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Answer 1 · 2017-03-21T17:01:15

Element X is vanadium. Here's how we know...

Start by assuming we have 100 g of this compound. That way, the percentages translate directly into masses: 44 g of O and 56 g of X.

Now, calculate the moles of oxygen:

$44 g \div 16 \frac{g}{mol} = 2.75$ $44g -: 16 g/"mol" = 2.75$ mol

Now, since the formula is $X_{2} O_{5}$ $X_2O_5$ , we now that for each 5 moles of O there are 2 moles of X, a $\frac{2}{5}$ $2/5$ ratio.

Since there is actually 2.75 moles of O, there must be #2.75 xx 2/5 = 1.1 moles of X.

Since 1.1 mole of X has a mass of 56 g, the molar mass of X must be

$moles = \frac{mass}{molar mass}$ $"moles" = "mass"/("molar mass")$

or $molar mass = \frac{mass}{moles} = \frac{56}{1.1} = 50.9$ $"molar mass" = "mass"/"moles" = 56/1.1 = 50.9$ g per mole.

Looking at the periodic table, we see it must be vanadium.