Copper exists in two naturally occurring isotopes. the average atomic weight of copper is 63.546 amu. if 69.15% exists as 63cu with an atomic mass of 62.92, then what is the atomic mass of the second isotope?

Answer is: the atomic mass of the second isotope is 64.95 amu (Cu-65).

Ar(Cu) = 63.546 amu; the average atomic weight of copper.

Ar(Cu-63) =62.92; he average atomic weight of copper-63.

ω(Cu-63) = 69.15% ÷ 100% = 0.6915.

ω(Cu-second isotope) = 100% - 69.15%.

ω(Cu-second isotope) = 30.85 % ÷ 100% = 0.3085.

Ar(Cu) = Ar(Cu-63) · ω(Cu-63) + Ar(Cu-second isotope) · ω(Cu-second isotope).

63.546 amu = 62.92 amu · 0.6915 + Ar(Cu-second isotope) · 0.3085.

Ar(Cu-second isotope) · 0.3085 = 63.546 amu - (62.92 amu · 0.6915).

Ar(Cu-second isotope) · 0.3085 = 20.037.

Ar(Cu-second isotope) = 20.037 ÷ 0.3085.

Ar(Cu-second isotope) = 64.95.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.