Which of the statements are true? select all that apply. a) the entropy at the start of a reaction is always greater than the entropy of the products. b) the amount of usable energy resulting from a reaction is always less than the total energy available at the start of the reaction. c) the entropy of the products of a reaction is always greater than the entropy at the start of the reaction. d) the energy for a reaction equals the sum of the energy in the product plus energy released as heat and disorder.

b. The amount of usable energy resulting from a reaction is always less than the total energy available in the starting materials.

d. The energy of the starting materials for a reaction equals the sum of the product energies plus energy released as heat and disorder.

Explanation:

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b. The amount of usable energy resulting from a reaction is always less than the total energy available in the starting materials.  

In this case, since during the chemical reaction there was a rearrangement of the molecules due to the chemical change, there was a wasted energy for this process, thus, that will be unusable energy after the reaction finishes.

d. The energy of the starting materials for a reaction equals the sum of the product energies plus energy released as heat and disorder.

In this case, an energy balance help us substantiate it:

Since during a chemical reaction, the difference between the reagents and products is defined by the implied change that separate them after the reaction is complete.

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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.