Chemistry- figuring out the formula from the systematic name

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chocochip_
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Say we are given Sodium Nitrate (V) how would you deduce the molecular formula of this?
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jsg9
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The (V) refers to the oxidation state of the N in the compound because it comes at the end of the name, if the (V) were just after sodium, that would refer to the oxidation state of sodium in the compound.

Oxygen has an oxidation state of -2 unless it's in hydrogen peroxide, and there are 3 oxygen atoms, so the oxygen in the compound gives a total of -6. Na has an oxidation state of +1 as it's in group 1 of the periodic table. N has a +5 oxidation state as worked out from the name. A compound should have a sum of oxidation states of all atoms equal to 0: (-6) + 5 + 1 = 0. So you have NaNO3. It took 1 Na atom, 1 N atom and 3 O atoms to give an overall oxidation state of 0, working backwards from knowing the oxidation state of N was +5. So your molecular formula is NaNO3.
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