Answer to Question #2662 in Physical Chemistry for ryan

Question

Three helium nuclei fuse together, forming one carbon nucleus. The mass of carbon is less than
three times the mass of helium. When helium fuses into carbon, which of the following occurs?
a. Rest‐mass energy is converted into some other form of energy
b. Some other form of energy is converted into rest‐mass energy
c. The chemical reaction changed the total mass
d. The mass of three helium nuclei turned into one carbon nucleus and other smaller
particles, such as protons and neutrons.

Answer 1

Since the mass of the 3 helium nuclei together do not give the mass of a carbon nucleus, this means that some of the mass of the helium went somewhere. One of the consequences of Einstein's special theory of relativity (1905) is that the mass of an object increases with its velocity relative to the observer. When an object is at rest (relative to the observer), it has the usual (inertial = tendency to resist an applied force) mass that we are all familiar with. This is called the 'rest mass' of the object.

So the answer is
a. Rest mass energy is converted into some other form of energy