy value of 374 kJ mol\(^{-1}\). 'E' reacts with elements A, B, C, and D with electron gain enthalpy values of −328, −349, −325, and −295 kJ mol\(^{-1}\), respectively. The correct order of the products EA, EB, EC, and ED in terms of ionic character is:

• A. EA > EB > EC > ED
• B. ED > EC > EA > EB
• C. ED > EC > EB > EA
• D. EB > EA > EC > ED

Hint:

A larger difference between the ionization enthalpy and electron gain enthalpy generally leads to more ionic bonds.

Answer 1

The Correct Option is C

To determine the correct order of the products EA, EB, EC, and ED in terms of ionic character, we need to consider the concept of electronegativity. The ionic character of a compound is influenced by the difference in electronegativity between the two elements involved. Greater differences in electronegativity lead to higher ionic character.

Given:

• Ionisation enthalpy of element E: 374 kJ mol⁻¹
• Electron gain enthalpy values:
  • A: −328 kJ mol⁻¹
  • B: −349 kJ mol⁻¹
  • C: −325 kJ mol⁻¹
  • D: −295 kJ mol⁻¹

To ascertain ionic character, we focus on the element with the least negative electron gain enthalpy, indicating lower electron affinity and thus a higher difference in electronegativity when combined with E. Elements with less negative electron gain enthalpy values will tend to form compounds with greater ionic character when bonded with elements of lower ionization enthalpy.

The electron gain enthalpy values show the following order (least to most negative):

• D: −295 kJ mol⁻¹
• C: −325 kJ mol⁻¹
• A: −328 kJ mol⁻¹
• B: −349 kJ mol⁻¹

The less negative the electron gain enthalpy, the greater the ionic character as E forms an ionic bond with these elements. Therefore, the correct order of ionic character is:

ED > EC > EB > EA

Answer 2

Step 1: Understand the given data.
The element 'E' has an ionisation enthalpy of 374 kJ mol⁻¹. This value is quite low, suggesting that element 'E' readily loses an electron and thus forms a cation easily. The elements A, B, C, and D have electron gain enthalpy values of −328, −349, −325, and −295 kJ mol⁻¹ respectively.

Step 2: Recall the concept of ionic character.
The ionic character of a compound depends on the difference in electronegativity between the two combining elements. A higher difference in the tendency to lose and gain electrons results in greater ionic character.
In this case:
- The smaller (more negative) the electron gain enthalpy value, the greater the tendency of the element to gain an electron (i.e., higher electronegativity).
- The smaller the ionisation enthalpy of 'E', the easier it loses an electron.

Thus, the greater the difference between the ionisation enthalpy of 'E' and the electron gain enthalpy of the other element, the more ionic the bond will be.

Step 3: Analyze electron gain enthalpy values.
Electron gain enthalpy values (in kJ mol⁻¹):
A = −328
B = −349
C = −325
D = −295

A more negative value means a stronger tendency to gain electrons. However, when the electron gain enthalpy is less negative (e.g., D = −295), the element is less electronegative, and thus, the bond formed will be more ionic (since the difference in electronegativity between E and D is larger).

Step 4: Determine the order of ionic character.
The ionic character decreases as electron gain enthalpy becomes more negative:
\[ \text{ED} > \text{EC} > \text{EB} > \text{EA} \]

Final Answer:
\[ \boxed{ED > EC > EB > EA} \]