[填空题]
Estimate the number of (afo6wvr3cc, n v /8cgh() mo0o9j tz 8lq;anles, $ \times10^{22 }$ moles and (b) molecules of water in all the Earth’s oceans. Assume water covers 75% of the Earth to an average depth of 3 km. $\approx$ $ \times10^{46 }$ molecules