SOMEONE ASKED ๐
a chloride of rhenium contains 63.6 % rhenium. WHat is the formula of this compound?
HERE THE ANSWERS ๐

Imagine that you have 100 grams of the compound. It would have 63.6 grams of Rhenium and 36.4 grams of Chlorine.
Convert each of those masses into moles by dividing each by its molar mass, and then find the simplest ratio of moles:
63.6 g Re / 186.2 g/mol = 0.34 mol Re
36.4 g Cl / 35.45 g/mol = 1.03 mol Cl
Divide both numbers of moles by 0.34 (the smaller one):
0.34/0.34 = 1 mol Re
1.03/0.34 = 3 mol Cl
THe formula is ReCl3

You can ask yourself if containing is what you really want by 63.6 % rhenium

OK, this is algebra basically.
Your unknown formula is Re(x)Cl(y)
The MW of Re is 186.2 and the MW of Cl is 35.5
So, x * 186.2 is the part of the MW that is due to Re and
(186.2 x) + (35.5 y) it the total MW
So we know that
(186.2)(x)/[(186.2)x) + (35.5)(y) ] = 0.636
So, cross multiply using (0.636/1) to get
186.2x = 0.636*(186.2x + 35.5y) now distribute
186.2x = 118.4x + 22.6y now combine x terms
67.8x = 22.6 y now divide by 22.6
3x = y
So there are 3x as many Cl molecules as Re
Check your answer: ReCl3 = (186.2 + 3*35.5) = 292.7 MW What is the % Re?
186.2/292.7 = 63.6%
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