What is the molar mass of copper (Cu)
The correct answer and explanation is:
The molar mass of copper (Cu) is approximately 63.546 grams per mole.
Copper is a chemical element with the atomic number 29, meaning each atom of copper contains 29 protons. The molar mass represents the mass of one mole of copper atoms, which is the amount of substance containing Avogadro’s number (about 6.022 × 10²³) of atoms. The value 63.546 g/mol reflects the weighted average of the masses of copper’s naturally occurring isotopes.
Copper has two primary stable isotopes: copper-63 and copper-65. Copper-63 has an atomic mass of about 62.9296 atomic mass units (amu), and copper-65 has an atomic mass of about 64.9278 amu. The natural abundance of copper-63 is approximately 69.15%, while copper-65 makes up roughly 30.85%. The molar mass is calculated by taking these isotope masses and their relative abundances into account.
The calculation follows this formula:
Molar mass = (mass of Cu-63 × fraction of Cu-63) + (mass of Cu-65 × fraction of Cu-65)
Substituting the values:
Molar mass = (62.9296 amu × 0.6915) + (64.9278 amu × 0.3085)
Molar mass ≈ 43.51 + 20.04
Molar mass ≈ 63.55 amu (rounded to 63.546 g/mol for precision)
Since the atomic mass unit (amu) is numerically equivalent to grams per mole in molar mass terms, this value gives the molar mass in grams per mole.
This molar mass is essential in chemistry because it allows conversion between the number of moles of copper atoms and the mass in grams. It is used in stoichiometry calculations in reactions involving copper, in determining concentrations, and in various applications across materials science, metallurgy, and electronics.
In summary, the molar mass of copper is about 63.546 g/mol, reflecting the weighted average of its isotopes’ masses according to their natural abundances.