a) How many moles are there in 24 grams of FeF?
b) How many molecules are there in 450 grams of Na₂SO₄?
c) How many moles are there in 2.3 x 10 atoms of Silver (Ag)?
d) How many grams are there in 7.4 x 10″ moles of AgNO,?
The Correct Answer and Explanation is :
Let’s address each of your questions step by step:
a) How many moles are there in 24 grams of FeF?
It seems there might be a typographical error in your query, as “FeF” is not a common chemical formula. Perhaps you intended to refer to iron(III) fluoride, which has the chemical formula FeF₃. Assuming this is the case, we can calculate the number of moles in 24 grams of FeF₃.
First, determine the molar mass of FeF₃ by summing the atomic masses of its constituent elements:
- Iron (Fe): 55.845 g/mol
- Fluorine (F): 18.998 g/mol
Since there are three fluorine atoms in the compound:
Molar mass of FeF₃ = 55.845 g/mol + 3 × 18.998 g/mol = 112.839 g/mol
Next, use the formula:
Number of moles = Mass (g) / Molar mass (g/mol)
For 24 grams of FeF₃:
Number of moles = 24 g / 112.839 g/mol ≈ 0.213 moles
b) How many molecules are there in 450 grams of Na₂SO₄?
To find the number of molecules, we first calculate the number of moles and then use Avogadro’s number to convert moles to molecules.
The molar mass of sodium sulfate (Na₂SO₄) is calculated as follows:
- Sodium (Na): 22.989769 g/mol × 2 = 45.979538 g/mol
- Sulfur (S): 32.065 g/mol
- Oxygen (O): 15.999 g/mol × 4 = 63.996 g/mol
Total molar mass of Na₂SO₄ = 45.979538 g/mol + 32.065 g/mol + 63.996 g/mol = 142.040538 g/mol
Number of moles = 450 g / 142.040538 g/mol ≈ 3.168 moles
Using Avogadro’s number (6.022 × 10²³ molecules/mol):
Number of molecules = 3.168 moles × 6.022 × 10²³ molecules/mol ≈ 1.91 × 10²⁴ molecules
c) How many moles are there in 2.3 × 10¹⁰ atoms of Silver (Ag)?
To convert atoms to moles, divide the number of atoms by Avogadro’s number:
Number of moles = Number of atoms / Avogadro’s number
Number of moles = 2.3 × 10¹⁰ atoms / 6.022 × 10²³ atoms/mol ≈ 3.82 × 10⁻¹⁴ moles
d) How many grams are there in 7.4 × 10¹⁰ moles of AgNO₃?
First, calculate the molar mass of silver nitrate (AgNO₃):
- Silver (Ag): 107.8682 g/mol
- Nitrogen (N): 14.0067 g/mol
- Oxygen (O): 15.999 g/mol × 3 = 47.997 g/mol
Total molar mass of AgNO₃ = 107.8682 g/mol + 14.0067 g/mol + 47.997 g/mol = 169.8719 g/mol
To find the mass corresponding to 7.4 × 10¹⁰ moles:
Mass (g) = Number of moles × Molar mass (g/mol)
Mass = 7.4 × 10¹⁰ moles × 169.8719 g/mol ≈ 1.26 × 10¹³ grams
Explanation:
In chemistry, the mole is a fundamental unit used to quantify the amount of a substance. One mole corresponds to Avogadro’s number (6.022 × 10²³) of entities, whether they are atoms, molecules, ions, or other particles. This large number provides a bridge between the atomic scale and the macroscopic scale we observe.
The molar mass of a compound is the mass of one mole of that substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms present in the molecular formula. For instance, the molar mass of FeF₃ is derived from adding the atomic mass of one iron atom and three fluorine atoms.
To determine the number of moles from a given mass, divide the mass by the molar mass. Conversely, to find the mass from a given number of moles, multiply the number of moles by the molar mass. When converting between the number of particles (atoms or molecules) and moles, Avogadro’s number serves as the conversion factor.
These calculations are essential in stoichiometry, allowing chemists to predict the outcomes of chemical reactions, determine reactant quantities, and analyze compounds’ compositions. Accurate molar mass determination and mole calculations are foundational skills in chemistry, enabling precise formulation and understanding of chemical processes.
Understanding these concepts ensures accurate measurements and predictions in chemical experiments and industrial applications, highlighting the importance of the mole as a central unit in chemical quantification.