2.1.4 - Acids Flashcards
What is an empirical formula?
The empirical formula represents the simplest whole-number ratio of elements in a compound.
What is a molecular formula?
The molecular formula shows the actual number of atoms of each element in a molecule of a compound.
How do the empirical formula and molecular formula differ?
The empirical formula gives the simplest ratio of elements, whereas the molecular formula gives the exact number of atoms of each element in a molecule.
How do you calculate the empirical formula from experimental data?
1- Convert the masses of elements into moles by dividing by their molar masses.
2- Find the simplest whole-number ratio by dividing each mole value by the smallest number of moles.
What is the first step in calculating the empirical formula of a compound?
The first step is to convert the masses of each element in the compound into moles by dividing the mass by the element’s molar mass.
How do you determine the simplest whole-number ratio of elements in a compound?
Divide each of the mole values by the smallest number of moles calculated. This gives the simplest ratio of atoms.
What if the mole ratio of elements does not give whole numbers?
If the ratio is not a whole number, multiply all values by the same factor to convert them into whole numbers (e.g., 1.5 can be multiplied by 2 to get 3).
How do you calculate the molecular formula from the empirical formula?
The molecular formula can be found by multiplying the empirical formula by a factor that is the ratio of the molar mass of the compound to the molar mass of the empirical formula.
Factor = (Molar mass of compound) / (Molar mass of empirical formula)
What is the molar mass of a compound?
The molar mass is the sum of the relative atomic masses of the elements in a compound, expressed in g/mol.
What is the relationship between the empirical formula and the molecular formula?
The empirical formula represents the simplest ratio of elements, while the molecular formula gives the actual number of atoms of each element. The molecular formula is a multiple of the empirical formula.
How do you find the empirical formula of a compound from the percentage composition?
1- Assume you have 100g of the compound, so the percentages are the masses.
2- Convert the masses of each element to moles.
3- Divide by the smallest number of moles to get the simplest ratio.
How do you calculate the molar mass of a compound from its empirical formula?
The molar mass of a compound is the sum of the relative atomic masses of the elements in the empirical formula. For example, for CH₂O, the molar mass is 12 + (2 × 1) + 16 = 30 g/mol.
What is the formula for calculating the empirical formula using masses of elements?
1- Convert the mass of each element to moles:
Moles = Mass (g) / Molar mass (g/mol)
2- Divide the number of moles by the smallest number of moles to get the simplest whole-number ratio.
How do you calculate the molecular formula if you know the empirical formula and the molar mass?
1- Calculate the molar mass of the empirical formula.
2- Divide the molar mass of the compound by the molar mass of the empirical formula.
3- Multiply the empirical formula by this factor to get the molecular formula.
How do you convert percentage composition into an empirical formula?
1- Assume a 100g sample, so percentages become grams.
2- Convert grams to moles using molar masses.
3- Find the smallest mole value, then divide all moles by that value to get the simplest ratio.
What is an example of how to calculate the empirical formula of a compound?
1- For a compound with 40% carbon, 6.7% hydrogen, and 53.3% oxygen, assume 100g of the compound.
2- Convert each percentage into grams: 40g C, 6.7g H, 53.3g O.
3- Convert grams to moles:
C: 40g / 12 g/mol = 3.33 mol
H: 6.7g / 1 g/mol = 6.7 mol
O: 53.3g / 16 g/mol = 3.33 mol
4- Divide all by the smallest value (3.33 mol) to get the ratio: C₁H₂O₁, which is the empirical formula CH₂O.
What is the difference between empirical and molecular formula?
The empirical formula is the simplest ratio of elements, while the molecular formula gives the actual number of atoms of each element in a molecule. The molecular formula is a multiple of the empirical formula.
How is the empirical formula related to molecular weight?
The molecular formula is derived from the empirical formula by multiplying it by a whole number factor, which is the ratio of the compound’s molecular weight to the empirical formula weight.
What if the empirical formula and molecular formula are the same?
If the empirical formula and molecular formula are the same, it means the compound’s molecular structure is already in its simplest form.
Can the empirical formula represent the actual molecular structure?
No, the empirical formula only shows the simplest ratio of atoms. The molecular formula gives the actual number of atoms and represents the true structure.
How does the empirical formula relate to the chemical properties of a compound?
The empirical formula gives insight into the simplest ratio of elements, but the chemical properties of a compound depend on the molecular structure and the arrangement of atoms, which is described by the molecular formula.
How do you handle fractional values in the mole ratio when calculating the empirical formula?
If a mole ratio is fractional (e.g., 1:1.5), multiply all the values by the smallest integer to eliminate the fraction (in this case, multiply by 2 to get a ratio of 2:3).
How do you calculate the molecular formula if you know the empirical formula CH₂O and the molar mass of the compound is 180 g/mol?
1- Molar mass of empirical formula CH₂O = 30 g/mol.
2- 180 g/mol / 30 g/mol = 6.
3- Multiply the empirical formula CH₂O by 6 to get the molecular formula C₆H₁₂O₆.
What is percent composition?
Percent composition is the percentage by mass of each element in a compound, calculated by dividing the mass of each element by the molar mass of the compound and multiplying by 100.
