Final answer:
The atomic mass of the other isotope of lithium is approximately 7.017 amu, calculated based on the average atomic mass of lithium (6.94 amu) from the periodic table and the given isotopic composition.
Step-by-step explanation:
To determine the atomic mass of the other stable isotope of lithium, we will use the average atomic mass of lithium and the given information about the isotopic composition.
The average atomic mass of lithium can be found on the periodic table, and it is typically about 6.94 amu.
Now, if 30 out of 400 lithium atoms are lithium-6 (mass of 6.015 amu), then 370 atoms are of the other isotope.
Let's call the atomic mass of the other isotope x amu.
The average atomic mass (A) can be calculated using the formula:
A = (fraction of Li-6 * atomic mass of Li-6) + (fraction of the other isotope * atomic mass of the other isotope)
Plugging the values we get:
6.94 amu = (30/400 * 6.015 amu) + (370/400 * x amu)
Solving for x, we first calculate the contribution from lithium-6, which is:
30/400 * 6.015 amu = 0.451125 amu
Subtracting this from the average atomic mass:
6.94 amu - 0.451125 amu
= 6.488875 amu
This is the total contribution from the other isotope.
To find the atomic mass of one atom of the other isotope, we divide this by the fraction of those atoms:
6.488875 amu / (370/400) = 7.017 u (rounded to three decimal places)
Therefore, the atomic mass of the other isotope of lithium is approximately 7.017 amu.