Discussion

How many moles of iron are there in 122 of Fe ? (MW of iron is 55.858)

Answer: C

122 g of iron is 2.18 mol Fe.

The number of moles is mass divided by molar mass (the paper prints '122 of Fe', meaning 122 g):

\[ n = \frac{122}{55.858} \approx 2.18\ \text{mol} \]

As a check, 2 mol of iron is about 111.7 g and 2.2 mol about 122.9 g, so 122 g lies just below 2.2 mol.

1.28 and 1.18 mol would weigh only about 66 to 72 g, and 8.12 mol would be about 454 g.

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