Question #86b83

1 Answer
Mar 21, 2017

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:

# 44g -: 16 g/"mol" = 2.75# mol

Now, since the formula is #X_2O_5#, we now that for each 5 moles of O there are 2 moles of X, a #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 #"molar mass" = "mass"/"moles" = 56/1.1 = 50.9# g per mole.

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