Naturally occurring zirconium exists are five isotopes. axe with a mass of 89.905 u(51.45%); zr with a mass of 90.906 u (11.22%); zr with a mass of 91.905 u (17.15%); zr with a mass of 93.906 u (17.38%) and zr with a mass of 95.908 u (2.80%). calculate the average mass of zirconium.

Isotope 1: 89.905 * 51.45 = 4625.61225 / 100 = 46.2561225
Isotope 2: 90.906 * 11.22 = 1019.96532 / 100 = 10.1996532
Isotope 3: 91.905 * 17.15 = 1576.17175 / 100 = 15.7617075
Isotope 4: 93.906 * 17.38 = 1632.08628 / 100 = 16.3208628
Isotope 5: 95.908 * 2.08 = 268.5424 / 100 = 2.685424

46.2561225 + 10.1996532 +  15.7617075 + 16.3208628 + 2.685424 = 91.22377
actual mass Zr = about 91.22

Answer( precipitate );