Chalcopyrite, the principal ore of copper (cu), contains 34.63 percent cu by mass. how many atoms of cu can be obtained from 5.11 x 103 kg of ore? a) 1.68 x 1028 cu atoms b) 1.68 x 1025 cu atoms c) 6.77 x 1031 cu atoms d) 6.77 x 1034 cu atoms

A) 1.68 x 10²⁸ Cu atoms.

Explanation:

∵ The mass of Cu in the chalcopyrite ore = mass of the ore x weight fraction of Cu.

∴ The mass of Cu in the chalcopyrite ore = mass of the ore x weight fraction of Cu = (5.11 x 10³ kg)(0.3463) = 1.77 x 10³ kg.

n of Cu = mass/atomic mass of Cu = (1770 x 10³ g) / (63.54 g/mol) = 27.853 x 10³ mol.

∴ 27.853 x 10³ mol of Cu contains = (27.853 x 10³ mol)(6.022 x 10²³) = 1.677 x 10²⁸ Cu atoms ≅ 1.68 x 10²⁸ Cu atoms.

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.