The molecular formulas of the empirical ones of P₂O₅ and CH₂O are P₄O₁₀ and C₇H₁₄O₇, respectively, knowing that their molar masses are 310 and 200.18 g/mol, respectively.
<h3>1. Molecular formula of P₂O₅</h3>We can calculate the molecular formula as follows:
(1)
Where:
- MF: is the molecular formula
- EF: is the empirical formula
- n: is an integer
To calculate the integer <em>n</em>, we need to use the following equation:
(2)
Where:
- M: is the molar mass of P₂O₅ = 310 g/mol
: is the molar mass of the empirical formula
The molar mass of the empirical formula of P₂O₅ is given by:
Where:
: is the atomic weight of phosphorus = 30.974 g/mol
: is the <em>atomic weight</em> of oxygen = 15.999 g/mol
So, the <em>molar mass</em> of the <em>empirical formula</em> of P₂O₅ is:
Now, we can find the integer <em>n </em>(eq 2).
Finally, after multiplying the integer <em>n</em> by the number of atoms on the empirical formula of P₂O₅, we have (eq 1):
Therefore, the molecular mass of P₂O₅ is P₄O₁₀.
<h3>2. Molecular formula of CH₂O </h3>We know:
- M: molar mass of CH₂O = 200.18 g/mol
To calculate the integer <em>n</em> and so the molecular mass of the molecule, we need to calculate the<em> molar mass</em> of the <em>empirical formula</em> of CH₂O.
Now, the integer <em>n </em>is equal to (eq 2):
Finally, the molecular formula of the molecule is (eq 1):
Therefore, the molecular formula of CH₂O is C₇H₁₄O₇.
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