Carbon-14 and Uranium-238 have something we call a half live, which is basically a known time period for it to change half of its C-14 or U-238 radioactively decay. Since we know how long that is 5730 years for Carbon-14 for half a sample to deteriorate, than we can figure out how old it is.
When CaSO4 → Ca2+ + SO4
So when we have Ksp = [Ca2+][SO4]
when Ksp = 4.93 x 10^-5
and [SO4] = 0.02 M
so by substitution we can get [Ca2+]
4.93x10^-5 = [Ca2+] [0.02]
∴ [Ca2+] = 0.0025 mol/L
∴ the moles of calcium chloride = 0.0025 mol / L * 1.5 L
= 0.00167 mol
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