3.Empirical formula is C4H5N2O.Its molecular weight is 194.19g/mole.The "empirical formula weight is about 97.1g/mole.What is the molecular formula ?
Empirical mass = ??. Just add up the atomic masses of each element from the periodic table.
molar mass = empirical mass x a number.
How do you find the number? It is 97.1/empirical mass and round that to a whole number. You will note that the problem lists the molar mass as "about" 97.1 so when you divide you will get a number something like 1.07 or 2.05 or 4.94 and you would round those to 1.00 or 2.00 or 5.00 and that is the number to be used. That number x empirical mass = molar mass (or formula mass).
To find the molecular formula, we need to determine the ratio between the empirical formula weight and the molecular weight.
Molecular formula weight / Empirical formula weight = Molecular formula ratio
Let's substitute the given values:
194.19 g/mol / 97.1 g/mol = 2
This means that the molecular formula is twice the size of the empirical formula.
Now, we need to multiply the subscripts in the empirical formula by 2:
C4H5N2O * 2 = C8H10N4O2
Therefore, the molecular formula is C8H10N4O2.
To determine the molecular formula from the empirical formula and molecular weight, we need to find the ratio between the empirical formula weight and the molecular weight.
The empirical formula weight is the sum of the atomic weights of all the atoms in the empirical formula. In this case, the empirical formula is C4H5N2O. Let's calculate the empirical formula weight:
Empirical formula weight (C4H5N2O) = (4 * atomic weight of C) + (5 * atomic weight of H) + (2 * atomic weight of N) + (1 * atomic weight of O)
To calculate the empirical formula weight, we need to know the atomic weights of carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). Let's assume the atomic weights are:
- Atomic weight of C = 12 g/mole
- Atomic weight of H = 1 g/mole
- Atomic weight of N = 14 g/mole
- Atomic weight of O = 16 g/mole
Substituting these values into the formula, we get:
Empirical formula weight (C4H5N2O) = (4 * 12) + (5 * 1) + (2 * 14) + (1 * 16)
= 48 + 5 + 28 + 16
= 97 g/mole (approximately)
Now, since we know the molecular weight is 194.19 g/mole, we can find the ratio between the molecular weight and the empirical formula weight:
Ratio = Molecular weight / Empirical formula weight
= 194.19 g/mole / 97 g/mole
≈ 2
The ratio is approximately 2, which means the molecular formula contains twice the number of atoms compared to the empirical formula.
To find the molecular formula, we multiply the subscripts in the empirical formula by the ratio:
Molecular formula = (C4H5N2O)2
= C8H10N4O2
Therefore, the molecular formula is C8H10N4O2.