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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