Determine the number of moles in 258.45 grams of iron (III) chloride (FeCl3). Show and explain all your work for full credit. Make sure you show all units.

Explanation:

To convert from grams to moles, we must use the molar mass. This can be found on the Periodic Table. First, find the molar mass of iron and chlorine.

Check the formula. There is a subscript of 3 after Cl, so there are 3 atoms of chlorine in 1 molecule. Multiply iron's molar mass by 3, then add iron's molar mass.

Use this number as a ratio.

Multiply by the given number of grams.

Flip the ratio so the grams of iron (III) chloride cancel.

The original measurement of grams has 5 significant figures, so our answer must have the same. For the number we calculated, that is the ten thousandth place.

258.45 grams is approximately 1.5935 moles of iron (III) chloride.