Percent Composition

How do you determine the empirical formula from a molecular formula?

• By multiplying the subscripts in the molecular formula by their greatest common divisor.

• By dividing the subscripts in the molecular formula by their greatest common divisor.

• By adding the subscripts in the molecular formula together.

• By subtracting the subscripts in the molecular formula from each other.

What is the difference between empirical and molecular formulas?

• The empirical formula shows the actual number of atoms in a molecule, while the molecular formula shows the simplest ratio of elements.

• The empirical formula shows the simplest ratio of elements, while the molecular formula shows the actual number of atoms of each element in a molecule.

• The empirical formula is used for ionic compounds, while the molecular formula is used for covalent compounds.

• The empirical formula represents the total mass of a compound, while the molecular formula represents the volume of a compound.

How many moles are in 2.85 x 10^20 atoms of iron?

• 4.73 x 10^-4 moles

• 1.00 x 10^-3 moles

• 2.50 x 10^-4 moles

• 5.00 x 10^-4 moles

How do you find the percent by mass of an element in a compound?

• Percent by mass = (mass of element in 1 mole of compound / molar mass of compound) x 100.

• Percent by mass = (molar mass of compound / mass of element in 1 mole of compound) x 100.

• Percent by mass = (mass of element in compound / total mass of all elements) x 100.

• Percent by mass = (mass of element in compound / molar mass of element) x 100.

How do you convert atoms to moles?

• moles = number of atoms / Avogadro's number (6.022 x 10^23)

• moles = number of atoms x Avogadro's number (6.022 x 10^23)

• moles = number of atoms + Avogadro's number (6.022 x 10^23)

• moles = number of atoms - Avogadro's number (6.022 x 10^23)

What is a common mistake when calculating percent composition?

• Forgetting to use the total mass of the compound in the denominator when calculating percent composition.

• Using the mass of only one element instead of the total mass of the compound.

• Calculating the percent composition without knowing the molecular formula.

• Dividing the mass of the compound by the number of elements present.

What is the significance of percent composition in chemistry?

• It helps in understanding the composition of compounds and is essential for stoichiometric calculations.

• It determines the color of compounds in solution.

• It is used to measure the temperature of chemical reactions.

• It indicates the volatility of a substance.

How do you find the empirical formula from percent composition?

• Convert the percent composition to grams, then to moles, and divide by the smallest number of moles to find the ratio.

• Multiply the percent composition by the molar mass of each element.

• Add the percentages together to get a total mass.

• Use the percent composition to directly write the empirical formula.

What is percent composition?

• The total mass of a compound divided by the number of elements in it.

• The percentage by mass of each element in a compound, calculated by dividing the mass of the element by the total mass of the compound and multiplying by 100.

• The ratio of the mass of a compound to its volume.

• The mass of a compound expressed as a percentage of its molecular weight.

Why is it important to know the empirical formula?

• It helps in determining the simplest ratio of elements, which is useful in chemical reactions and stoichiometry.

• It provides the exact number of atoms in a molecule.

• It is used to calculate the molecular weight of a compound.

• It helps in identifying the color of the compound.