1. “what forms of energy conversions occur during the process of photosynthesis? (How does energy transform?) 2. What is missing from the food web but is essential to maintain equilibrium? A. Soil B.water C. Decomposers D. Oxygen
Answer:
The standard enthalpy of formation of HgO is -90.7 kJ/mol.
Explanation:
The reaction between Hg and oxygen is as follows.

From the given,
Molar mass of HgO = 216.59 g/mol
Mass of HgO decomposed = 18.5 g
Amount of heat absorbed = 7.75 kJ
From the reaction,
The standard enthalpy of formation = 
During the decomposition of 1 mol of HgO , 90.7 kJ of energy absorbed.
For the formation of 1 mol of HgO , 90.7 kJ of energy is release
Therefore, the enthalpy of formation of mercury(II)Oxide is -90.7 kJ/mol
It seems like the answer is C, you really just need to use the process of elimination.
120.38 g/mol is the answer