Final answer:
To calculate the number of lactic acid molecules in 5.0 g, first find the molar mass of lactic acid and then use the mass and molar mass to determine the number of moles. Multiply the moles by Avogadro's number to get approximately 3.34 × 10^22 molecules of lactic acid.
Step-by-step explanation:
The question is asking how many molecules of lactic acid are present in 5.0 g of the substance. To find this, we first need to calculate the molar mass of lactic acid (C3H6O3). We do this by summing the atomic masses of its constituent atoms:
- C (12.0 g/mol) × 3 = 36.0 g/mol
- H (1.008 g/mol) × 6 = 6.048 g/mol
- O (16.0 g/mol) × 3 = 48.0 g/mol
Adding these together gives us a molar mass of 90.048 g/mol for lactic acid. Then, we will use the following stoichiometric relation:
number of moles = mass (g) / molar mass (g/mol)
For 5.0 g of lactic acid:
number of moles = 5.0 g / 90.048 g/mol
= 0.0555 moles
Lastly, to find the number of molecules, we multiply the number of moles by Avogadro's number
(6.022 × 1023 molecules/mol):
number of molecules = 0.0555 moles × 6.022 × 1023 molecules/mol
= 3.34 × 1022 molecules
Therefore, 5.0 g of lactic acid in the leg muscles corresponds to approximately 3.34 × 1022 molecules.