Naturally occurring iodine has an atomic mass of 126.9045. A 12.3849 -g sample of iodine is accidentally contaminated with 1.00070 g of ^129 I, a synthetic radioisotope of iodine used in the treatment of certain diseases of the thyroid gland. The mass of ^129 I is 128.9050amu.
Find the apparent "atomic mass" of the contaminated iodine.
127.055 amu
127.055 amu
oops, all that has to be divided by the total mass, 12.3849 g
To find the apparent "atomic mass" of the contaminated iodine, we need to take into account the mass of both naturally occurring iodine and the synthetic radioisotope iodine (^129 I).
First, we calculate the mass of naturally occurring iodine in the sample by subtracting the mass of ^129 I from the total mass of the sample:
Mass of naturally occurring iodine = Total mass of sample - Mass of ^129 I
Mass of naturally occurring iodine = 12.3849 g - 1.00070 g
Mass of naturally occurring iodine = 11.3842 g
Next, we calculate the total mass of iodine in the sample by adding the mass of naturally occurring iodine and the mass of ^129 I:
Total mass of iodine = Mass of naturally occurring iodine + Mass of ^129 I
Total mass of iodine = 11.3842 g + 1.00070 g
Total mass of iodine = 12.3849 g
Finally, we calculate the apparent "atomic mass" of the contaminated iodine by dividing the total mass of iodine by the number of moles of iodine in the sample:
Apparent "atomic mass" = Total mass of iodine / Number of moles of iodine
To find the number of moles of iodine, we divide the total mass of iodine by the molar mass of iodine:
Number of moles of iodine = Total mass of iodine / Molar mass of iodine
The molar mass of iodine is the atomic mass of naturally occurring iodine, which is given as 126.9045 amu:
Number of moles of iodine = 12.3849 g / 126.9045 g/mol
Number of moles of iodine ≈ 0.0973 mol
Now, we can calculate the apparent "atomic mass" of the contaminated iodine:
Apparent "atomic mass" = 12.3849 g / 0.0973 mol
Apparent "atomic mass" ≈ 127.3128 g/mol
Therefore, the apparent "atomic mass" of the contaminated iodine is approximately 127.3128 g/mol.
avg atomic mass=
1.00070*128.9050 +(12.3849-1.00070)126.9045