Final answer:
The percentage natural abundances of Lithium isotopes are calculated using the isotopic masses and the expected average atomic mass. Lithium-6 has an abundance of 7.52%, and Lithium-7 has an abundance of 92.48%.
Step-by-step explanation:
To calculate the percentage natural abundances of the isotopes of Lithium, we use the given isotopic masses and abundances to determine the average atomic mass of lithium. We have the following isotopes: Lithium-6 (with a mass of 6.01512 amu and abundance x%) and Lithium-7 (with a mass of 7.01600 amu and abundance (100-x)%). The average atomic mass of lithium is known and can be looked up on the periodic table. Assuming it to be around 6.94 amu (as this is a standard value), we can set up the equation:
(6.01512 × x/100) + (7.01600 × (100-x)/100) = 6.94
By rearranging and solving for x, we find that x is approximately 7.5, which means the abundance of Lithium-6 is 7.5%, and the abundance of Lithium-7 is 92.5%. However, when rounded to two decimal places, the abundances of Lithium-6 and Lithium-7 are roughly 7.52% and 92.48%, respectively. So the correct answer from the provided options is (a) 7.52% and 92.48%.