An ore is a rock that contains which of the following? a. a mineral or metal with economic usefulness b. a gemstone only c. a mineral or metal with no practical use d. particles of rock that erode into sediment

The correct answer is option A. "a mineral or metal with economic usefulness".

Explanation:

An ore is defined as a rock or sediment found in nature which contains a mineral or metal with economic usefulness. The minerals or metals in the ore must be extracted before they could be used, and typically, they are refined via smelting. The ore grade is defined according to the concentration of the mineral or metal beneath the rock or sediment.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.