Question

The reaction energy of a reaction is the amount of energy released by the reaction. It is found by determining the difference in mass between the reactants and products and then using E=mc2 to convert the lost mass into the released energy. Look again at the equation for the decay of radium (Ra), given in the introduction. Use the following table of masses to determine the reaction energy of this reaction.Nucleus or particle Mass in atomic mass unitsradium-226 226.025402radon-222 222.017571alpha particle 4.002602Express your answer in joules to three significant figures.

Answer 1

Answer: the correct answer is 7.8026035971 x 10^(-13) joule

Explanation:

Use Energy Conservation. By ``alpha decay converts'', we mean that the parent particle turns into an alpha particle and daughter particles. Adding the mass of the alpha and daughter radon, we get

m = 4.00260 u + 222.01757 u = 226.02017 u .

The parent had a mass of 226.02540 u, so clearly some mass has gone somewhere. The amount of the missing mass is

Delta m = 226.02540 u - 226.02017 u = 0.00523 u ,

which is equivalent to an energy change of

Delta E = (0.00523 u)*(931.5MeV/1u)

Delta E = 4.87 MeV

Converting  4.87 MeV to Joules

1 joule [J] = 6241506363094 mega-electrón voltio [MeV]

4 mega-electrón voltio = 6.40870932 x 10^(-13) joule

4.87 mega-electrón voltio = 7.8026035971 x 10^(-13) joule