Calculate the empirical formula of a molecule with the following percent compositions: 55.0% gallium (Ga) and 45.0% fluorine (F).
mass of 100g #of Moles in 100g
of the compound
Ga55.0% _____ ______
F45.0% ______ _______
c. Determine the molecular formula of a molecule having an empirical formula of NH2 and a molar mass of 32 g/mol.
Take a 100 g sample which will give you
55.0 g Ga and
45.0 g F
Convert to mols.
55.0/atomic mass Ga = ?
45.0/atomic mass F = ?
Now find the ratio of the elements to each other with the smallest being 1.00. The easy way to do this is to divide the smaller number by itself(which gives 1.00), then divide the other number by the same small number. Round to whole numbers. Post your work if you get stuck.
c.
empirical formula = NH2. empirical formula mass = 14 + 2(1.00) = 16
molar mass = 32
16*n = 32
n = 2; therefore, the molecule consists of two units of NH2.
(NH2)2 or N2H4.
Check. 2N + 4H = 2(14) + 4(1) = 28 + 4 = 32. must be right.
since i don't have a teacher. I tried and this is what i came up with.
55.0/atomic massGa
55.0/69.723= 1.27 (rounded)
45.0/atomic massF
45.0/18.998404= 2.37 (rounded)
If this is corect what do I do after this. If not can you help me with an headstart please.?
To calculate the empirical formula of the molecule with the given percent compositions, we need to determine the moles of each element in 100g of the compound.
Let's assume we have 100g of the compound.
a. Calculating the moles of gallium (Ga):
Mass of gallium = 55.0g
Molar mass of gallium (Ga) = 69.72 g/mol (from the periodic table)
Moles of gallium (Ga) = Mass of gallium / Molar mass of gallium
= 55.0g / 69.72 g/mol
= 0.7896 mol
b. Calculating the moles of fluorine (F):
Mass of fluorine = 45.0g
Molar mass of fluorine (F) = 18.998 g/mol (from the periodic table)
Moles of fluorine (F) = Mass of fluorine / Molar mass of fluorine
= 45.0g / 18.998 g/mol
= 2.3688 mol
Now, we need to find the simplest whole number ratio of moles between the elements Ga and F.
Divide both moles by the smaller number of moles (0.7896 mol in this case):
Ga moles = 0.7896 mol / 0.7896 mol = 1
F moles = 2.3688 mol / 0.7896 mol = 3
The simplest whole number ratio of moles between Ga and F is 1:3. Therefore, the empirical formula of the molecule is GaF3.
c. To determine the molecular formula of a molecule with an empirical formula of NH2 and a molar mass of 32 g/mol, we need to know the molar mass of each element.
Molar mass of N = 14.01 g/mol (from the periodic table)
Molar mass of H = 1.008 g/mol (from the periodic table)
The empirical formula NH2 has a molar mass of (14.01 g/mol) + (2 * 1.008 g/mol) = 16.026 g/mol.
To find the molecular formula, divide the molar mass of the molecule (32 g/mol) by the molar mass of the empirical formula (16.026 g/mol) to find the scaling factor:
Scaling factor = 32 g/mol / 16.026 g/mol ≈ 1.996
Since the scaling factor is approximately 2, we can multiply the empirical formula NH2 by 2 to get the molecular formula:
Molecular formula = (NH2)2 = N2H4
To calculate the empirical formula of a compound, we need to determine the ratio of atoms present in the compound. This can be done by converting the percent compositions to moles and then dividing by the smallest number of moles obtained.
For the first question, we have the following percent compositions:
Ga (gallium) - 55.0%
F (fluorine) - 45.0%
To determine the moles of gallium (Ga) in 100g of the compound, we use the formula:
moles = (mass of element in grams) / (molar mass of element)
The molar mass of gallium (Ga) is 69.72 g/mol.
moles of Ga = (55.0 g) / (69.72 g/mol) = 0.788 mol
To determine the moles of fluorine (F) in 100g of the compound, we use the formula:
moles = (mass of element in grams) / (molar mass of element)
The molar mass of fluorine (F) is 18.998 g/mol.
moles of F = (45.0 g) / (18.998 g/mol) = 2.37 mol
Next, we divide the number of moles obtained by the smallest number of moles to find the ratio of atoms. In this case, the smallest number of moles is 0.788, which rounds to 0.79 mol.
Ratio of Ga atoms = (0.788 mol) / 0.79 mol ≈ 1
Ratio of F atoms = (2.37 mol) / 0.79 mol ≈ 3
Therefore, the empirical formula for the compound with 55.0% Gallium and 45.0% Fluorine is GaF3.
For the second question, given the empirical formula NH2 and the molar mass of 32 g/mol, we can calculate the molar mass of the empirical formula.
The molar mass of nitrogen (N) is 14.007 g/mol, and the molar mass of hydrogen (H) is 1.008 g/mol.
Molar mass of NH2 = (14.007 g/mol) + (2 * 1.008 g/mol) = 16.023 g/mol
To determine the molecular formula, we need to find the ratio between the molar mass of the empirical formula and the given molar mass.
Ratio = molar mass of the compound / molar mass of the empirical formula
Ratio = (32 g/mol) / (16.023 g/mol) ≈ 1.997
Since the ratio is close to 2, the molecular formula is twice the empirical formula.
Therefore, the molecular formula for a compound with the empirical formula NH2 and a molar mass of 32 g/mol is N2H4.