# E = mc2 - mass energy conversion

Q1.

(a) State what is meant by the binding energy of a nucleus.

(2 marks)

(b)

(i) The iron isotope (atomic mass: 55.93493) has a very high binding energy per nucleon. Calculate its value in MeV.

Use the following data:

mass of proton = 1.00728 u

mass of neutron = 1.00867 u

(ii) If the isotope were assembled from its constituent particles, what would be the mass change, in kg, during its formation?

(6 marks)

(Total 8 marks)

Q2.

(a) In the context of an atomic nucleus,

(i) state what is meant by binding energy, and explain how it arises,

(ii) state what is meant by mass difference,

(iii) state the relationship between binding energy and mass difference.

(4 marks)

(b) Calculate the average binding energy per nucleon, in MeV nucleon–1, of the nucleus..

mass of atom = 63.92915 u

mass of proton = 1.00728 u

mass of neutron = 1.00867 u

mass of electron = 0.00055 u

(5 marks)

(c) Why would you expect the zinc nucleus to be very stable?

(1 marks)

(Total 10 marks)

Q3. Nuclei of Po decay by the emission of an α particle to form a stable isotope of an element X. You may assume that no γ emission accompanies the decay.

(a)

(i) State the proton number of X.

(ii) State the nucleon number of X.

(2 marks)

(b) Each decaying nucleus of releases 8.6 × 10–13 J of energy.

(i) State the form in which this energy initially appears.

(ii) Using only the information provided in the question, calculate the difference in mass between the original polonium atom and the combined mass of an atom of X and an α particle.

speed of light in vacuum = 3.0 × 108 ms–1

(3 marks)

(Total 5 marks)

Q4.

(a)

(i) Copy and complete the equation below to represent the emission of an α particle by a isotope.

(ii) Calculate the energy released when a isotope nucleus emits an alpha particle

mass of uranium 238 nucleus: 238.05076 u

mass of an alpha particle: 4.00260 u

mass of thorium 234 nucleus: 234.04357 u

(5 marks)

(b) decays sequentially by emitting α particles and β particles, eventually forming , a stable isotope of lead.

(i) There are eight alpha particles in the sequence. Calculate the number of beta- particles in the sequence.

(ii) State the nuclear change that occurs during positron emission. Hence, explain why no positrons are emitted in this sequence.

(6 marks)

(Total 11 marks)