The persentage composition of acitic acid is found to be 3.99%C of 6.7%H and 53.4%O and it molecular mass was determined by experiment to be 60
Calculate the emperical formula and molecular formula?
To determine the empirical formula, we need to find the ratios of the elements in the compound.
Given:
%C = 3.99%
%H = 6.7%
%O = 53.4%
Convert the percentages to grams:
%C: 3.99 g
%H: 6.7 g
%O: 53.4 g
Next, we need to convert the grams of each element to moles.
Convert grams of carbon to moles:
C: 3.99 g
Molar mass of carbon (C): 12.01 g/mol
Moles of carbon = grams of carbon / molar mass of carbon
Moles of carbon = 3.99 g / 12.01 g/mol = 0.3322 mol
Convert grams of hydrogen to moles:
H: 6.7 g
Molar mass of hydrogen (H): 1.01 g/mol
Moles of hydrogen = grams of hydrogen / molar mass of hydrogen
Moles of hydrogen = 6.7 g / 1.01 g/mol = 6.6327 mol
Convert grams of oxygen to moles:
O: 53.4 g
Molar mass of oxygen (O): 16.00 g/mol
Moles of oxygen = grams of oxygen / molar mass of oxygen
Moles of oxygen = 53.4 g / 16.00 g/mol = 3.3375 mol
Now, divide each mole value by the smallest mole value to find the simplest whole number ratio.
Smallest mole value = 0.3322 mol (carbon)
C: 0.3322 mol / 0.3322 mol = 1
H: 6.6327 mol / 0.3322 mol = 19.928 (approximately 20)
O: 3.3375 mol / 0.3322 mol = 10.05 (approximately 10)
The empirical formula is therefore CH2O.
To determine the molecular formula, we need to know the molar mass of the compound.
Given: Molecular mass of the compound = 60 g/mol
Calculate the empirical formula mass:
C: 12.01 g/mol * 1 atom = 12.01 g/mol
H: 1.01 g/mol * 2 atoms = 2.02 g/mol
O: 16.00 g/mol * 1 atom = 16.00 g/mol
Empirical formula mass = 12.01 g/mol + 2.02 g/mol + 16.00 g/mol = 30.03 g/mol
To find the molecular formula, divide the molecular mass by the empirical formula mass:
Molecular formula mass = 60 g/mol
Empirical formula mass = 30.03 g/mol
Molecular formula mass / Empirical formula mass = 60 g/mol / 30.03 g/mol = 1.998
Round the ratio to the nearest whole number:
1.998 (approximately 2)
The molecular formula is therefore (CH2O)2 or C2H4O2.