The density of water is 1.00g/ml at 4 degrees Celsius. How many water molecules are present in 2.56ml of water at this temperature?

8.55x10^22 molecules

Explanation:

From the question given, the following data were obtained:

Density = 1g/mL

Volume = 2.56mL

Mass = ?

Density = Mass / volume

Mass = Density x volume

Mass = 1 x 2.56

Mass = 2.56g

Now let us convert this mass (i. e 2.56g) of water to mole

Molar Mass of H2O = (2x1) + 16 = 2 + 16 = 18g/mol

Mass of H2O = 2.56g

Number of mole of H2O=? Number of mole = Mass / Molar Mass

Number of mole of H2O = 2.56/18

Number of mole of H2O = 0.142mol

From Avogadro's hypothesis, 1mole of any substance contains 6.02x10^23 molecules. This means that 1mole of H2O contains 6.02x10^23 molecules.

Now if 1mole of H2O contains 6.02x10^23 molecules, then 0.142mol of H2O will contain = 0.142 x 6.02x10^23 = 8.55x10^22 molecules