Answer:
[tex]\boxed {\boxed {\sf About \ 2.127 \ moles \ of \ FeCl_3}}[/tex]
Explanation:
To convert from moles to grams, the molar mass must be used.
1. Find Molar Mass
The compound is iron (III) chloride: FeCl₃
First, find the molar masses of the individual elements in the compound: iron (Fe) and chlorine (Cl).
There are 3 atoms of chlorine, denoted by the subscript after Cl. Multiply the molar mass of chlorine by 3 and add iron's molar mass.
This number tells us the grams of FeCl₃ in 1 mole.
2. Calculate Moles
Use the number as a ratio.
[tex]\frac{162.19 \ g \ FeCl_3}{1 \ mol \ FeCl_3}[/tex]
Multiply by the given number of grams, 345.0.
[tex]345.0 \ g \ FeCl_3 *\frac{162.19 \ g \ FeCl_3}{1 \ mol \ FeCl_3}[/tex]
Flip the fraction so the grams of FeCl₃ will cancel.
[tex]345.0 \ g \ FeCl_3 *\frac{1 \ mol \ FeCl_3}{162.19 \ g \ FeCl_3}[/tex]
[tex]345.0 *\frac{1 \ mol \ FeCl_3}{162.19 }[/tex]
[tex]\frac{345.0 \ mol \ FeCl_3}{162.19 }[/tex]
Divide.
[tex]2.12713484 \ mol \ FeCl_3[/tex]
3. Round
The original measurement of grams, 345.0, has 4 significant figures. We must round our answer to 4 sig figs.
For the answer we calculated, that is the thousandth place.
The 1 in the ten thousandth place tells us to leave the 7 in the thousandth place.
[tex]\approx 2.127 \ mol \ FeCl_3[/tex]
There are about 2.127 moles of iron (III) chloride in 345.0 grams.
