# Question 86b83

Mar 21, 2017

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

#### Explanation:

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:

$44 g \div 16 \frac{g}{\text{mol}} = 2.75$ mol

Now, since the formula is ${X}_{2} {O}_{5}$, we now that for each 5 moles of O there are 2 moles of X, a $\frac{2}{5}$ 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" = "mass"/("molar mass")

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

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