Step 1: Understanding the Concept
ATP is formed from ADP and inorganic phosphate in an energy-requiring reaction.
Step 2: Energy value
The terminal high-energy phosphate bond stores about 7.3 kcal per mole. This is the same energy released when ATP is hydrolysed to ADP and Pi.
Step 3: Conclusion
The missing value is 7.3.
Final Answer:
The missing energy is 7.3 kcal.
\[ \boxed{\text{(C) }7.3} \]