The density of water is 1.00g/mL at 4'C. How many water molecules are present in 2.56mL of water at this temperature?

mromezy12,

To get the molecules, you should first solve how many grams of water are present. So you should multiply the density with the volume.

1.00g/ml times 2.56 ml is equal to 2.56g of water.

then multiply the mass with the molar mass of water. in water there are two hidrogen molecules and 1 oxygen molecule, so the molar mass would be 18.

Deviding 2.56g by 18g would give mole number of the water and to get the number of the molecules, you should times avogdro's number(6.23x10^23).

the answer would be 8.56x10^22