Question #b7ed9

1 Answer
Fleur
Oct 22, 2017

#"0.051 mol Co"#

Explanation:

There is no formula—all you need is the Periodic Table!

The Periodic Table indicates that there are about #"58.933 grams"# of cobalt in #"1 mole"# of it.

Thus, we can use the conversion factor #"58.933 g Co" / "1 mol Co"# or #"1 mol Co" / "58.933 g Co"#. In this case, we use the second one so that the #"g"# unit cancels out.

#"3.0" cancel("g Co") xx "1 mol Co" / ("58.933" cancel("g Co")) = "0.051 mol Co"#

Since the given information has only two significant figures, that's what we round to.

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