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# Chemistry/Physics Question: atomic mass

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1. chlorine has two naturally occurring isotopes that exist in an almost 75:25 abundance ratio. The average relative atomic mass of chlorine is 35.5 what are the relative atomic masses of these two isotopes? find out their proton and nucleon number
2. Average relative atomic mass = (mass of isotope 1 x abundance%)+(mass of isotope 2 x abundance %) / 100
25% of one and 75% of the other
so 0.25 and 0.75 as abundances
35.5 = 0.25m1+0.75m2 (m1 = mass of isotope 1)
See if you can get it with that
3. That leads to m1+3m2=142 Two unknowns, one equation so can't solve.
Can't see how to get a second equation in m1 and m2 to solve...
4. (Original post by Blake Jones)
Average relative atomic mass = (mass of isotope 1 x abundance%)+(mass of isotope 2 x abundance %) / 100
25% of one and 75% of the other
so 0.25 and 0.75 as abundances
35.5 = 0.25m1+0.75m2 (m1 = mass of isotope 1)
See if you can get it with that
That leads to m1+3m2=142 Two unknowns, one equation so can't solve.
Can't see how to get a second equation in m1 and m2 to solve..

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