A tablespoon holds 0.5 mole of water. What is the number of molecules present in it?

The number of molecules in a substance is determined by the mole concept. According to Avogadro's law, one mole of any substance contains approximately 6.022 × 1023 particles (atoms, molecules, or ions). This constant is known as Avogadro's number (NA).

To find the number of molecules in 0.5 mole of water (H2O), we use the formula:

Number of molecules = moles × NA

Substituting the given values:

0.5 × 6.022 × 1023 = 3.011 × 1023

Therefore, 0.5 mole of water contains 3.01 × 1023 molecules. Option A represents the number of molecules in one full mole, while options C and D are incorrect numerical values unrelated to the Avogadro constant.