What energy must be added or given off in a reaction where two hydrogen atoms and two neutrons are combined to form a helium atom? (Atomic masses for each: hydrogen,1.007 825 u;neutron,1.008 665 u;helium,4.002 602 u;also,1 u = 931.5 MeV/c²) A)74.85 MeV added B)74.85 MeV given off C)28.30 MeV given off D)28.30 MeV added

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The mass defect in the reaction is calculated by subtracting the mass of the helium atom from the combined mass of the hydrogen atoms and neutrons. This mass defect is then converted to energy using E=mc², resulting in 28.30 MeV being given off.

What Energy Must Be Added or Given Off in a Reaction