Final answer:
To determine the number of molecules of glucose (C6H12O6) in 25.9 g of the substance, convert the mass of glucose to moles and use Avogadro's number to calculate the number of molecules.
Step-by-step explanation:
To determine the number of molecules of glucose (C₆H₁₂O₆) in 25.9 g of the substance, we need to convert the mass of glucose to moles and then use Avogadro's number to calculate the number of molecules.
First, we calculate the molar mass of glucose: C has a molar mass of 12.01 g/mol, H has a molar mass of 1.008 g/mol, and O has a molar mass of 16.00 g/mol. So, the molar mass of glucose is (6 * 12.01) + (12 * 1.008) + (6 * 16.00) = 180.18 g/mol.
Next, we use the formula: Number of moles = mass / molar mass. Plugging in the values, we have Number of moles = 25.9 g / 180.18 g/mol = 0.1438 mol.
Finally, we use Avogadro's number, 6.022 × 10^23 molecules/mol, to calculate the number of molecules: Number of molecules = Number of moles * Avogadro's number = 0.1438 mol * (6.022 × 10^23 molecules/mol) = 8.665 × 10^22 molecules.