Copper used in electric wires comes in two flavors (isotopes): 63cu and 65cu. 63cu has
an atomic mass of 62.9298 amu and an abundance of 69.09%. the other isotope, 65cu.
has an abundance of 30.91%. the average atomic mass between these two isotopes is
63.546 amu. calculate the actual atomic mass of 65cu.

answer:

) copper used in electric wires comes in two flavors (isotopes): 63cu and65cu. 63cu

explanation:

has an   atomic mass of 62.9298 amu and an abundance of 69.09%. the other

isotope, 65cu, has an abundance of 30.91%. the average atomic mass between

these two isotopes is 63.546 amu

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

a:

by the combination of an unlimited number of elements