Question

The mass of the ocean is about `1.8 x 10^21 kg`. If the ocean contains 1.076% by mass sodium ions, `Na^+`, what is the mass in kilograms of `Na^+` in the ocean?

Answer 1

There are `1.8xx10^21*kgxx1.076%` `kg` of sodium ions.

Explanation:

Because `1.076%` `~=` `10^-2`, there are thus at least a `1.8xx10^21*kgxx10^-2` mass of sodium ions, i.e. `=` `1.8xx10^19*kg`, which is not an inconsiderable quantity.