Question

Zinc has three major and two minor isotopes. For this problem, assume that the only isotopes of zinc are the major ones, zinc-64, zinc-66, and zinc-68. The atomic mass of zinc-64 is 63.9291 Da, that of zinc-66 is 65.9260 Da, and that of zinc-68 is 67.9248 Da. Calculate the atomic mass of zinc from the relative peak intensities in the following spectrum. peak intensity for zinc 64 = 100 peak intensity for zinc 66 = 57.4 peak intensity for zinc 68 = 38.6

Answer 1

The atomic mass of Zinc is 65.30 Da

Step-by-step explanation:

Step 1: Data given

3 major isotopes

⇒ Zinc-64

atomic mass = 63.929 Da

Peak intensity = 100

⇒ Zinc-66

atomic mass = 65.9260 Da

Peak intensity = 57.4

⇒ Zinc- 68

atomic mass = 67.9248 Da

Peak intensity = 38.6

Step 2: Calculate the natural abundance

∑peak intensity = 100 + 57.4 + 38.6 = 196

Zinc-64 : 100/196 = 0.5102 ⇒ 51.02 %

Zinc-66 : 57.4/196 = 0.2929 ⇒ 29.29 %

Zinc-68 : 38.6/196 = 0.1969 ⇒ 19.69 %

Step 3: Calculate the atomic mass if Zinc

63.9291 * 0.5102 + 65.9260*0.2929 + 67.9248*0.1969 = 65.3007 Da

The atomic mass of Zinc is 65.30 Da