Chemical Reaction

Step 1: Analyzing Statement (i)
- The reaction of hydrogen with fluorine is highly exothermic and occurs spontaneously even in the dark due to fluorine’s high reactivity.
- The reaction is: - Since fluorine is the most electronegative element, it reacts readily without requiring external activation energy.
Conclusion: Statement (i) is correct.
Step 2: Analyzing Statement (ii)
- The Haber process for ammonia synthesis:
has an exothermic enthalpy change ( ). - Since ammonia formation releases heat, it is not endothermic.
Conclusion: Statement (ii) is incorrect.
Step 3: Analyzing Statement (iii)
- HF (hydrofluoric acid) is an electron-rich hydride because:
- It has three lone pairs on fluorine.
- It forms strong hydrogen bonds due to high electronegativity.
Conclusion: Statement (iii) is correct.
Step 4: Final Answer
Since statements (i) and (iii) are correct, the correct answer is:

We need to determine in which of the given reactions hydrogen ( ) is produced as a product.

Step 1: Analyze each reaction
1. Reaction i: Sodium borohydride reacts with iodine to release molecular hydrogen ( ) as one of the products: Thus, hydrogen is produced in this reaction. 2. Reaction ii: This reaction does not produce hydrogen. Instead, it forms sodium tetrafluoroborate. 3. Reaction iii: This reaction is a reduction process and does not yield hydrogen as a product. 4. Reaction iv: Diborane reacts with ammonia to form boron nitride and molecular hydrogen: Thus, hydrogen is produced in this reaction.

Step 2: Identifying the correct answer
From the above analysis, hydrogen is produced in reactions (i) and (iv). Thus, the correct answer is: