Question

what is the average atomic weight for copper

Answer 1

AVERAGE ATOMIC MASS = PERCENTAGE OF ONE ISOTOPE * THIS ISOTOPE'S MASS
+
PERCENTAGE OF OTHER ISOTOPE * THIS ISOTOPE'S MASS
+.............................. (SUM OF ALL PERCENTAGE SHOULD BE 100)

one ISOTOPE of COPPER have mass of 62.93 amu and composes 69.2%
other ISOTOPE of COPPER have mass of 64.93 amu and composes 30.8%


AVERAGE ATOMIC MASS (copper)= PERCENTAGE OF ONE ISOTOPE * THIS ISOTOPE'S MASS
+

PERCENTAGE OF OTHER ISOTOPE * THIS ISOTOPE'S MASS




= (69.2% * 62.93 amu) + (30.8% * 64.93 amu)


= (69.2 / 100 * 62.93 amu) + (30.8 / 100 * 64.93 amu)

= (4354.756 / 100 amu) + (1980.44 / 100 amu)

= 43.54756 amu + 19.8044 amu

= 63.35196 amu