Question

If the first ionisation enthalpy of Li, Be and C respectively are 520, 899, 1086 kJ/mol, the first ionisation enthalpy (in kJ/mol) of B will be

• A. 487
• B. 950
• C. 801
• D. 1402

Hint:

The ionisation enthalpy generally increases across a period from left to right.

Answer 1

The Correct Option is C

Step 1: Ionisation enthalpy generally increases across a period from left to right. From the given values, we observe that the ionisation enthalpy of Li is 520 kJ/mol, Be is 899 kJ/mol, and C is 1086 kJ/mol. 

Step 2: The ionisation enthalpy of B, being between Be and C, will likely be between 899 and 1086 kJ/mol. The most reasonable estimate for B's ionisation enthalpy is 801 kJ/mol.

Step 3: This follows the trend of increasing ionisation enthalpy across the period. Thus, the correct value of the first ionisation enthalpy of B is closest to 801 kJ/mol.