The formula for rust can be represented by Fe 2 O 3 . How many moles of Fe are present in 21.3g...

Question:

The formula for rust can be represented by Fe{eq}_2 {/eq}O{eq}_3 {/eq}. How many moles of Fe are present in 21.3g of the compound?

Moles of atoms in compounds:

The molar ratios between atoms in a compound and the molar amount of the compound itself work exactly the same as molar ratios between compounds in a balanced equation. For example, in 1 mole of {eq}CO_2 {/eq} there is 1 mole of carbon atoms and 2 moles of oxygen atoms.

Answer and Explanation:

{eq}Fe_2O_3 {/eq} has a molar mass of 159.69g/mol. We divide mass by molar mass to get moles:

21.3g / 159.69g/mol = 0.133mol

For every mole of {eq}Fe_2O_3 {/eq} there are 2 moles of iron, hence there will be 0.133mol x 2 = 0.266mol of iron present.


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Mole-to-Mole Ratios and Calculations of a Chemical Equation

from Chemistry 101: General Chemistry

Chapter 9 / Lesson 2
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