Determine the mass of 7.20 moles of iron??

Explanation:

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In this case, since the mole-mass relationships allows us to compute the moles or mass of a sample given the mass or moles via the atomic (elements) or molar mass (compounds). For iron, whose atomic mass is 55.847 g/mol, we can compute the mass o 7.20 moles as shown below:

As you can see we write 1 mol Fe on bottom in order to cancel the given moles out.

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answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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