Question

Choose the correct statement about para & ortho Hydrogen A. Total spin of ortho hydrogen is zero.
B. Total spin of para hydrogen is zero.
C. The physical properties of two forms are different.
D. The chemical properties of two forms are different.
E. At higher temperature ortho is more stable. Choose the correct answer from the options given below:

• A. A, C, E only
• B. B, D, E only
• C. B, C, E only
• D. A, D, E only

Hint:

Logic Tip: Para hydrogen has opposite nuclear spins (total spin = 0), while ortho hydrogen has parallel spins (total spin = 1). Physical properties differ, but chemical properties are nearly identical.

Answer 1

The Correct Option is C

Concept:
Hydrogen exists in two spin isomeric forms:
• Ortho-hydrogen: nuclear spins are parallel
• Para-hydrogen: nuclear spins are antiparallel
Step 1:
In ortho-hydrogen: \[ \text{Total nuclear spin}=1 \] In para-hydrogen: \[ \text{Total nuclear spin}=0 \] Hence:
• Statement A is incorrect
• Statement B is correct
Step 2:
Ortho and para hydrogen differ in:
• Heat capacity
• Boiling point
• Thermal conductivity Therefore, physical properties are different. So, statement C is correct.
Step 3:
Their chemical properties are almost identical because both contain the same hydrogen atoms and bonding. Hence statement D is incorrect.
Step 4:
At higher temperatures, ortho-hydrogen becomes more stable and predominant. Thus statement E is correct. \[ \boxed{\text{Correct Option = (3) B, C, E only}} \]