Calculating Molar Mass and Number of Moles (Worked Example)

Overview

• Molar Mass: Mass in grams of 1 mole of a substance.
• Objective: Calculate the number of moles in a 1.52 kilogram sample of glucose (C6H12O6).
• Tools Required: Periodic table of elements.

Key Concepts

• Mole: Quantity represented by Avogadro's number (6.022 x 10^23).
• Molar Mass Calculation: Sum the molar masses of component atoms.

Steps to Calculate Moles

1. Determine Molar Mass of Glucose:

   • Use the periodic table to find molar masses:
     • Carbon (C): 12.01 g/mol
     • Hydrogen (H): 1.008 g/mol
     • Oxygen (O): 16.00 g/mol
   • Calculate molar mass for glucose (C6H12O6):
     • 6 Carbons (6 x 12.01 g/mol)
     • 12 Hydrogens (12 x 1.008 g/mol)
     • 6 Oxygens (6 x 16.00 g/mol)
   • Total Molar Mass of Glucose: 180.16 g/mol

2. Convert Kilograms to Grams:

   • 1.52 kg = 1,520 grams

3. Calculate Number of Moles:

   • Use formula: (\text{Moles} = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}})
   • Moles of glucose = (\frac{1,520 \text{ g}}{180.16 \text{ g/mol}})
   • Result: Approximately 8.44 moles

Significant Figures

• Calculation precision is determined by the least number of decimal places in the initial data.
• Example: Carbon and Oxygen values are used with precision to the hundredths place.

Conclusion

• Successfully calculated the amount of glucose in moles for a given mass based on molar mass derived from atomic weights.