Hi,
A few of my friends and I were discussing the attached question and we're a bit confused as to how to find the mass defect for part b.
The worked solution (attached) says that four protons combine to form a helium nucleus, and calculate the mass defect and thus energy released accordingly. However, four protons don't combine to form just a helium nucleus - to balance the equation it appears that two positrons should also be released, so we don't know whether this should also be included in the mass defect equation.
Alternatively, we've been taught that mass defect is the mass of the constituents - the mass of the nucleus, which seems to suggest that we do the mass of 2 protons and 2 neutrons - the mass of the nucleus, then calculate energy using E=mc2. However, this renders a different answer.
Which approach is correct?
Thank you.