A compound on analysis gave the following results.C= 54.54%. H=9.09% O= 36.37%. And vapour density of compound = 88. Find the molecular of formula of the compound.
Firstly, we need to calculate the empirical formula of the compound:
Assume we have 100g of the compound, then:
C = 54.54g
H = 9.09g
O = 36.37g
Now, we need to convert the masses of the elements into moles:
moles of C = 54.54/12 = 4.55
moles of H = 9.09/1 = 9.09
moles of O = 36.37/16 = 2.27
Next, we need to divide the number of moles of each element by the smallest number of moles:
4.55/2.27 = 2
9.09/2.27 = 4
2.27/2.27 = 1
Therefore, the empirical formula of the compound is C2H4O.
Now we need to find the molecular formula by using the vapour density of the compound.
Molecular weight = 88
Empirical formula weight = (2x12) + (4x1) + 16 = 44
Dividing the molecular weight by the empirical formula weight gives: 88/44 = 2
Therefore, the molecular formula of the compound is (C2H4O)2 which simplifies to C4H8O2.
To find the molecular formula of the compound, we need to determine the empirical formula first. The empirical formula gives us the simplest whole number ratio of the elements present in the compound.
Step 1: Assume we have 100 grams of the compound.
- C = 54.54 g (54.54% of 100g)
- H = 9.09 g (9.09% of 100g)
- O = 36.37 g (36.37% of 100g)
Step 2: Convert grams to moles using the molar mass of each element.
- C: molar mass of carbon (C) = 12.01 g/mol
- H: molar mass of hydrogen (H) = 1.008 g/mol
- O: molar mass of oxygen (O) = 16.00 g/mol
Moles of C = 54.54 g / 12.01 g/mol ≈ 4.54 mol
Moles of H = 9.09 g / 1.008 g/mol ≈ 9.02 mol
Moles of O = 36.37 g / 16.00 g/mol ≈ 2.27 mol
Step 3: Determine the simplest whole number ratio of moles by dividing by the smallest number of moles.
- C: 4.54 mol / 2.27 mol ≈ 2
- H: 9.02 mol / 2.27 mol ≈ 4
- O: 2.27 mol / 2.27 mol = 1
The empirical formula of the compound is C2H4O.
Step 4: Calculate the empirical formula mass.
- Empirical formula mass = (2 * molar mass of C) + (4 * molar mass of H) + (1 * molar mass of O)
- Empirical formula mass = (2 * 12.01 g/mol) + (4 * 1.008 g/mol) + (1 * 16.00 g/mol)
- Empirical formula mass ≈ 44.09 g/mol
Step 5: Calculate the ratio of the molecular formula mass to the empirical formula mass.
- Ratio = Vapour density of the compound / Empirical formula mass
- Ratio = 88 / 44.09 ≈ 1.99
Step 6: Multiply the subscripts in the empirical formula by the ratio calculated in Step 5 to obtain the molecular formula.
- Subscripts in the empirical formula (C2H4O) * 1.99 ≈ C3.98H7.96O
Rounding off the subscripts to the nearest whole numbers, the molecular formula of the compound is C4H8O2.