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How do you calculate sugar molecules?

Published in Chemistry Calculations 2 mins read

You calculate the number of sugar molecules in a sample by first determining the number of moles of sugar present and then multiplying by Avogadro's number.

Here's a breakdown of the steps:

  1. Determine the Mass of the Sugar Sample: You need to know the mass of your sugar sample in grams. This can be done by weighing the sample using a balance.

  2. Identify the Type of Sugar and its Molar Mass: Common table sugar is sucrose (C₁₂H₂₂O₁₁), which has a molar mass of approximately 342.3 g/mol. Other sugars like glucose (C₆H₁₂O₆, molar mass ~180.16 g/mol) or fructose (C₆H₁₂O₆, molar mass ~180.16 g/mol) will have different molar masses. Make sure to use the correct molar mass for the sugar you're working with.

  3. Calculate the Number of Moles: Divide the mass of the sugar sample (in grams) by the molar mass of the sugar (in g/mol). This will give you the number of moles of sugar in your sample.

    • Formula: Moles of Sugar = (Mass of Sugar) / (Molar Mass of Sugar)

  4. Calculate the Number of Molecules: Multiply the number of moles of sugar by Avogadro's number, which is approximately 6.022 x 10²³. Avogadro's number represents the number of molecules (or atoms, ions, etc.) in one mole of a substance.

    • Formula: Number of Molecules = (Moles of Sugar) x (Avogadro's Number)

Example:

Let's say you have a sugar cube of sucrose (C₁₂H₂₂O₁₁) that weighs 5 grams.

  1. Mass of Sugar: 5 grams
  2. Molar Mass of Sucrose: 342.3 g/mol
  3. Moles of Sucrose: 5 g / 342.3 g/mol = 0.0146 mol
  4. Number of Sucrose Molecules: 0.0146 mol x (6.022 x 10²³ molecules/mol) = 8.79 x 10²¹ molecules

Therefore, there are approximately 8.79 x 10²¹ sucrose molecules in the 5-gram sugar cube.

Summary Table:

Step Description Formula
1. Mass of Sugar Measure the mass of the sugar sample. -
2. Molar Mass Identify the sugar and find its molar mass. -
3. Calculate Moles Divide the mass by the molar mass. Moles = Mass / Molar Mass
4. Calculate Molecules Multiply the number of moles by Avogadro's number. Molecules = Moles x Avogadro's Number (6.022 x 10²³)

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