Answer:
In order to find a compound's empirical formula you must determine the smallest whole number ratio that exists between its constituent elements.
In this case, your unknown compound is said to contain only gold,
Au
, and oxygen,
O
. The compound's percent composition essentially tells you how many grams of each constituent element you get per
100 g
of compound.
In this case, a
100-g
sample of this unknown compound will contain
89.14 g
of gold and
10.86 g
of oxygen.
This means that you can use the molar mass of each element to find how many moles you get in that
100-g
sample. You will thus have
For Au:
89.14
g
⋅
1 mole Au
196.97
g
=
0.45256 moles Au
For O:
10.86
g
⋅
1 mole O
15.9994
g
=
0.67876 moles O
To find the mole ratio that exists between the two elements, divide both values by the smallest one. This will get you
For Au:
0.45256
moles
0.45256
moles
=
1
For O:
0.67876
moles
0.45256
moles
=
1.4998
≈
1.5
Now, it's important to remember that you're looking for the smallest whole number ratio here, which means that you're going to have to multiply both values by
2
to get
(
Au
1
O
1.5
)
2
⇒
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
Au
2
O
3
a
a
∣
∣
−−−−−−−−−−
Explanation:
