Naturally occurring copper exists as two isotopes, 63Cu and 65Cu - VCE - SSCE Chemistry - Question 16 - 2004 - Paper 1
Question 16
Naturally occurring copper exists as two isotopes, 63Cu and 65Cu. The relative atomic mass of copper is 63.6.
The ratio of 63Cu to 65Cu in natural copper is approxim... show full transcript
Worked Solution & Example Answer:Naturally occurring copper exists as two isotopes, 63Cu and 65Cu - VCE - SSCE Chemistry - Question 16 - 2004 - Paper 1
Step 1
Calculate the contribution of each isotope
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Given the relative atomic mass of copper is 63.6, we can denote the fractions of 63Cu and 65Cu as x and y, respectively.
Using the equation for the average atomic mass:
x×63+y×65=63.6
Since these are the only two isotopes, we also have:
x+y=1
Now, substituting y with (1 - x) gives:
x×63+(1−x)×65=63.6
Step 2
Solve the equations
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Expanding that, we get:
63x+65−65x=63.6
Combining like terms gives:
−2x+65=63.6
Thus:
−2x=63.6−65−2x=−1.4x=0.7
Now substituting back to find y:
y=1−x=1−0.7=0.3
Step 3
Determine the ratio
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Now that we have x and y, we find the ratio of 63Cu to 65Cu:
Ratio=yx=0.30.7=37
This simplifies to approximately 3:1.
Step 4
Final answer
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Thus, the ratio of 63Cu to 65Cu in natural copper is approximately 3:1, which corresponds to option D.
