Question #b8a3e

1 Answer
Oct 7, 2016

K_2Cr_2O_7

Explanation:

Assume you have 100g of the compound.
Mass(K) = 26.57g
Mass(Cr) = 35g
Mass(O) = 38.07g

To find the chemical formula, we need to convert mass to moles, and we can do this using the molar mass of the elements, which is just the atomic mass of the element in grams.
Molar mass(K) = 39.10 gmol^-1
Molar mass(Cr) = 52 gmol^-1
Molar mass(O) = 16 gmol^-1

Divide the mass by the molar mass to get moles.
moles(K)=(26.57cancelg)/(39.1cancelgmol^-1)=0.68 mol
moles(Cr)=(35cancelg)/(52cancelgmol^-1)=0.67 mol
moles(O)=(38.07cancelg)/(16cancelgmol^-1)=2.38mol

Mole ratio of K:Cr:O is 0.68:0.67:2.38~~1:1:3.5=2:2:7.
The formula is thus K_2Cr_2O_7