The empirical formula of a certain acid is CH₂O. Whatis the molecular formula, if the molar mass is 90.0 g/mol?
The empirical formula CH₂O has a total molar mass of:
1 carbon atom (12.01 g/mol) + 2 hydrogen atoms (1.01 g/mol x 2) + 1 oxygen atom (16.00 g/mol) = 30.03 g/mol
To find the molecular formula, we need to know how many times this molar mass goes into the given molar mass of 90.0 g/mol:
90.0 g/mol ÷ 30.03 g/mol = 2.998...
This is very close to 3, so we can assume that the molecular formula is three times the empirical formula:
(C₁H₂O₁) x 3 = C₃H₆O₃
Therefore, the molecular formula of this acid is C₃H₆O₃.
To determine the molecular formula from the empirical formula, we need to know the molar mass of the compound. In this case, the molar mass is given as 90.0 g/mol.
The empirical formula tells us the simplest ratio of the elements present in the compound. In this case, the empirical formula is CH₂O, which means there is one carbon atom, two hydrogen atoms, and one oxygen atom in the compound.
To find the molecular formula, we need to find the actual number of each element present in the compound. We can do this by comparing the molar mass of the empirical formula to the molar mass of the molecular formula.
The molar mass of CH₂O can be calculated as follows:
Carbon (C) has a molar mass of approximately 12.01 g/mol.
Hydrogen (H) has a molar mass of approximately 1.01 g/mol.
Oxygen (O) has a molar mass of approximately 16.00 g/mol.
Molar mass of CH₂O = (1 * 12.01 g/mol) + (2 * 1.01 g/mol) + (1 * 16.00 g/mol) = 30.03 g/mol.
To determine the number of empirical units in the molecular formula, we divide the molar mass of the compound by the molar mass of the empirical formula:
Number of empirical units = Molecular mass / Empirical mass
Number of empirical units = 90.0 g/mol / 30.03 g/mol
Number of empirical units = 3
This means that the molecular formula will have three times the number of atoms compared to the empirical formula.
So, the molecular formula of the acid is:
(CH₂O)ₙ, where n = 3.
Therefore, the molecular formula is C₃H₆O₃.