뒤로Molar Mass, Mole Calculations, and Chemical Composition: Applications in GOB Chemistry
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Mole Calculations and Chemical Composition
Molecular Formula and Molar Mass
Understanding the molecular formula and molar mass of a compound is fundamental in chemistry, as these concepts allow chemists to relate the mass of a substance to the number of particles (atoms or molecules) it contains.
Molecular Formula: The molecular formula shows the exact number and type of atoms in a molecule. For example, dipyrithione has the formula C10H8N2O2S2.
Molar Mass: The molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in the molecular formula.
Example Calculation:
For dipyrithione (C10H8N2O2S2):
Carbon (C): 10 atoms × 12.01 g/mol = 120.10 g/mol
Hydrogen (H): 8 atoms × 1.008 g/mol = 8.064 g/mol
Nitrogen (N): 2 atoms × 14.01 g/mol = 28.02 g/mol
Oxygen (O): 2 atoms × 16.00 g/mol = 32.00 g/mol
Sulfur (S): 2 atoms × 32.07 g/mol = 64.14 g/mol
Total molar mass = 120.10 + 8.064 + 28.02 + 32.00 + 64.14 = 252.32 g/mol
Calculating Moles from Mass
The number of moles in a given mass of a substance can be calculated using the formula:
Example: To find the number of moles in 10.0 g of a compound with a molar mass of 252.32 g/mol:
Application: Dipyrithione in Dandruff Shampoo
Dipyrithione is used as an antibacterial and antifungal agent. The following questions illustrate how to apply mole and mass relationships to real-world chemical problems.
What is the molar mass of dipyrithione?
As calculated above, the molar mass is 252.32 g/mol.
How many moles of dipyrithione are in 25.0 g?
How many moles of C are in 25.0 g of dipyrithione?
First, calculate moles of dipyrithione: 0.0991 mol (from above).
Each mole of dipyrithione contains 10 moles of C.
How many moles of dipyrithione contain atoms of N?
Each mole of dipyrithione contains 2 moles of N atoms.
Number of N atoms per mole of dipyrithione: atoms N per mole.
Summary Table: Dipyrithione Calculations
Quantity | Value | Formula Used |
|---|---|---|
Molar mass of dipyrithione | 252.32 g/mol | Sum of atomic masses |
Moles in 25.0 g | 0.0991 mol | |
Moles of C in 25.0 g | 0.991 mol | 0.0991 mol × 10 |
Moles of dipyrithione for N atoms | 6.81 mol |
Key Terms
Mole (mol): The SI unit for amount of substance, representing particles (Avogadro's number).
Molar Mass: The mass of one mole of a substance, in grams per mole.
Molecular Formula: The actual number of each type of atom in a molecule.
