A compound which contains hydrogen, oxygen, carbon only has molar mass of about 85 g/mol. When 0.43 g of the compound is burned in excess of oxyfen, 1.10 g of CO2 and 0.45 g of H2O are formed. Find the molecular formula and the empirical formula of the compound
g C = g CO2 x (atomic mass C/molar mass CO2) = 1.10 x 12/44 = about 0.3
g H = g H2O x (2*atomic mass H/molar mass H2O) = about 0.05
g O = 0.43- g H - g C = about 0.08
Convert to mols.
mols C = 0.3/12 = ?
mols H = 0.05/1 = ?
mols O = 0.08/16 = ?
Now find the ratio of these numbers to each other with the smallest being 1.00. The easy way to do that is to divide the smaller numberr by itself, then divide the other numbers by the same small number. Round to whole numbers. I get C5H10O but check all of these numbers to make sure I didn't hit the wrong key of my calculator. That's the empirical formula.
To find the molecular formula, you know the approx molar mass is 85. What's the empirical mass for C5H10O. That will be 5*12 + 10*1 + 16 = 86 so the molecular formula must be 1 unit of the empirical formula; i.e., molecular formula is C5H10O.
To find the molecular formula and the empirical formula of the compound, we need to follow these steps:
Step 1: Determine the number of moles of CO2 and H2O produced.
To find the number of moles, we use the molar mass of each compound.
Molar mass of CO2 = 12.01 g/mol (C) + 2(16.00 g/mol) (O) = 44.01 g/mol
Molar mass of H2O = 2(1.01 g/mol) (H) + 16.00 g/mol (O) = 18.02 g/mol
Moles of CO2 = mass of CO2 / molar mass of CO2 = 1.10 g / 44.01 g/mol
Moles of H2O = mass of H2O / molar mass of H2O = 0.45 g / 18.02 g/mol
Step 2: Convert the moles of CO2 and H2O to the moles of the compound.
Since there is a ratio between the compound and the products CO2 and H2O, we need to find the smallest mole ratio.
Assume the compound has the empirical formula CxHyOz.
From the balanced chemical equation, we know that 1 mole of the compound produces 1 mole of CO2 and 1 mole of H2O.
Therefore, we have:
Moles of compound = Moles of CO2 = Moles of H2O.
Step 3: Calculate the molecular formula of the compound.
The molecular mass of the compound is given as 85 g/mol.
Molecular formula mass = (Empirical formula mass) * n
Where n is the number of empirical formula units in the molecular formula.
To find the value of n, we divide the molecular formula mass by the empirical formula mass and round to the nearest whole number.
n = Molecular formula mass / Empirical formula mass
n = 85 g/mol / empirical formula mass
Step 4: Determine the empirical formula of the compound
To find the empirical formula, we need to find the ratio of atoms in the compound.
From step 1, we know the moles of each element:
Moles of C in the compound = Moles of CO2
Moles of H in the compound = Moles of H2O
Moles of O in the compound = Moles of CO2 + Moles of H2O
Step 5: Convert moles to whole numbers.
If the ratio of moles is not a whole number, multiply each ratio by the smallest possible number to make them all whole numbers.
Step 6: Write the empirical formula using the whole number ratios.
The empirical formula will give you the simplest ratio of the atoms in the compound.
Now that you have the empirical formula, you can calculate the molecular formula using the n value obtained in step 3.
Note: Since the molar mass of the compound is approximately 85 g/mol, the empirical formula mass may not be equal to the molecular formula mass, as the empirical formula gives you the simplest ratio of atoms.
By following these steps, you will be able to find the molecular formula and the empirical formula of the compound.