The molar heat capacity of solid aluminium is 24.4\text{ J K}^{-1}\text{ mol}^{-1} \text{ at } 25^{\circ}\text{C}24.4 J K −1 mol −1 at 25 ∘ C. What is the change in internal energy when 1\text{ mol}1 mol of solid aluminium is heated from a temperature of 20^{\circ}\text{C} \text{ to }30^{\circ}\text{C}20 ∘ C to 30 ∘ C?

Explanation:

The change in internal energy is given by the following expression:

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.