doggo123
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#1
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#1
The relative atomic mass of neon is 20.18. It consists of 3 isotopes, 20Ne, 21Ne and 22Ne. It contains 90.5% 20Ne. Find the percentage composition by mass of the other two isotopes in neon.
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classifyed98
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Take the % of 21Ne to be x and % of 22Ne to be y.
Now form 2 equations.
if 20Ne is 90.5%, then the sum of the others' percentages will be (100-90.5)% = 9.5%
so:
x+y = 9.5

second equation:
Ar = 20.18 = ( (20*90.5)+(21*x)+(22*y) )/100 = 20.18

Just solve for x and y.
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doggo123
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#3
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#3
(Original post by classifyed98)
Take the % of 21Ne to be x and % of 22Ne to be y.
Now form 2 equations.
if 20Ne is 90.5%, then the sum of the others' percentages will be (100-90.5)% = 9.5%
so:
x+y = 9.5

second equation:
Ar = 20.18 = ( (20*90.5)+(21*x)+(22*y) )/100 = 20.18

Just solve for x and y.
Thank you so much!
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Oliver Knightley
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#4
Report 4 months ago
#4
(Original post by doggo123)
The relative atomic mass of neon is 20.18. It consists of 3 isotopes, 20Ne, 21Ne and 22Ne. It contains 90.5% 20Ne. Find the percentage composition by mass of the other two isotopes in neon.
Neon has RAM of 20.18
Isotope (20)Ne has 90.5% abundance
Neon also has isotopes (21)Ne and (22)Ne

Find the % abundance of all of Neon’s isotopes

Step 1: Find the remaining % abundance:

1-0.905 = 0.095

Step 2: Turn question into algebraic equation:

(20)(0.905)+(21)(X) + (22)(0.095-X)=20.18

step 3: Rearrange to make X the subject:

(20)(0.905) = 18.1

(21)(X) = 21X

(22)(0.095-X) = 2.09 - 22X

18.1+2.09-20.18=22X - 21X

0.01 = X

Step 4: Now use X to find the % abundance of isotope 21Ne and 22Ne

0.095 - 0.01 = 0.085

Step 5: Make sure all the % abundance of each isotope adds up to 1 (or 100%)

90.5% + 1% + 8.5% = 100%

0.01 + 0.085 + 0.905 = 1

Step 6: format your answer by listing each isotope with their corresponding abundance

20Ne = 90.5%

21Ne = 1%

22Ne = 8.5%
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Oliver Knightley
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#5
Report 4 months ago
#5
(Original post by classifyed98)
Take the % of 21Ne to be x and % of 22Ne to be y.
Now form 2 equations.
if 20Ne is 90.5%, then the sum of the others' percentages will be (100-90.5)% = 9.5%
so:
x+y = 9.5

second equation:
Ar = 20.18 = ( (20*90.5)+(21*x)+(22*y) )/100 = 20.18

Just solve for x and y.
y will be equal to 0.095 - x so you only need to solve for x, it may be easier this way
Last edited by Oliver Knightley; 4 months ago
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