A compound with the percent composition shown below has a molar mass of 60.10g/mol. Find its molecular formula:
C, 39.97%
H, 13.41%
N, 46.62%
Take a 100 g sample. That gives you
39.97 g C
13.4 g H
46.62 g N
Convert to mols.
39.97/12 = mols C
13.41/1 = mols H
46.62/14 = mols N.
Now find the ratio of the elements to each other with the smallest being 1.00. The easy way to do that is to divide the smallest number by itself, then divide the other numbers by that same small number.
Post your work if you get stuck.
Sorry for the intrusion, chemistry: timecode 6:44 I gave K one of your previous answers but it didn't suffice...
C H N
MASS 39.97g 13.41g 46.62
#mol 3.33 13.41 3.33
ratio 1 4 1
empirical formular CH4N
empirical mass 30
(CH4N)2=C2H8N2
THUS THE MOLECULAR FORMULA
To find the molecular formula of a compound, we first need to determine the empirical formula. The empirical formula represents the simplest ratio of the elements present in a compound.
To determine the empirical formula, we need to convert the percent composition of each element to moles.
1. Start by assuming we have 100g of the compound. This assumption allows us to directly convert the percent composition to grams.
C = 39.97g
H = 13.41g
N = 46.62g
2. Convert the mass of each element to moles. To do this, divide the mass of each element by its molar mass.
C: (39.97g) / (12.01g/mol) ≈ 3.33 mol
H: (13.41g) / (1.01g/mol) ≈ 13.27 mol
N: (46.62g) / (14.01g/mol) ≈ 3.33 mol
3. Find the simplest ratio of the moles of each element.
C : H : N ≈ 3.33 : 13.27 : 3.33
4. Divide each mole value by the smallest mole value to obtain the simplest whole-number ratio.
C : H : N ≈ 1 : 5 : 1
Therefore, the empirical formula of the compound is CH5N.
To find the molecular formula, we need to know the molar mass of the compound. In this case, it is given as 60.10g/mol.
1. Calculate the empirical formula mass by adding up the molar masses of the elements in the empirical formula.
CH5N:
C: 1(12.01g/mol) = 12.01g/mol
H: 5(1.01g/mol) = 5.05g/mol
N: 1(14.01g/mol) = 14.01g/mol
Empirical formula mass = 12.01g/mol + 5.05g/mol + 14.01g/mol = 31.07g/mol
2. Determine the factor by which the empirical formula mass needs to be multiplied to match the given molar mass (60.10g/mol).
Factor = (Molar mass) / (Empirical formula mass)
= 60.10g/mol / 31.07g/mol ≈ 1.93
3. Multiply the subscripts in the empirical formula by the factor calculated in the previous step to obtain the molecular formula.
CH5N (empirical formula) * 1.93 = C1.93H9.65N1.93
Since we can't have fractional subscripts in molecular formulas, we round the subscripts to the nearest whole number.
Therefore, the molecular formula of the compound is C2H10N2.