Which net change occurs in a nuclear fusion
reaction?
(1) ionic bonds are broken.
(2) ionic bonds are formed.
(3) energy is converted to mass.
(4) mass is converted to energy.

Correct  (4) Mass is converted to energy.

Reason: 
In a nuclear fusion reaction, two small nuclei are fused to formed a relatively heavy nuclei. The mass of the daughter nuclear is less as compared to parent nuclei. This difference is mass is converted into energy. The energy liberated during this process can be estimated by the Einstein's equation i.e. E = m.  

Answer : option c) heat is released during the process.explanation :

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

What are the options? i can you if you give them.