A chemistry problem.. No idea how to solve.. PLEASE HELP!!!?

S

sportegirl7

New member
1) The element chronium has four naturally occuring isotopes. Use the relative abundance of each to calculate the average atomic mass of chromium..

50Cr= 4.34%, 52Cr= 83.79%, 53Cr= 9.50%, 54Cr= 2.37%

BTW i would really appreciate it if you guys walked me through the steps on how to solve this problem... Instead of just giving me the answer.. Thanks!!!!!!
 
50Cr= 4.34%, 52Cr= 83.79%, 53Cr= 9.50%, 54Cr= 2.37%
4.34 x 50 = 217
83.79 x 52 = 4357.08
9.5 x 53 = 503.5
2.37 x 54 = 127.98

total = 5205.56
devide by 100 = 52.0556
answer 52
 
With each isotope, there's a corresponding atomic mass. It's based on the amount of neutrons in the isotope, so just look those up in a book or online, or you can calculate it based on the amount of neutrons and protons in the nucleus and the mass of each.
Then, you multiply the percentages by each corresponding mass. Make sure you do the percentages as decimals (4.34% = .0434).
And then add them all up to get the average atomic mass.
 
the atomic number of chromium is 24 meaning each atom contains 24 protons and 24 electrons and enough neutrons to equal the atomic weight of each isotope:

50Cr atoms have 24 protons, 24 electrons and 26 neutrons
52Cr atoms have 24 protons, 24 electrons and 28 neutrons
53Cr atoms have 24 protons, 24 electrons and 29 neutrons
54Cr atoms have 24 protons, 24 electrons and 30 neutrons

Note: 52Cr has an atomic mass of 51.940510 and each neutron has an atomic mass of 1.008665, so you can add/subtract multiples of this number to get the atomic masses of 50Cr, 53Cr and 54Cr.

Calculate the weights of the individual isotopes and average them according to the relative abundances:

(AtWt of 50Cr) x (0.0434) +
(AtWt of 52Cr) x (0.8379) +
(AtWt of 53Cr) x (0.0950) +
(AtWt of 54Cr) x (0.0237) =

Average Atomic weight of Chromium which is about 51.9961%
 
Back
Top