Final answer:
To determine the number of molecules in a 12.4 g sample of H₂SO₄, convert the mass to moles using molar mass and then use Avogadro's number to convert moles to molecules. The number of molecules is approximately 7.58 x 10²².
Step-by-step explanation:
To determine the number of molecules in a 12.4 g sample of H₂SO₄, we need to convert the mass of the sample to moles using the molar mass of H₂SO₄. The molar mass of H₂SO₄ is approximately 98 g/mol. So, the number of moles in the sample is 12.4 g / 98 g/mol = 0.126 moles.
Next, we can use Avogadro's number (6.022 x 10²³) to convert the number of moles to the number of molecules. Each mole of a substance contains 6.022 x 10²³ molecules. Therefore, the number of molecules in the 12.4 g sample of H₂SO₄ is 0.126 moles x (6.022 x 10²³ molecules/mol) = 7.58 x 10²² molecules.