a hydrated iron chloride compound was found to contain 20.66% Fe, 39.35% Cl, and 39.99% water, determine the empirical formula of this hydrated compound
assume 100 grams
20.66 grams Fe=xxx moles Fe
39.35 frams Cl=yyy moles Cl
39.44 grams water=zzz moles H2O
determine xxx,yyyy,zzzz
then divide all be the lowest of the three.
the resultant numbers should give you the subscripts
To determine the empirical formula of the hydrated iron chloride compound, we need to find the ratio of atoms present in the compound.
Step 1: Convert the percentage of each element into grams.
Given:
- Fe: 20.66%
- Cl: 39.35%
- H₂O (water): 39.99%
Assume we have 100g of the compound:
- Fe: 20.66g
- Cl: 39.35g
- H₂O (water): 39.99g
Step 2: Convert the grams of each element into moles.
Using the atomic masses:
- Fe (iron): 55.845 g/mol
- Cl (chlorine): 35.453 g/mol
- H₂O (water): 18.01528 g/mol (2 H + 16 O)
Calculating the moles:
- Moles of Fe = 20.66 g / 55.845 g/mol ≈ 0.3697 mol
- Moles of Cl = 39.35 g / 35.453 g/mol ≈ 1.1108 mol
- Moles of H₂O = 39.99 g / 18.01528 g/mol ≈ 2.2206 mol
Step 3: Find the simplest mole ratio.
Divide the moles of each element by the smallest number of moles. In this case, the smallest number of moles is 0.3697 mol.
- Fe: 0.3697 mol / 0.3697 mol ≈ 1 mol
- Cl: 1.1108 mol / 0.3697 mol ≈ 3 mol
- H₂O: 2.2206 mol / 0.3697 mol ≈ 6 mol
The empirical formula of the hydrated iron chloride compound is FeCl₃ · 6H₂O.
To determine the empirical formula of the hydrated iron chloride compound, we need to calculate the ratio of atoms in the compound.
Step 1: Convert the percentage composition into grams.
Given:
Mass of Fe = 20.66%
Mass of Cl = 39.35%
Mass of H2O = 39.99%
Assuming we have 100g sample, we can convert the percentages to grams:
Mass of Fe = (20.66 / 100) * 100g = 20.66g
Mass of Cl = (39.35 / 100) * 100g = 39.35g
Mass of H2O = (39.99 / 100) * 100g = 39.99g
Step 2: Convert the mass of each element to moles using their molar masses.
Molar mass of Fe = 55.845 g/mol
Molar mass of Cl = 35.453 g/mol
Molar mass of H2O = 18.015 g/mol
Moles of Fe = Mass of Fe / Molar mass of Fe = 20.66g / 55.845 g/mol = 0.3697 mol
Moles of Cl = Mass of Cl / Molar mass of Cl = 39.35g / 35.453 g/mol = 1.1106 mol
Moles of H2O = Mass of H2O / Molar mass of H2O = 39.99g / 18.015 g/mol = 2.2200 mol
Step 3: Divide each mole value by the smallest mole value to get the simplest whole number ratio.
Dividing each mole value by 0.3697 (the smallest value) gives us:
Fe: 0.3697 / 0.3697 = 1
Cl: 1.1106 / 0.3697 = 3
H2O: 2.2200 / 0.3697 = 6
Step 4: Write the empirical formula using the obtained ratios.
The empirical formula of the hydrated iron chloride compound is FeCl3·6H2O, which indicates that there is 1 iron atom, 3 chlorine atoms, and 6 water molecules in the compound.