7.25 g of iron were reacted with sulfur until the product reached a constant mass of 13.50 g. If the experimental molecular mass of the product was measured as 572 u, what is the molecular formula of the product? What is the actual molecular mass of the product?
To determine the molecular formula of the product, we need to follow a few steps:
1. Calculate the number of moles of iron reacted:
The molar mass of iron (Fe) is 55.85 g/mol.
Number of moles of iron = Mass of iron / Molar mass of iron
Number of moles of iron = 7.25 g / 55.85 g/mol = 0.130 moles
2. Determine the ratio of the reactants:
In the balanced chemical equation for the reaction between iron and sulfur, the ratio of the reactants can be obtained.
The balanced equation for the reaction is:
Fe + S -> FeS
From the equation, we can see that 1 mole of iron reacts with 1 mole of sulfur to produce 1 mole of iron sulfide (FeS).
3. Calculate the number of moles of sulfur reacted:
The number of moles of iron sulfide (FeS) produced is equal to the number of moles of sulfur reacted.
Number of moles of sulfur = Number of moles of iron = 0.130 moles
4. Calculate the mass of sulfur reacted:
The molar mass of sulfur (S) is 32.06 g/mol.
Mass of sulfur = Number of moles of sulfur x Molar mass of sulfur
Mass of sulfur = 0.130 moles x 32.06 g/mol = 4.168 g
5. Calculate the mass of the product (iron sulfide):
Mass of product = Mass of iron + Mass of sulfur
Mass of product = 7.25 g + 4.168 g = 11.418 g
6. Calculate the actual molecular mass of the product:
Actual molecular mass = Mass of product / number of moles
Actual molecular mass = 11.418 g / 0.130 moles = 87.83 u
Now we can answer the two questions:
1. What is the molecular formula of the product?
To determine the molecular formula, we need to compare the actual molecular mass and the experimental molecular mass.
Since the experimental molecular mass of the product is 572 u and the actual molecular mass is 87.83 u, we can calculate the ratio of the two masses.
Ratio = Experimental molecular mass / Actual molecular mass
Ratio = 572 u / 87.83 u = 6.51
The ratio of the experimental molecular mass and the actual molecular mass gives us the ratio of the empirical formula to the molecular formula.
If we round the ratio to the nearest whole number, we get 7.
Therefore, the empirical formula of the product is FeS.
2. What is the actual molecular mass of the product?
We have already calculated the actual molecular mass, which is 87.83 u.